Grade 8 science teacher's guide

UNIT 1
Force, Motion, and Energy

3
UNIT 1: Force, Motion, and Energy
Overview
In Grade 7, students learned that energy exists in different forms and it can
be transformed from one form to another. They also learned that energy can be
transferred from one object or place to another in different ways. In Grade 8,
students deepen their understanding of the different forms of energy by describing
how the energy transferred affects, or is affected by, objects.
This unit has six modules. The first two modules discuss the effects of energy
at the macroscopic level while the next four modules tackle these effects at the
particle level. Module 1 focuses on the idea that if a net or unbalanced force acts on
an object, the motion of the object will change. Module 2 picks up this idea and
explains how the application of force can do work on an object with a corresponding
transfer of energy. Module 3 describes the effects of heat on objects involved in
energy transfer and explains these effects at the particle level. Module 4 deals with
how energy affects the movement of charges in electrical circuits. Module 5
discusses how energy propagates through solids, liquids, and gases. It also
describes how the speed of the energy transferred varies with some factors, such as
temperature. Module 6 describes how the different colors of light differ in terms of
their frequency and energy.
Most of the topics in this module are dealt with qualitatively in order for
students to have a basic understanding of the concepts. Some tasks include
measurements and computations in order to illustrate the relationship among
quantities. Through the activities included in each module, it is also aimed to make
students gain interest in these topics and motivate them to learn more in the
succeeding grade levels.
The following ideas are expected to be developed among the students:
 Energy is transmitted in the form of heat from one place to another due to
temperature differences or in the form of mechanical work (potential and
kinetic energy).
 Energy affects objects. The effects are manifested in the changes that
objects undergo. For example, energy can cause changes in the motion of
objects, particles, or charges. It can also cause changes in some properties
of matter such as temperature. The amount of change depends on the
amount of energy transferred.
 The energy transferred can also be affected by the nature or kind of materials
involved.

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FORCES AND MOTION
After learning about the ways by which the motion of an object can be
described and represented in grade 7, students will now study the motion of objects
using the concept of force. They will describe the effects of forces on an object and
determine the relationship between the net force acting on an object and its
acceleration due to this force.
Key questions for this module
This module aims to address the following misconceptions related to force and
motion:
1. If an object stays at rest, there is no force acting upon it.
2. An object continues to move at constant velocity because a constant
force acts on it.
3. If the speed of an object increases, its acceleration also increases.
4. Objects move because they have a force; they stop when their force is
already used up. (Force is thought to be a property of a material)
Do forces always result in motion?
What are the conditions for an object to stay at rest, to keep moving at
constant velocity, or to move with increasing velocity?
How is force related to acceleration?
Unit 1
MODULE
1

6
Start the module by eliciting students’ prior knowledge of force and motion.
Questions such as the following may be asked:
 What makes objects move the way they do?
 Why do objects move in different ways? Why are some objects faster
than the others?
 What makes objects stay in place?
Note that there are no correct or wrong answers yet at this point. Just take note of
their answers and go back to some of them after they finish the module.
Balanced and Unbalanced Forces
1. To introduce the concept of FORCE, place a ball or any object on top of a table
and ask:
a) Will this object move by itself?
b) How can we make this object move?
c) While it is moving, how can we make the object speed up or slow down?
d) How can make it stop?
e) How can we make it change its direction?
Ask students to describe or demonstrate how they can achieve the given
conditions above. This will lead them to realize that to make the object move,
speed up, slow down, stop, or change its direction, it has to be pushed or pulled.
The motion of an object can be changed if we apply FORCE on it
2. Pose another question: Consider again this ball here on top of the table. Since
this ball stays at rest (meaning it does not change its motion) can we say that
there is/are no force/s acting on it?

7
 In this activity, students are asked to identify the forces acting on objects at rest.
This is a very simple activity and the materials are readily available, so students
can work on it individually or in pairs. This is to ensure that everybody is
participating during the activity proper.
 At this point, students need not to explain why the objects stay in place. They
may explain this after they finish doing Activity 2.
 During the post activity discussion, students can be asked to recall what they
learned in the previous grades about the force of gravity. They may be asked to
show or cite examples that demonstrate the presence of the force of gravity on
Earth. If there is enough time, discuss more about gravitational force. Emphasis
should be given on the following ideas:
- Gravitational force is the attraction between any two bodies with mass.
- Gravitational force increases with mass. If the mass of either object
increases, the gravitational force between them also increases.
- As the Earth attracts objects around it, these objects also attract the Earth.
But the Earth is much more massive than them that is why their attraction is
not as great as the gravitational pull of the Earth.
- All things on Earth fall (or are attracted) towards the center of the Earth.
Forces on objects at rest
Activity
1

8
Answers to Questions
Situation 1: Hanging pen
Q1. The pen is at rest.
Q2. Yes. The forces acting on the pen are the
tension force (the force exerted by the string
on the pen) and the force of gravity.
Q3. When the string was cut, the pen falls to the
ground. The force of gravity makes the
object fall down.
Situation 2: Book on a table
Q4. The book is at rest.
Q5. Yes. The forces acting on the book are
the force exerted by the table on the
book and the force of gravity.
Q6. No, the book stays at rest. The book
may be moved by pushing it on one side
only.
The aim of this activity is to help the students understand how the forces
acting on the objects in Activity 1 prevent them from moving.
 In case the number of spring balance is not enough, each group can work on the
first part of the activity first using two spring balances. Then they can be asked to
Balance of forces
Activity
2
Hanging pen
Tension
force
Force of
gravity
Book on a table
Normal force / Force
exerted by the table
on the book
Force of
gravity

9
join with another group to complete the 4 spring balances needed for the four
holes around the board.
 During the post activity discussion, the students must realize that there are still
forces acting upon objects at rest. But these forces balance each other thereby
causing the objects to stay in place. Emphasize the following ideas:
- If two forces acting on an object are equal in magnitude but opposite in
direction, they are considered as balanced forces. These forces must lie
along the same line.
- If the forces acting on an object are balanced, the object either stays at rest
or continues to move at constant velocity.
- If the forces acting on an object are unbalanced, the motion of the object will
change. This concept was discussed in the module using the rolling ball as
an example. Emphasize that the ball slowed down and eventually stopped
not because its force was already used up nor the force acting on it was
continuously decreasing (misconceptions). The ball slowed down and
stopped because an unbalanced force caused it to change its motion. That
unbalanced force is friction. This can be reiterated when Newton’s First Law
of Motion is discussed.
Q7. The forces are equal in magnitude but opposite in direction.
Q8. If the lines of action of the forces are extended, they meet at a single point.
Note: At this point, the term “concurrent forces” may be introduced. When the lines
of action of the forces acting on an object meet at a single point, they are
considered as concurrent forces. When the forces acting on an object are
concurrent, the object does not move nor rotate.
Concept check:
1. Fnet = 20 units
2. Fnet = 5 units. The object will move in the direction of the 10-unit force (larger
force).
3. Fnet = 0. The object will not move.

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Newton’s Three Laws of Motion
 If needed, introduce first Isaac Newton to the class. Discuss briefly some of
his significant contributions especially in the field of physics. e.g. Newton
combined his idea and the ideas of the other scientists like Galileo to give us
a more unified picture of how our universe works. He formulated the laws of
motion and gravitation. Through his three laws of motion, we can describe
and predict the movement of everything around us.
This activity demonstrates how the inertia of an object affects its motion.
Inertia is the tendency of the body to resist changes in its state of motion. This is
described through Newton’s First Law of Motion, also referred to as Law of Inertia.
Teaching Tips
 After discussing the result of the activity, relate the Law of Inertia to the
previous discussion on balanced and unbalanced forces. Emphasize that if
an object is acted upon by balanced forces, its motion or its velocity will not
change. Since acceleration is defined as the change in velocity over time,
then we can say that the object will not accelerate. It will only accelerate if the
forces acting on it are unbalanced. This is what the Law of Inertia is all about.
It states that, “An object will stay at rest or move at constant velocity unless
an unbalanced external force acts on it.”
 If time permits, discuss also the effect of mass on inertia: the greater the
body’s mass, the greater will be its inertia.
 For the application part, relate the concept of inertia to students’ experiences
while riding a vehicle. Then discuss the importance of using a seatbelt.
Coin Drop
Q9. When we slowly pulled the cardboard, the coin on top moved with the
cardboard.
Investigating inertia
Activity
3

11
The frictional force acting between the coin and the cardboard caused the
coin to stay on top of the cardboard and move with it.
Q10. When the coin was flipped quickly, the cardboard moved forward but the coin
did not move with it. When the cardboard was removed from underneath it,
the coin dropped into the glass.
The coin did not move forward with the coin because of the tendency of the
coin to stay at rest (inertia).
Stack of Coins
Q11. When we hit the bottom coin with the edge of the ruler, it moved out from the
pile of coins but the other coins stayed in place. The inertia of the coins has
caused them not to move out with the coin that was hit by the ruler.
In this activity, students will describe the relationship between the unbalanced
external force acting on an object and its acceleration by analyzing tape charts.
 If the materials are available, try to demonstrate how the data or tape charts
were obtained. Hang four identical rubber bands from one end of a wooden
bar as shown in Fig. 1. Then mark on the wooden bar the position where the
rubber bands should be stretched (Fig. 2). When the rubber band is
stretched, it pulls with it the cart. Make sure that the person holding the
wooden board with rubber bands is free to move and ready to run, if needed
to maintain the length by which the rubber band is stretched while pulling the
cart. This is to ensure that the force acting on the cart is constant. The
number of rubber bands used to pull the cart is related to the amount of force
acting on the cart. If the number of rubber bands is changed, say doubled,
the force acting on the cart is considered also to be doubled.
Force and acceleration
Activity
4
Figure 1
Figure 2

12
 Since they do not need to perform the activity, students can be asked to work on
the tape charts (Figure 3) individually or in pairs. Note that their measurements
may differ even if they are provided with the same copies of the tape charts. This
is why they are asked to compute for the acceleration of the cart at least three
times using different values of average velocity. Then they will just get the
average.
 Relate Newton’s Second Law of Motion, also called Law of Acceleration, to the
previously discussed topics, particularly on the effects of unbalanced forces on
the motion of objects.
 Since the law of acceleration quantifies the relationship among mass, force, and
acceleration, it is but necessary to discuss also the effect of mass of the object
on its acceleration. As the mass of the object increases, with the same amount of
force applied, its acceleration also increases. To state in another way, if the
same force acts on two bodies of different masses, the acceleration of the body
with lesser mass is greater than the acceleration of the body with greater mass.
Tape chart analysis
Q12. We noticed that the lengths of the strips in all the tape charts are in
increasing order.
In terms of the difference, we noticed that the amount of change in length of
the strips differs among the tape charts. It is greatest in F=4 units.
Q13. The increase in lengths of the strips suggests that the average velocity of the
cart at equal time interval increases.
The cart is accelerating.
This is also true to all other tape charts.
Q14. The increase in length of each strip from one strip to another is of equal size.
This indicates equal changes in the velocity of the cart at equal periods of
time when the force acting on it is constant.
Yes, this is also true with the other tape charts.
Q15. The increase in length of the strips varies among the four tape charts. The
amount of change increases as the units of force increases.
The increase in length is greatest in F = 4 units and least in F = 1 unit.
Q16. When the dots on top of the strips are connected, a straight line was formed.
Yes, the same pattern exists for the other tape charts.

13
Quantitative analysis
Q17. The computed values of vave are increasing. The cart is accelerating.
Q18. The computed values of ∆v are equal (or almost equal or very close).
This means that the cart is accelerating uniformly or its acceleration is
constant.
Q19. The computed values of acceleration are equal (or almost equal).
Q20. The acceleration of the cart increases with the net or unbalanced force
applied on it. Or as the amount of force applied on the cart increases, the
acceleration of the cart also increases.
The Newton's third law of motion, or sometimes called as Law of Action-
Reaction, describes the relationship between the forces that two bodies exert on
each other. In this activity, students should realize that these forces are equal in
magnitude but opposite in direction.
 Make clear the difference between this pair of forces and the previously
discussed balanced forces. Emphasize that this pair of forces are acting on
different bodies, so they do not cancel each other out.
Q21. (answer may differ, but the values should be equal)
These values represent the amount of pulling force that we exerted on each
other.
Q22. The forces that we exerted are in opposite directions.
Q23. (The readings this time should be greater than the previous ones)
Q24. We increased the force that we exerted on each other.
Q25. (readings may vary)
Q26. The forces are of opposite directions.
Action-reaction
Activity
5

14
F= 2 unitsF=1 unit F= 3 units F= 4 units
Figure 3: Tape charts

15
Solutions:
For F = 1 unit
V1 = 2.5cm/0.10s = 25 cm/s
V2 = 3.0cm/0.10s = 30cm/s
V3 = 3.5cm/0.10s = 35cm/s
V4 = 4.0cm/0.10s = 40cm/s
V5= 4.5cm/0.10s = 45cm/s
Solving for a
2
12
1
50cm/s
0.10s
cm/s230cm/s
t
vv
a 




5
2
23
2
50cm/s
0.10s
cm/s335cm/s
t
vv
a 




0
2
ave
50cm/sa 
For F = 2 units
V1 = 4.5cm/0.10s = 45 cm/s
V2 = 5.5cm/0.10s = 55cm/s
V3 = 6.5cm/0.10s = 65cm/s
V4 = 7.5cm/0.10s = 75cm/s
V5= 8.5cm/0.10s = 85cm/s
Solving for a
2
12
1
100cm/s
0.10s
45cm/s55cm/s
t
vv
a 




2
23
2
100cm/s
0.10s
55cm/s65cm/s
t
vv
a 




2
ave
100cm/sa 
For F = 3 units
V1 = 8.5cm/0.10s = 85 cm/s
V2 = 10cm/0.10s = 100cm/s
V3 = 11.5cm/0.10s = 115cm/s
V4 = 13cm/0.10s = 130cm/s
V5= 14.5cm/0.10s = 145cm/s
Solving for a
2150cm/s
0.10s
85cm/s100cm/s
t
vv
a 12
1





2
23
2
150cm/s
0.10s
100cm/s115cm/s
t
vv
a 




2
ave 150cm/sa 
For F = 4 units
V1 = 14.5cm/0.10s = 145 cm/s
V2 = 16.5cm/0.10s = 165cm/s
V3 = 18.5cm/0.10s = 185cm/s
V4 = 20.5cm/0.10s = 205cm/s
V5= 22.5cm/0.10s = 225cm/s
Solving for a
2
12
1
200cm/s
0.10s
145cm/s165cm/s
t
vv
a 




2
23
2
200cm/s
0.10s
165cm/s185cm/s
t
vv
a 




2
ave
200cm/sa 

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Data for Table 1
Force # of rubber bands Acceleration
F = 1 unit 1 50 m/s2
F = 2 units 2 100 m/s2
F = 3 units 3 150 m/s2
F = 4 units 4 200 m/s2
References
UP NISMED. (2002). Practical Work on High School Physics: Sourcebook for
Teachers. UP NISMED. Quezon City
Acceleration
1 2 3 4
50
100
0
150
0
200
0
Force
Figure 4: Graph of force vs acceleration

17
WORK AND ENERGY
In this module, students will learn about motion from the perspective of work
and energy. The concept of energy is one of the most important concepts in physics.
The students have been studying about it since Grade 3 up to Grade 7. They have
learned that energy takes many forms; there are different sources and uses of
energy; and energy can be transferred.
The module starts with a discussion about work. In the first activity, they will
explain whether a situation represents an example of work. It is followed by a
discussion about work and energy, and then about kinetic and potential energy. In
the second activity, students will construct a toy that demonstrates how a rubber
band ‘stores’ energy. The last activity puts together the concepts of work, energy and
power.
What is work?
Figures 1 to 3 in the student’s module shows different situations. Ask the
students to identify the one doing the work and on which object the work is done.
The students should be able to arrive at the concept that work is done on an
object when the force applied to it covers a distance in the direction of the applied
force.
What is work?
What is energy?
How are work, energy and power related?
Unit 1
MODULE
2

18
In this activity, students will analyze the situations shown in the illustrations.
For them to explain if the situations represent examples of work they should be able
to identify the one doing the work and on which object the work is done. They should
also look into the direction of force exerted relative to the direction of the movement
of the object or the distance covered by the applied force.
Teaching Tips
1. Ask the students what’s the first thing that comes to their mind when they
hear the word work.
2. Let them look for the meaning of work in a dictionary.
3. Recall the lesson about force in Module 1.
 A girl is pulling her toy car.
Yes, the situation is an example of work. The work is done by the girl on the
cart. The force exerted by the girl in pulling the toy car is in the same direction
as the distance covered when the force is applied.
 A man is lifting a box to be placed on a table.
Yes, the situation is an example of work. The work is done by the man on the
box. The force exerted by the man is upward and the box is displaced
upward.
 A girl carrying a bag walks down the street.
No, the situation is not an example of work. There is force (the shoulder
pushes up the bag) and there is displacement (the bag is moved
horizontally). However, the line of action of the force and the displacement
are not parallel but perpendicular. The distance covered is not along the
direction of the applied force.
Is there work done?
Activity
1

19
 A mango fruit falling from the branch
Yes, the situation is an example of work. The work is done by the force of
gravity on the mango. In this case, the mango loses energy as you will find
out in the discussion of potential energy.
Calculating work
The students are given the equation of work in their module. However, the
equation can only be used if the force is applied horizontally (pushed across the floor
or ground) or vertically (lifted above).
Figure 1. Equation for solving work
The equation of work for forces at an angle is not introduced to the students
because they have not yet taken up trigonometric functions in their mathematics
class. However, if the students ask how to solve for work if the force is at an angle,
you may also show the equation.
Figure 2. Equation for solving work if the force is at an angle
d
force
d
force
force

20
Answer to the problem:
A book which has a mass of 1 kg is on the floor. If the book is lifted from the
floor to the top shelf which is 2 meters from the floor, how much work is done?
Work is a Method of Transferring Energy
 In Grade 7, students learned that there are different ways by which energy can
be transferred from one place to another. This time, they will learn that work is a
means of transferring energy from one object to another.
 Is there work done on the ball? In the bowling game described in the student’s
material, the work is done by the person on the ball to just start it moving.
Because of the work done to the ball, it gained ‘something’ that enables it to
move. That ‘something’ that was transferred to the ball is called energy. The
energy became energy of motion of the ball.
 What can a moving ball do? A moving ball has energy. When it strikes the empty
plastic bottle, it can push it through a distance. Thus, work is done by the ball on
the empty plastic bottle. Since work is done on the bottle, energy is transferred to
it.
 If energy can be transferred, what happens to the energy of the one doing the
work and to the object on which work is done? The one doing the work loses
energy and the object on which work is done gains energy. When work is done
by an object, the object loses energy; when work is done on an object, the object
gains energy. In the bowling game the students played, the one rolling the ball
loses energy while the ball gains energy. When the moving ball strikes the empty
plastic bottle it loses energy while the plastic bottle gains energy.

21
 Clarify to the students that it is energy and not force that is transferred when
work is done.
 You may also show or demonstrate a billiard game wherein one ball hits another
ball.
Kinetic Energy
 The energy of a moving object is called energy of motion or kinetic energy (KE).
How the equation of KE is derived is shown in the student’s module.
 The KE of an object depends on its mass and velocity. What will happen to the
KE of an object if its mass is doubled but the velocity remains the same? The KE
will be doubled. How about if the velocity is doubled but the mass remains the
same? The KE is proportional to the square of the speed, thus if the speed is
doubled, the KE will be quadrupled.
A 1000 kg car has a velocity of 17 m/s. What is the car’s kinetic energy?
Potential Energy
Work is done in lifting an object. When work is done on an object, energy is
transferred to it. Thus, an object lifted from the ground gains energy. Since the work
is done against the force of gravity, it is called gravitational potential energy or simply
potential energy (PE).
The force of gravity also acts on objects falling to the ground. As an object
falls, the potential energy decreases because it is transformed to become the kinetic
energy of the object.

22
The gravitational potential energy is the energy due to its position. This
energy depends on the mass and height of the object. The height can be measured
relative to an assigned level. But usually, the common reference level is the ground.
Teaching Tips
1. Point out that the higher the object is from the ground, the greater is its potential
energy. The more massive an object is, the greater is its potential energy. These
concepts were demonstrated in the problems.
2. Compare the potential energy of an object/s for different reference level.
If the same 1.0 kg book is lifted 0.5 m above the table, but the table top is 1.0 m
above the floor, what would be the potential energy of the book if the reference level
were the floor?

23
 Prepare a sample toy made of a can instead of the transparent plastic
container. This way the students cannot see the mechanism inside the can.
Rotate the barbecue stick beforehand before asking them what they think will
happen to the can when placed on the floor.
 After the activity, ask the students to demonstrate the game they played
using a rubber band. Ask them how the rubber bands ‘store’ energy and what
this energy can do once transformed to kinetic energy.
Answers to the questions:
Q1. It rolls.
Q2. Potential energy
Q3. Kinetic energy
Q4. Potential to kinetic energy
Work, Energy and Power
People possess energy. They get their energy from the food they eat. As
shown and demonstrated in the previous lesson, this energy can be transferred to
objects.
When people do things such as walking or running, they expend energy. The
rate at which they expend energy is called power. Power is the rate of doing work or
the rate of using energy.
Rolling toy
Activity
2

24
In this activity, the students will relate the concepts of work and energy to
power. The energy expended in climbing a flight of stairs is equal to the gravitational
potential energy, PE = mgh or weight x height.
Sample data for Table 1
Name Weight (N)
Height of
stairs (m)
Time taken to climb
the stairs (s)
Energy
expended (J)
Power
(J/s)
Bella 441 5 10 2205 220
Troy 490 5 8 2450 306
Mae 392 5 10 1960 196
Elijah 441 5 9 2205 245
Answers to the questions (based on the sample data for Table 1):
Q5. Troy
Q6.
Q7. Mae
Q8.
How POWER-ful am I?
Activity
3

25
Q9. Each member performed different amounts of work except for Bella and
Elijah who performed the same amount of work because they weigh the
same.
Q10. Power output is determined by the amount of work done or energy expended
and the time taken to do the work.
Summary
Below is a list of concepts or ideas developed in this module.
 Work is done on an object when the force applied to it covers a distance
in the direction of the applied force.
 Work is a way of transferring energy.
 When work is done by an object it loses energy and when work is done
on an object it gains energy.
 The energy of an object enables it to do work.
 A moving object has energy called energy of motion or kinetic energy.
 An object above a specified level has energy due to its position called
potential energy.
 An elastic object that is stretched or compressed or twisted has energy
called potential energy.
 Power is the rate of doing work or the rate of using energy.

26
References
Henderson, Tom. (21 January 2013). Retrieved from
http://www.physicsclassroom.com/class/energy/
Hewitt, P.G. (2002). Conceptual physics. USA: Prentice-Hall, Inc. Saddle River, New
Jersey.
Kirkpatrick, L.D. and Wheeler, G.F. (1998). Physics a world view. USA: Saunders
College Publishing
Ostdiek, V.J. and Bord, D.J. (1987). Inquiry into Physics. USA: West Publishing
Company
DepEd. Science and Technology IV. SEDP Series. (1992). Philippines: Book Media
Press, Inc.

27
HEAT AND TEMPERATURE
In Grade 7, students learned about the conditions necessary for heat transfer
to occur and the ways by which heat transfers from one place to another. This time,
they will explore what happens to the object when heat is transferred to or from it.
They will also learn about the factors that affect the amount of heat that an object
can transfer. Students are also expected to understand the difference between heat
and temperature. Furthermore, this module hopes to address the following
misconceptions on heat and temperature:
1. Heat is a substance.
2. Heat is not energy.
3. Heat and temperature are one and the same.
4. The temperature of an object depends on its size or volume.
5. The amount of heat transferred is determined always by the change in
temperature.
Notes:
 This module is good for 6 days. The experiments were made simple so that
students will be able to finish them early and the discussion of the results can
be done also on the same day.
What happens to solids, liquids, or gases when they absorb or
release heat?
Does heat affect all kinds of materials in the same way?
Are heat and temperature one and the same?
Unit 1
MODULE
3

28
 The word heat in the module is written in italic form to emphasize that it
represents the quantity of thermal energy that is transferred to or from an
object.
 Since the students will be using a laboratory thermometer in all the
experiments, it is advised that the guides on how to use the device properly
are discussed at the beginning of the chapter.
 In this activity, students will describe the hotness or coldness of water in
terms of its temperature. They will also compare the amount of heat
transferred to the water in terms of the changes in its temperature and
describe the relationship between these two variables.
 The first part of the activity requires the students to recall their previous
lesson on heat transfer. Since this is just a review of their previous lessons,
students may be allowed to discuss their answers within their group. Make
sure that the following concepts are made clear among the students:
 Heat is a transfer of (thermal) energy between objects or places due
to temperature difference.
 Heat transfers from an object of higher temperature to an object of
lower temperature.
 When determining the hotness or coldness of the water, make sure that
students use different fingers for each water sample.
Sample Data
Container
Temperature Change in
temperatureInitial Final
Container 1 12°C 56°C 44C°
Explaining hotness or coldness
Activity
1

29
Q1. Heat was transferred from my finger (higher temperature) to the cold water
(lower temperature).
Q2. The water was cold. The energy was released from my hand to the water.
Q3. (Answers may vary, depending on how close the students’ answers are to
the measured value)
Q4. Container 1 or the container that was added with hot water
Container 3 or the container that was added with cold water
Q5. The water added to the containers are of different temperatures.
Q6. Heat transfer was taking place in containers 1 and 2. There was a change in
the temperature of water in these containers.
Q7. Greater amount of heat was transferred in container 1. There was greater
change in the temperature of water.
Q8. The amount of heat transferred is proportional to the change in temperature.
The greater the amount of heat transferred to an object, the greater the
increase in its temperature.
The aim of this activity is to explain why the temperature of water in Activity 1
increases when heat was added to it. Also, by observing the behavior of the dye
through the water, students will describe the effect of heat transferred to the particles
of water.
The greater the amount of heat transferred to an object, the greater the
increase in the kinetic energy of the particles and the greater the increase in the
temperature of the object.
Teaching Tips
1. At this point, students should be made to realize that everything is made up
of moving particles.
Dye in water
Activity
2

30
2. In Table 2, last column, students’ observations must focus on the scattering
of the dye through the water. Ask them to make comparisons, like the dye
scatters faster (or slower) or the dye scatters the most (or the least). They will
later relate these observations to the speed of the moving particles.
3. At the end of the discussion, students should be able to recognize that
“hotness or coldness” indicates how fast the particles move. “Hot” may be
considered as faster movement of the particles or higher kinetic energy of the
particles.
Sample data for Table 2:
Container
Temperature
(0
C)
Observations
Container 1 (cold) 12 0
C Dye scattered the slowest
Container 2 (tap) 26 0
C
Dye scattered slower than in
hot water or faster than in
cold water
Container 3 (hot) 76 0
C
The dye scattered the fastest
in this container
Figure 1. Scattering of the dye among the three water samples
Q9. After putting drops of dye into the water, the dye scattered throughout the
water. The rate of scattering of the dye differs in each container.
Q10. Hot water. Cold water.
Cold waterWater at
room temp
Hot water

31
Q11. The higher the temperature of the water, the faster the scattering of the dye.
Q12. The particles are moving fastest in the container with hot water. The particles
are moving slowest in the container with cold water.
Q13. The higher the temperature of the water, the greater the speed of the moving
particles.
Q14. The higher the temperature, the greater the kinetic energy of the particles.
Thermal Expansion
 Explain how liquid thermometers work using the concept of thermal
expansion.
 Demonstrate the activity described or suggested in the module to explain
thermal expansion of solid.
 Emphasize that objects or materials expand when heated and contract when
cooled. But emphasize also that different materials expand or contract to
different extents when heated or cooled.
 If time permits, ask the students to research more on the applications of
thermal expansion to real life.
Phase Change
Teaching Tips
1. If the materials are available, some groups or students may be allowed to use a
burner to heat the beaker of ice. Then let them compare their results and
explain the difference in terms of the effect of the amount of heat absorbed by
the ice to the time the ice takes to melt completely.
What happens when ice melts?
Activity
3.1

32
2. Students can be allowed to use an iron stand with clamp to hold the
thermometer to ensure that it will not touch the bottom of the container.
3. At this point, some guides in constructing graphs might be needed. Note that
the independent variable (heating time) is plotted along the horizontal axis
while the dependent variable (temperature) is plotted along the Y-axis.
4. Try out the activity first to determine the amount of ice that will allow the
students to finish their activity on time.
Q15. The ice melts because the heat from the surrounding (higher temperature)
was absorbed by the ice (lower temperature).
Q16. The dependent variable is the ‘temperature’ while the independent variable is
the ‘time’.
Q17. Descriptions may vary depending on how the graphs of the students look like.
The accepted one should have a straight horizontal line like in the graph
shown in Figure 2 below (melting).
Q18. The temperature of the water while the ice was melting remains the same.
Q19. After the ice has melted the temperature of the water increases with time.
Figure 2
Melting
Vaporization
Temperature
Time
Heat
100°C
(Boiling point)
0°C
(Melting point) Ice
Water
Steam
(vapor)

33
Q20. Descriptions may vary depending on how the graphs of the students look like.
The accepted one must have a straight horizontal line like in Fig. 2
(vaporization).
Q21. Both graphs have a straight horizontal line but the temperature level
corresponding to these lines differ.
After students learned about the relationship between the temperature of the
object and the amount of heat it can transfer, this time they will try to investigate on
their own the relationship between the mass of the object and the amount heat it can
transfer. In this activity, students are asked to plan and design their own
investigation, including the steps on how they will gather and analyze data to come
up with an answer to this question: How does the mass of an object affect the
amount of heat it can transfer?
Example:
Students may fill identical containers with different amounts of water of the
same temperature, say hot water. Then they pour both contents into two
containers with water of the same amount and temperature. Then they
measure the increase in temperature of water in both containers. The amount
of increase in the temperature of water can be related to the amount of heat
transferred to the object.
What is the relationship between the
mass of a material and the amount of
heat it can transfer?
Activity
4
What happens to the
temperature of water as it boils?
Activity
3.2

34
Teaching Tips
1. Make sure that the liquid samples are stored in the same room before the
experiment to ensure that they will be of the same room temperature when
they are used in the activity.
2. Aside from water and cooking oil, other samples of liquids can also be used.
3. If there are enough thermometers available, it is better to use a separate
thermometer for each liquid sample.
4. During the post activity discussion, provide the class with the table containing
the specific heat capacities of some materials. This will confirm their findings
that different materials have different heat capacities.
5. During the post lab discussion, include some real life applications of specific
heat capacity.
Q22. The water requires more time to increase in temperature.
Q23. The water requires more heat to increase in temperature.
Q24. The water has greater heat capacity.
Link
http://www.biol.wwu.edu/donovan/SciEd491/HeatTempUnit.pdf
Comparing heat capacities
Activity
5

35
How do voltage and resistance affect electric current?
What are the safety precautions needed in using electricity?
ELECTRICITY
In the previous modules, students learn about charges and how their charges
determine the forces that exist between them. In this module, they will study charges
as moving through conducting materials. Students will be dealing mostly on terms
like voltage, current and resistance in studying electricity. In the first activity, they will
determine how changing the voltage affects the current in an electric circuit. The
second activity deals with how resistance affects the current in a circuit. The next
activity talks about the two types of connection (series and parallel connections) and
how the charges flow in these connections. The last activity of this module deals with
the effects of too much current in the circuit on conducting materials, and how its
effect can be useful in practicing safety practices in using electrical appliances in
order to prevent accidents like fires or electric shock.
The topics covered in this module are relevant because of the applicability of
the lesson in preventing accidents like fires caused by unsafe use of electricity.
Unit 1
MODULE
4

36
Current and Voltage
Electric charges can be made to move through a conducting material. The
electric charges are the electrons of the conducting materials. Materials such as
copper, steel, and aluminum have a lot of loosely held electrons which made them
good conductors of electricity. Current is a measure of the number of charges
passing through a cross-section of a conductor in a given time.
What is the direction of current? A battery has terminal marks “+”and “-“. The
plus (+) sign indicates surplus or excess of charge and the negative (-) sign means
deficiency. The movement of charges from the positive side of the battery to the
negative side is called conventional current or simply current. However, this is not
the actual motion of electrons in a circuit. The direction of the flow of electrons is
from the negative terminal to the positive terminal. This is called electron current.
The direction of current does not affect what the current does.
An ammeter measures electric current. Because the device measures how
much charges flow in a certain cross section at a given time, it has to be connected
in series. Take note how the positive and negative signs of the ammeter and the
terminals of the battery are oriented as shown in Figure 1.
Figure 1. Ammeter connected in a circuit
Energy is needed to make the charges move. In Module 2, the students
learned that when work is done on an object, energy is transferred. The voltage of a
battery does the work on charges to make them move. Batteries are energy sources.
The chemical energy in the battery is transformed to electrical energy. This electrical
energy moves the charges in a circuit. The work done on the charges as it passes
through a load is measured as the voltage across the load.

37
A voltmeter measures voltage. The voltmeter must be connected parallel or
across the load as shown in Figure 2. The positive terminal of a voltmeter is
connected to the positive terminal of the bulb while the negative terminal is
connected to the negative terminal of the bulb as shown in Figure 2.
Figure 2. Voltmeter connected across the load
 In this activity, students will determine how voltage and current are related.
 Students will use voltmeters and ammeters to measure the current and
voltage in a circuit. Make sure that they follow the correct way of connecting
the ammeter and voltmeter. If the school cannot provide voltmeters and
ammeters, they can modify the activity by just relating the number of dry
cellsor increase in voltage with the brightness of the bulb. The brighter the
bulb, the bigger the current.
 The dry cells must be connected in series which means the positive terminal
of one cell is connected to the negative terminal of the other.
 Ideally a switch must be included in the circuit so that they can turn off the
circuit to avoid wasting energy. The teacher can make an improvised switch
using illustration board and aluminum foil as shown in Figure 3.
Current and voltage
Activity
1
positive terminal
of the bulb
negative terminal
of the bulb

38
Figure 3. An improvised switch
 Be sure also to use new batteries for this activity especially when the
brightness of the bulb is being asked. For the bulb, use a flashlight with a
voltage rating of 2.5 V.
 In case no battery holders, use a cardboard to wrap two batteries tightly like a
cylindrical holder. Tape the cartolina to secure the tightness of the connection
of the batteries.
Answers to Questions:
Q1. (This will depend on the reading they get from the ammeter.)
Q2. The bulb glows brighter when two batteries are used.
Q3. (This will depend on the reading obtained in the ammeter.)
Q4. The current is higher for two dry cells as compared to one dry cell.
Q5. (This will depend on the readings obtained on the voltmeter.)
Q6. The bulb glows brighter.
Q7. This will depend on the readings obtained on the voltmeter.)
Q8. The voltage is bigger for two dry cells as compared to one dry cell.
Q9. For a constant load (one bulb), when the voltage increases the
current also increases.

39
Sample Data
No. of batteries Voltage (V) Current (A)
1 1.5 0.2 A
2 2.5 0.3 A
Activity 1 Discussion
The dry cell provides the energy that moves the charges in a circuit. The
dry cell must be connected by conducting wires to a load to form a complete circuit.
Adding dry cells in series increases the voltage in a circuit.
In the activity, adding dry cells increases the current in a circuit as shown by
the ammeter readings. The brightness of the bulb also indicates the amount of
current passing through it. The bigger the current through the bulb, the brighter it
glows. Both the meter readings and the brightness of the bulb show that voltage and
current are related. The activity shows that as the voltage increases, the current
also increases.
Current and Resistance
Another variable that can affect current is the resistance. As the term implies,
the resistance of the material opposes the flow of charges. Resistance can also be
measured and they are expressed in units called Ohms. A lower resistance would
mean that there is less opposition in the flow of charges and therefore bigger current.
Different materials have different amounts of resistance. Conductors
definitely have very little resistance and therefore allow more charges to pass
through. Insulators are materials that have very high resistance and therefore flow of
charges would be difficult.
The length and thickness of the conducting wire are factors that affect
resistance encountered by current. The longer the wire the greater will be its
resistance and the greater the cross sectional area (a measure of the thickness of
the wire), the lower will be its resistance.

40
The resistance of an object also changes when the object becomes wet. Dry
human skin for instance has a resistance of 100,000 ohms but when it gets wet its
resistance is reduced to 1,000 ohms. That is why it is important to dry the hands
when plugging an electrical appliance to reduce any chance of getting a lot of current
if an accident occurs.
Understanding the relationship between current and resistance is important in
protecting oneself from electric shock. The table below shows the physiological
effects that happen when a certain amount of current passes through the human
body.
Source: Department of Health and Human Services, Center for Disease Control and
National Institute for Occupational Safety and Health
In this activity, the students must be able to determine how resistance
affects the current through the circuit.
Current and resistance
Activity
2

41
 The purpose of the activity is to find if a relationship exists between current
and resistance.
 If there is no ammeter available, the students can just compare the
brightness of the bulb since the brightness is also associated with the current
passing through them.
 In the last part of the activity, the students were asked to connect the
ammeter at different points in the circuit. This is to show to them that current
is the same anywhere in the circuit.
Answers to Question
Q10. The current decreases as the resistance increases or when the resistance
increases the current decreases.
Sample data:
Q11. The current reading at different points of the circuit is constant.
Q12. The readings indicate that current is the same anywhere in the circuit.
Electrical Connections
Series Connection
Circuit A in Activity 3 is a series circuit. In a series circuit, loads form a single
pathway for charges to flow. A gap or a break anywhere in the path stops the flow of
charges. When one bulb is removed from the socket, a gap is created. The other
bulb turns off as there is no longer current in the circuit.
No. of bulbs Current (A)
1 0.3 A
2 0.25 A
3 0.2 A

42
The total resistance in a series circuit is equal to the sum of the individual
resistances of the load (bulb). Current is the same in every part of the circuit. The
current is equal to the voltage divided by the total resistance. As more load (bulb) is
added in a series circuit, the smaller the current as reflected by the brightness of the
bulb. The voltage across each load depends on the load’s resistance. The sum of
the voltage across each load is equal to the total voltage.
Parallel connection
Circuit B in Activity 3 is a parallel circuit. In a parallel circuit, loads form
branches; each provides a separate path for charges to flow. A gap or a break in any
branch will not affect the other branches. Thus, when one bulb is removed from the
socket, a gap is created only for that branch. The other bulbs still glow as their path
is still complete.
In a parallel connection the voltage is the same across each load. The total
current is equal to the sum of the currents in the branches. The amount of current is
inversely proportional to the resistance of the load.
 In this activity students will find out how series and parallel connections are
constructed. Giving them a situation to figure out how to do it stimulates
problem solving skills of students.
 Be sure that when you let them do circuit A there should only be three wires
for each group. For circuit B only four wires should be given. If the number of
wires is not limited, they will not be able to execute the simplest way to
demonstrate connections of bulbs in series and parallel.
 Tell the class to show them what they have constructed and check if it fits to
the condition (one bulb unscrewed, then other one turns off for Circuit A; one
bulb is unscrewed and the other bulb remains lighted for Circuit B). Usually
the series connection is easier for the students. For parallel connections,
students will experience some challenge in doing it.
 Most textbooks show parallel connections shown in Figure 6:
What’s the connection?
Activity
3

43
Figure 4 A parallel circuit
However, students might have another way of connecting the bulbs and
these possible outputs shown below are also in parallel.
Figure 5 Parallel circuits
 In the last part of the activity, the students were asked to measure the voltage
across the two bulbs and the voltage drop across each bulb in circuits A and
B. Sample data is shown below:
Table 3
Circuit Voltage drop (V) Voltage across the
two bulbs (V)Bulb 1 Bulb 2
A 1.5 1.0 3
B 2.5 2.5 3

44
Circuit A shows that the voltage of the dry cell is divided between the two
bulbs. The voltage depends on the resistance offered by the bulbs. If the bulbs are
identical, the measurement should be the same.
Circuit B shows that the voltage across each bulb is almost equal to the
voltage of the dry cells. This shows that in this type of connection, voltage is the
same across any two points in the circuit.
Q13. There is only one path for current in Circuit A.
Q14. Because there is only one pathway for the current, when one bulb is removed
from the holder, it made a gap or a break in the path. A gap or a break
anywhere in the path stops the flow of charges. All bulbs connected will go
out.
Q15. There are two paths for current in Circuit B.
Q16. Since only the path of the unscrewed bulb has the gap, the other bulb shines
because its path is complete. The current can still pass in the path of the bulb
with a complete pathway.
Q17. Circuit B has brighter bulbs.
Q18. The current in Circuit A becomes smaller as more bulbs are added because
the bulbs glow dimmer. The brightness of the bulbs in Circuit B remains the
same as bulbs are added in the circuit. The current in Circuit B is bigger than
in Circuit A.
Safety in Using Electricity
Fires can happen when the wires start heating up causing combustible parts
of the house to be set on fire. The wires heat up when the current passing is more
than what the wires can carry. In this case there is an overloading of the circuit. An
example of how the circuit gets overloaded is by plugging a lot of appliances in a
common outlet like an extension cord.
Another instance of overloading of the circuit is the presence of short circuits.
Short circuits happen when wires with defective rubber insulation touch each other
so the current does not pass to the supposed path it should take. It is a circuit where
the current encounters very little resistance and therefore the amount of current will
increase rapidly. Such increase in the amount of current leads to the overloading of
the circuit and can lead to fires.

45
But why do wires heat up when there is too much current? In the wires the
electrons that flow in a closed circuit collide with the atoms of the conducting wire. As
the collisions take place the kinetic energy of the metal atoms increases. The
increased kinetic energy of the atoms is dissipated as heat. You learn in the module
on heat that temperature is related to the kinetic energy of the moving particles. The
higher the kinetic energy of the particles, the higher will be its temperature. The
higher the current passing through the wire, the more collisions between the
electrons and the atoms of the wire take place. In the end the wire will become hot.
So just imagine how much heat will be generated from an overloaded circuit.
 There are two tasks in Activity 4. The first part shows how increasing the
current can cause the wires to heat up. The second task shows how a short
circuit happens.
 The fine copper wire to be used can be obtained from stranded electric wires.
Remove the rubber insulation and get these fine copper wires for this activity
Figure 6 Strands of copper wires
 The first task shows the wire heats up melting the candle. The hotter the wire
the deeper will be the cut made on the candle.
Stay safe!
Activity
4

46
 The second task is a simulation of a short circuit. Supervise the students
making sure that they don’t let touching of the exposed parts of the wire take
too long as the wires get hotter afterwards.
Q19. The candle touching the wire melts.
Q20. The current in the circuit increases.
Q21. Heat is produced along the wire. The bigger the current in the circuit, the wire
becomes hotter, and the more the candle will melt.
Q22. The light goes off when the wires touch each other.
Q23. The current took the path of the exposed part of the wire touching each other.
Q24. The resistance encountered in the short circuit where the charges flowed is
lower.
Q25. The current in the short circuit increases.
Q26. Short circuits cause fire when the nearby materials near the wires becomes
so hot and starts to burn.
Q27. Resistance decreases as more appliances are connected to one outlet.
Q28. The total current increases.
Q29. Overloading the circuit can make the wires hot setting combustible materials
on fire.
References and Links
Henderson, Tom. (21 January 2013). Retrieved from
http://www.physicsclassroom.com/class/energy/
Hewitt, P.G. (2002). Conceptual physics. USA: Prentice-Hall, Inc. Saddle River, New
Jersey.
Kirkpatrick, L.D. and Wheeler, G.F. (1998).Physics a world view. USA: Saunders
College Publishing
Ostdiek, V.J.and Bord, D.J. (1987).Inquiry into Physics. USA: West Publishing
Company
DepEd.Science and Technology IV.SEDP Series. (1992). Philippines: Book Media
Press, Inc.
http://www.allaboutcircuits.com/vol_1/chpt_3/4.html

47
SOUNDS
This unit deals with the propagation of sound through solid, liquid, and gas. In
the course of discussion, wave characteristics and properties particularly reflection
and refraction will be taken into account. From the activities, students will be able to
identify also the factors that affect the speed of sound.
At the end of the unit, students should be able to:
1. compare the speed of sound through solids, liquids and gases;
2. infer how the molecular structure of a material affect speed of sound
moving through it; and
3. investigate the effect of temperature on speed of sound through fair
testing
Unit 1
MODULE
5
1. Sounds can be produced without using any material objects.
2. Hitting an object harder changes the pitch of the sound produced.
3. Sounds can travel through empty space (a vacuum).
4. Sounds cannot travel through liquids and solids.
5. Sound travels slower in less dense medium.
6. The greater the density of the medium the faster the sound is
transmitted.
Related Misconceptions

48
WORKSHEET 1: Solids, Liquids, and Gases
Direction: Using several resources and references, compare the different
characteristics of solids, liquids and gases by completing the table below:
Comparing Solids, Liquids, and Gases
Characteristics Solid Liquid Gas
Intermolecular
spacing
very close Slightly farther Far from one
another
Volume Has definite shape Takes the shape
of the container
Takes the shape
of the container
Ability to flow Cannot flow Able to flow Able to flow
Compressibility Not compressible Not compressible Highly
compressible
Density densest dense Low density
On which medium does sound travel fastest? Solid, Liquid, or Gas?
How does the temperature of the medium affect the speed of sound?
How are reflection and refraction manifested in sound?

49
Facilitating Learning
Motivation
 The facilitator may start with the popular songs of popular artists like
maroon 5, Justin Bieber, and Taylor Swift. Students may be asked to sing
some of the popular tunes and ask them who are fun of watching
concerts? Also ask them why concerts are usually done during night time
and not during day time. Probe further until the concept of sound as a
wave is deduced.
 Introduce Activity No. 1 to arrive at the objectives: (1) to infer that sound
waves are vibrations that travel through the air and (2) to infer that sound
is transmitted in air through vibrations of air particles.
 Since Activity No. 1 includes two parts, emphasize the focus of each part
so as to guide the students while on task.
 Data processing may be done by group presentation and class discussion
of the guide questions to probe the concept that sound waves are
vibrations that travel through the air and that sound is transmitted in air
through vibrations of air particles.
 Discussion should also be extended to cover the differences and
similarities of longitudinal and transverse waves and introduction to the
characteristics of longitudinal waves.
 Then introduce Activity No. 2: Characteristics of Waves: Comparing
Longitudinal Waves and Transverse Waves. In this activity the students
will use a metal slinky to (1) distinguish the different characteristics of
waves; (2) determine the frequency and wavelength; and (3) compute the
wave speed based on the frequency and wavelength.
 Data processing may be done by group presentation. Class discussion of
the data in tabular form and guide questions to the characteristics waves.
 Extend the discussion to emphasize that sound waves are also called
pressure waves. From here, introductory discussion on factors affecting
sound may be included.

50
 Then introduce Activity No. 3: Sound Race…Where Does Sound Travel
Fastest?. In this activity the students should be able to distinguish which
material transmits sound the best.
of the data and results in tabular form and guide questions to speed of
sound in different media.
 Extend the discussion to include characteristics of other media like solids
and liquids then let them do worksheet 1 and Activity No. 4:
Chimes...Chimes...Chimes... In this activity, they will have to design their
own chime and use this chime to determine how density of the material or
medium affects the speed of sound.
 Ask where does sound travel faster? In hotter medium or cooler medium?
Introduce Activity No. 5: Faster Sound...In Hotter or Cooler? In this
activity the students will be able to determine how temperature affects the
speed of sound.
 Extend the discussion to include calculation of the speed of sound with
respect to the temperature of the medium. Let them do Worksheet No. 2.
 Summarize Lesson 1 by going back to the key questions particularly
questions 1 and 2.
 Use the question posted in the motivation to introduce the concept of
properties of sound. Then introduce Activity No. 6: Reflecting and
Refracting Sound...
of the data and results in tabular form and guide questions to refraction
and reflection of sound waves.
 Extend the discussion to include practical application of sound reflection
and refraction.
 Summary of the whole module may be probed by asking the 3rd
key
question and by asking for insights and experiences they had during the
preparation, presentation and post-presentation discussion of their
outputs.

51
In this activity, students will be able to infer that sound is KE of vibrations that
travel through the air; and sound is transmitted in air through vibrations of air
particles.
Q1. The salt bounced up and down.
Q2. When the small can is tapped loudly or forcefully.
Q3. Sound was produced when the small can is tapped. Yes the salt bounced
up and down the plastic top while tapping the small can.
Q4. The sound produced in the small can made the plastic top of the large can
vibrate making the salt bounce up and down.
Q5. Sound waves are vibrations of air particles.
Q6. The rock salt bounced higher the loudness of the sound is increased.
Q7. The amplitude of the wave.
Q8. The other colored beads collided with the blue bead.
Q9. Yes
Q10. Yes
Q11. Sound wave is classified as a longitudinal wave.
In this activity, students will be able to distinguish the different characteristics
of waves; determine the frequency and wavelength; and compute the wave speed
based on the frequency and wavelength)
Characteristics of waves: Comparing
longitudinal and transverse waves
Activity
2
The dancing salt and the
moving beads!
Activity
1

52
Q12. frequency
Q13. Wavelength is decreased provided the frequency of shaking or disturbing
the medium is the same or constant.
In this activity, students will be able to distinguish which material transmits sound
the best.
Q14. Yes / Yes/ Yes
Q15. Yes / Yes / Yes
Q16. Wood/Water/Metal/Metal
Q17. The sound seems louder in the string as compared to air.
Q18. Yes
Q19. Yes
In this activity, students will be able to infer using improvised chimes that
closely spaced particles of the medium are best transmitters of sound.
Q20. Chime 2
Q21. Chime 2
Chimes...Chimes...Chimes...
Activity
4
Sound race... Where does
sound travel fastest?
Activity
3

53
Q22. Chime 3
Q23. Chime 3 / Chime 3
Q24. The chime with packed string objects produces sound that reached the
farthest distance.
Q25. Chime 3
Q26. The more closely distanced the stringed objects in the chime, the better the
sound is transmitted.
In this activity, students will be able to be able to determine how temperature
affects the speed of sound.
Q27. HOT cylinder
Q28. HOT cylinder
Q29. HOT cylinder
Q30. HOT cylinder
Q31. The higher the temperature, the faster the sound travels.
In this activity, students will be able to be able to observe how longitudinal
waves reflect and refract.
Reflecting and refracting sound
Activity
6
Faster sound...In hotter or cooler?
Activity
5

54
Q32. The compressions or rarefactions bounce off after hitting the wall
Q33. No they are not found on the same positions
Q34. Sound will also bounce off when it strikes a fixed end or the wall
Q35. The frequency of the wave increases
Q36. Increase in frequency of the sound is manifested as change in pitch
Q37. Amplitude increases
Q38. Louder sound is observed
Q39. Faster waves
References
http://www.hk-phy.org/iq/sound_night/sound_night_e.html
http://www.schoolphysics.co.uk/age11-
14/Sound/text/Refraction_of_sound/index.html

55
COLORS OF LIGHT
This unit is concerned with the demonstration of understanding of the some
properties and characteristics of light. Among the characteristics and properties of
light, we focus on refraction and specifically dispersion of light. We will try to find out
through simple activities on how light disperse to form the colors of light. We will also
try to find the hierarchy of colors of light in terms of frequency, wavelength, and
energy. The different activities provided in this module will make us realize the
beauty of everything with light.
At the end of the unit, students should be able to:
1. demonstrates the existence of the color components of visible light using
a prism or diffraction grating;
2. infers that color is a manifestation of visible light’s frequency or
wavelength;
3. explains that red is bent the least and violet is bent the most according to
their wavelengths or frequency; and
4. explains the hierarchy of colors in relation to energy.
How are refraction and dispersion demonstrated in light?
In the different colors of light, which is bent the most and the least?
Why do we see spectacular events in the sky like rainbows, red sunset and
blue sky?
Unit 1
MODULE
6

56
Refraction of Light
Activity
1
Given:
i = 23o
; r = 14o
; ni = 1.00029
Required to Find: ni
Solution: 
Given:
i = 35o
; ni = 1.33
Required to Find: r
Solution: 

57
Description of Activities
 Activity 2: The Colors of the Rainbow...The Colors of Light..
(The students will be able to infer that white light is made up of many different
colors of light and each of these colors of light bends differently.)
 Activity 3: Red vs. Blue
(Students will be able to infer that Violet light bends more than red light when
dispersed; and Bending depends on the refractive index, frequency and
energy of the color of light.)
 Activity 4: Which Color has the MOST energy?
(Students able to infer that the energy of the colors of light increases as one
goes towards the right side of the color spectrum and red light has the least
energy and blue light has the most energy.)
 Activity 5: The Spectrum Wheel....Revisited...
(Students will be able to infer that light is composed of colors of light of
different frequencies and wavelength; the frequencies of the colors of light
are inversely proportional the wavelength; the product of frequency and
wavelength of the color lights is a constant; and the arrangement of colors of
light shows the hierarchy of the color of light’s corresponding energy.)
 Activity 6: Scientific Explanations behind my Beliefs...
(Students should be able to come up with a presentation of the scientific
explanations of certain superstitious beliefs related to observable phenomena
in the sky.)

58
Motivation
 The facilitator may introduce a character named Roy G. Biv. Ask students
whether they are familiar with the character. Ask them also if there is a
connection between the character and the lessons. Ask the students if they
could guess some information or concept from the name of the character. If
the students recognize the colors of light then ask key question no. 3. Follow
it up by the 1st
2 key questions.
 As a brief review, introduce the concept of apparent depth and the concept of
refraction of light. Have a recall of the equation for index of refraction and let
them do Activity No. 1.
 Introduce the concept of dispersion as a special kind of refraction. Let them
perform Activity no. 2 which will give students more information about how
visible light refracts in different optical densities resulting to different colors of
light. This activity is composed of two parts. One makes use of locally
available materials while the other makes use of the standard materials like
prism and artificial source of light. A comparison of the two may be
highlighted during the discussion of results.
 The facilitator may let the students present their outputs per group and
processing be done after all the groups have presented by culling ideas and
concepts from the presented data and probing students to arrive at the
concept of colors of light.
 From the students’ outputs in Activity No. 2, the facilitator may ask why a
certain hierarchy of colors of light is observed. Then introduce Activity No. 3
and let the students perform the activity to determine which is really more
bent: the red light or the violet light. This will be explicitly described by the
students during the processing when they present their outputs which would
include the relation of the bending and the index of refraction of the color of
light.

59
 The facilitator may let the students present their outputs per group and
processing be done after all the groups have presented by culling ideas and
concepts from the presented data and probing students to arrive at the
concept that blue is bent more or violet is bent more than red light.
 Then ask the students which color of light gives the most energy. Let them
predict – red or violet light. Let them perform Activity No. 4. The facilitator
may let the students present their outputs per group and processing be done
after all the groups have presented by culling ideas and concepts from the
presented data and probing students to arrive at the concept that blue or
violet has the highest energy and red has the least.
 Ask the students on which other characteristics of color of light does energy
of colors depend on to introduce Activity No. 5. This activity was already done
in Grade 7. The focus of the activity in Grade 7 was to identify the
corresponding frequency and wavelength of the each color of light and the
computation of the speed of each of the colors of light. This time the focus is
on how energy relates to the frequency of the colors of light. From the given
materials, students will be able to determine the relationship between
frequency and the energy of the colors of light. Then the facilitator may ask
which is really more bent the red light or the violet light?
 Then ask them some inferences on how rainbows are formed. Ask them also
some superstitious beliefs that the students are familiar of related to the
existence of rainbows.
 Let them identify all the major concepts they were able to grasp from activity
nos. 1, 2, 3, 4, and 5 to build a concept on how rainbows are formed. Then let
them do Activity No. 6.
 Let the students present their outputs per group. Then go back to the key
questions to be able to summarize the concepts on visible light.

60
Q1. RED, ORANGE, YELLOW, GREEN, BLUE, VIOLET
Q2. From Top to Bottom: Red, Orange, yellow, Green, Blue, Violet
Q3. The refractive index of prism varies with the wavelength or color of the light
used. This causes the different colors of light to be refracted differently. Then
leave the prism at different angles, creating an effect similar to a rainbow
Q4. Some colors visible in the prism were not observed in the water
Q5. Small value for refractive index is observed in red and large refractive index
for red
Q6. The refractive indices of the different color of light indicate that light of
different colors travels at different speeds in the prism which accounts for the
different amounts of bending. Thus, blue light with greater refractive index
refracts more and appears at the bottom of the red light
Q7. Yes
Q8. RED, ORANGE, YELLOW, GREEN, BLUE, VIOLET
Q9. BLUE LIGHT
Q10. The greater the refractive index of the color of light, a greater bending is also
observed.
Red vs Violet...
Activity
3
The colors of the rainbow
Activity
2

61
Q11. RED
Q12. Violet
Q13. Violet
Q14. RED
Q15. RED
Q16. Violet
Q17. VIOLET, VIOLET
Q18. RED, RED
Q19. The wavelengths and frequencies of the colors of light vary. The wavelength
decreases from red to violet while the frequency increases from red to violet.
Q20. White light separates into color light because it refracts with different
refractive indices while passing through a medium like a prism.
Q21. YES
Q22. As the frequency of the color of light increase, the energy also increases. Red
has the least frequency with the least energy and Violet has the highest
frequency and the highest energy.
Q23. The higher the frequency of the color of light, the greater is its energy.
The color spectrum wheel
revisited
Activity
5
Which color has the most
energy?
Activity
4

62
References
Hewitt, Paul. (1989). Conceptual physics (6th
Ed.) London: Scoot, Foresman and
Company
http://users.hal-pc.org/~clement/Simulations/Mixing%20Colors/rgbColor.html
http://www.cs.brown.edu/exploratories/freeSoftware/repository/edu/brown/cs/explorat
ories/applets/combinedColorMixing/combined_color_mixing_java_plugin.html
http://www.shs.d211.org/science/faculty/MJP/s369/light/docs/RayDiagrams.htm

65
UNIT 2: Earth and Space
Overview
What will students learn about Earth and Space in Grade 8? As in the
previous grade, there will be three modules in this quarter: Module 1 is about
Earthquakes and Faults. Module 2 is on Understanding Typhoons, and Module 3 will
be about the Other Members of the Solar System.
In Module 1, we continue to emphasize the idea that our location on the
globe is intertwined with what we experience in our daily lives. For instance, the
Philippines is located along the Ring of Fire. This means that earthquakes and
volcanic eruptions are normal occurrences in our country.
We share the same fate with other countries that surround the Pacific
Ocean, including Indonesia to the south and Japan to the north. They too have
faults in their land where energy is locked for some time before it is unleashed in
devastating earthquakes.
Similar to our two neighboring countries, we are surrounded by the sea.
And whenever the seafloor is suddenly jolted by a strong earthquake, a tsunami
is generated and our coastal areas are swamped with deadly waves. Mindanao
and Mindoro have been victims in the not-so-distant past.
In Module 2, we find out why we are prone to typhoons, too. In fact, The
Philippines is hit by about 20 tropical cyclones each year. This number is an
average, so sometimes we get more than that. What conditions in the vicinity of
our country favor the formation of tropical cyclones?
Our country is located near the equator, surrounded by bodies of water.
This combination means there is heat to warm up the waters of the ocean and
produce a lot of water vapor. The rising warm air will soon turn into a low-
pressure area that may intensify into a tropical cyclone.
If only the Philippines were at a higher latitude, it would suffer less
tropical cyclones because the surrounding waters would be colder. Or if the
Philippines were at the equator, it would likely be free of tropical cyclones
because there is no Coriolis force to make the air spin.

66
Or if only there was a landmass in the way that would dull the edge of a
tropical cyclone that came in from the Pacific. Alas, there is no such luck. The
Philippines is located right where tropical cyclones form and there is nothing to
do but learn how to survive their annual onslaught.
In Module 3, we will take up comets, asteroids, and meteors. Luckily, the
Philippines is not a favored target. But even without a direct hit, everyone will be
affected if a really large chunk of rock came crashing from outer space. The last
time that happened, it ended the reign of the dinosaurs. So studying these
foreign objects may pay off in the long run.

67
EARTHQUAKES AND
FAULTS
In Grade 7, the students learned that the Philippines is one of the countries
located along the Ring of Fire. The Ring of Fire refers to the region around the
Pacific Ocean that are commonly hit by earthquakes and volcanic eruptions.
Earthquakes will be covered in this grade level while volcanic eruptions will be
tackled in the next.
Every now and then, a strong earthquake hits the Philippines, leading to
numerous deaths and widespread destruction. We cannot stop this natural event
from occurring. And up to now, scientists have not found a way to predict when an
earthquake will occur. Thus, students must learn about earthquakes in order to
survive.
What is a Fault?
Earthquakes occur when rocks along a fault suddenly move. The first thing to
do then is to learn what a fault is. A fault is a break in the Earth’s crust along which
significant movement has taken place. Let us go through the definition in more detail.
The word “break” refers to a crack in the ground. The word “crust” refers to
the outermost layer of the Earth. We live on the surface of the crust. “Significant
movement” means that the rocks have been displaced or shifted considerably.
Why do earthquakes occur?
What is the relationship between earthquakes and faults?
Unit 2
MODULE
1

68
Activity 1 is short and easy to do. All that is needed are sand and two pieces
of cardboard and the students are ready to go. Tell the students to work on top of the
newspaper to avoid sand spilling everywhere. The activity is supposed to simulate
what the ground looks like as rocks move along a fault.
Teaching Tips
1. Figure 1A is the starting point. Lay the two sheets side to side. Make the sand
top flat so everything can be seen clearly. The two parallel lines are there so
that the displacement will be obvious to the observer. Figure 1B, C, and D
shows how a crack forms in the sand.
A fault-y setup
Activity
1
Figure 1A-D. Sheets are moved in the direction shown by the arrows. A crack
forms in the sand and the lines are displaced.

69
2. Before doing this activity, experiment with sand of different sizes. If the sand
size is too big, the expected crack in the sand may not form or may be hard to
see. Look at Figure 1B, C and D. See the crack that goes from left to right? The
students are supposed to see that.
3. After the activity, direct the students to Figure 4 in the student module. (This is
Figure 2 in this guide.) Ask the students to compare what they saw in the
activity to what is shown in the picture. The students are supposed to see that
the crack in the sand is similar to the break across the road in the picture. You
can then tell them that that is how a fault may look out in the field.
Answers to questions
Q1. As you move the sheets, what is formed in the sand?
Answer: A crack, ‘line’ or break is formed in the sand.
Q2. What happens to the lines?
Answer: The lines are shifted or displaced.
Figure 2. An example of a fault (Image courtesy of the GEER Association
and National Science Foundation)

70
Figure 4. (Left) The short box cover is put within the long box
cover. (Right) Sand is poured into the nested covers.
For advanced classes
In Activity 1, the movement along the “fault” is in the horizontal direction. That
is, the “ground” moves sideways. You can also demonstrate movement in the vertical
direction. The ground will be observed to move up or down. All that is needed is sand
and a narrow box cover.
1. Get the box cover and cut it so that the length of one piece is twice the other
(Figure 3). If you cannot find a box cover, make one using cardboard.
2. Place the shorter box cover within the longer one (Figure 4, left photo). Put
sand in the nested box covers. Shake the box side to side so the surface of the
sand will become level (Figure 4, right photo).
3. Now, slowly pull the sides of the box covers as shown in Figure 5. Ask the
students to observe carefully.
Figure 3. Sand and a narrow box cover cut into two pieces

71
Figure 5. The box covers are pulled outward.
Figure 7. The box covers are pushed toward each
other.
Figure 6. (Left) As the box covers are pulled outward, cracks form in the sand.
(Right) With more outward pulling, the sand subsides.
As you can see in Figure 6, two parallel cracks form in the sand. If you continue to
pull, the sand in the middle of the cracks will subside (move down), forming a
depression. This simulates what happens when the ground is pulled apart by forces
within the Earth. Faults form, a portion of the land sinks, and a valley is formed.
5. Now, re-assemble the box covers as before. Do not forget to make the surface
of the sand flat. This time, push the sides of the box covers toward each other
(Figure 7). Let the students observe what happens.

72
Figure 8. (Left) A tiny hump is formed in the sand. (Right) The hump as seen
from another angle.
As can be seen from Figure 8, the opposite happens. Instead of the sand
sinking, the sand forms a tiny ridge. Unfortunately, this model does not show a crack
in the sand that would represent a fault. In the real world, a fault is formed when the
ground is squeezed by forces from inside the Earth. A portion of the land is pushed
up, and mountains are formed.
Note: Use fine sand when performing this demonstration. Coarse sand does
not work as well. Experiment using different materials.
How do faults produce quakes?
Now that students have an idea of how faults look, let us show them how
earthquakes occur along faults. To answer this question, the students will perform
two short activities.
In this activity, two small boxes are needed. The cartons that fruit juice drinks
are packaged in are perfect. Setting it up is simple (Figure 9, left photo). The activity
can be performed in groups, or as a class demo if you are pressed for time. The
activity is supposed to show the sudden jerk that occurs when rocks move along a
fault in an earthquake.
Stick ‘n’ slip
Activity
2

73
Figure 9. (Left) Setup before simulated earthquake (Right)
After simulated earthquake.
Teaching Tips
1. The students may find it tricky to attach the rubber band to the box. Just punch
two holes in the box, close enough so you can loop a paper clip (or a thin wire)
through them. Then attach the rubber band to the clip.
2. Look at the photos in Figure 9 so you know how it should be done. The student
is supposed to pull on the rubber band attached to one box while holding the
other box in place. The rubber band should be pulled forward and horizontally,
not sidewise, upward or downward.
3. Expected result: The box will not move at first because it is taped to the other
box which is being held. The rubber band will stretch. The tape will suddenly
come off. The box attached to the rubber band will jerk forward and the house
will topple over (Figure 9, right photo). This simulates the sudden movement
that occurs along a fault.
4. The success of this activity depends on the tape, which represents friction in
real life. If it is too sticky, the tape will never come off, no matter how much the
rubber band is pulled. Tape it on just enough for the rubber to stretch a bit
before the box jerks free from the tape.
5. In real world terms, this is what happens. Energy from inside the Earth exert a
force on the rocks along faults. But the rocks do not move right away because
of friction. The roughness of the rocks keeps them from slipping past each
other. But when the limit is reached, the rocks suddenly slip—earthquake!

74
Q3. What happens to the rubber band?
Answer: The rubber band stretches.
Q4. What happens to the box attached to the rubber band?
Answer: The box jerks forward.
Q5. What happens to the “house”?
The “house” falls over.
Q6. Which is the “fault” in this setup?
The “fault” is the boundary between the two boxes.
While Activity 2 simulates the sudden movement along a fault, it does not
show the shaking that accompanies the sudden movement. Activity 3 will
demonstrate this.
This activity needs the simplest of materials: just two plastic rulers and some
clay. The activity is supposed to demonstrate the shaking that occurs when the rocks
along a fault suddenly jerk free from being locked in place.
Teaching Tips
1. Even if this activity is simple, it should be tried out first before doing it in class.
What is expected to happen? The rulers are held together at the ends by a bit
of clay (Figure 10). The rulers are then bent into an S-shape. When the
bending goes beyond a certain limit, the rulers separate, vibrating in the
process.
Stick ‘n’ shake
Activity
3

75
Figure 10. The right ruler is pushed away while the left one is pulled back
until the rulers are bent into an S.
2. Choose rulers that vibrate nicely. If the plastic rulers are stiff, they will not
vibrate. If the rulers are too soft, they will bend without separating. It is best if
the rulers are of the same kind and length. The rulers must be held tightly. If
they are held loosely, the rulers will not vibrate.
3. Experiment to find out the right amount of clay and how much the rulers should
be pressed together. If you use too much clay, it will take a long time before the
rulers separate. But if you use too little, they will separate before there is any
bending, and vibration will be less.
4. It is challenging for students to transfer what they learned in an activity to real
life. You could use the following drawings (Figure 11) to make this activity more
concrete. Let the students imagine the rulers to be rocks making up the ground.
Drawing A shows the land before fault movement. In B, the rocks have
undergone some bending. In C, friction has been overcome and the rocks have
snapped straight from their bent position. This “snap and shake” motion is not
possible to show in a drawing or picture. It is this motion that is demonstrated by the
vibrating rulers.

76
Figure 11. When bending is too much, the rulers snap straight and
vibrate.
Figure 11. A, before fault movement. B, rocks bend, storing
energy. C, friction is overcome, rocks snap straight, releasing
energy in the form of earthquakes.
Q8. What happens when bending becomes too much?
Answer: The rulers separate and vibrate (Figure 11).

77
Figure 12. (Left) The Fault Model consists of two pieces that fit together. (Right)
The planar surface where the focus is located is the fault plane.
Focus and Epicenter
The students now know what a fault looks like. They also know that forces
from inside the Earth make the rocks along a fault move. But friction prevents the
rocks from moving right away. The rocks are stuck together. When a certain limit is
reached, the rocks suddenly slip and shake, and an earthquake is born. But where
exactly does the earthquake begin?
In this activity, the students will make a paper model of a fault. They will learn
the meaning of focus and epicenter. The latter term is always mentioned in news
reports about earthquakes. But do students know what it means? They will also
manipulate this model to explore the different ways that fault movement can occur.
Teaching Tips
1. For easier handling, the Fault Model may be pasted on a folder or cardboard
before cutting it out. The model is made of two pieces that fit each other. Each
piece has a top and sides but no bottom. When the model is assembled it will
look like Figure 12 (left photo).
Where does an earthquake start?
Activity
4

78
2. Just go through activity with the students, providing clues and guide questions
along the way. It should be clear to the students that the model represents a
portion of the ground. The upper surface of the model represents the surface of
the Earth. To emphasize this, you may cut a small human figure and paste it on
top of the model.
3. Let the students read the definition of a fault line (it is in the activity) and ask
them to point it out in the model. The “break” between the two pieces of the
model is the “fault.” But we can only see the part of the fault that is exposed at
the Earth’s surface. That is the broken line at the top of the model. That
represents the fault line (Figure 13).
4. Next, ask the students to identify the fault plane. The definition provided in the
activity will serve as a clue. If you separate the two pieces, the “fault plane” can
be seen. This is the flat surface where the focus is (Figure 12, right photo).
Fault movement occurs along the fault plane.
5. Next, ask the students to point out the focus and explain what it is. The focus is
the place where the first break happens, where the fault starts to slip, where
first movement takes place. It is the starting point of the earthquake.
6. Next, ask the students to locate the epicenter. The epicenter is on the surface
of the Earth directly above the focus. Figure 13 shows the location of the
epicenter (marked with a star) in the model. If a person stood on the epicenter,
the focus would be directly below him at the fault plane. Use Figure 15 to show
how the focus and epicenter are related in space.
Figure 13. The epicenter (marked with
a star) is the spot on the surface of the
Earth directly above the focus.

80
Figure 15. The place where the earthquake starts is called the focus. The focus is
underground, along the fault plane. The spot on the surface of the Earth that is
directly above the focus is called the epicenter. The trace of the fault is also known
as fault line.
Q9. Use your model to show different types of movement along a fault. How
would the surroundings be affected?
Answer: See Figure 16. Models A and B show horizontal movement.
Suppose a road is built across the fault, sooner or later, it would be displaced
sideways.
Models C and D show vertical movement. In Model C, a portion of the
“ground” dropped down, forming a low area. In Model D, part of the “ground”
was raised, forming a high region.
Figure 16. Using the model to show different fault movements.

81
How Strong is the Earthquake?
Scientists use two different ways to describe how powerful an earthquake is.
One way is by noting the effects of the earthquake on people, structures, and the
surroundings. This is called the intensity of the earthquake. The Philippine Institute of
Volcanology and Seismology (PHIVOLCS) uses the following scale to describe the
intensity of earthquakes in the Philippines.
Table 1. PHIVOLCS Earthquake Intensity Scale (PEIS)
Intensity
Scale Description
I
Scarcely Perceptible - Perceptible to people under favorable
circumstances. Delicately balanced objects are disturbed slightly. Still
water in containers oscillates slowly.
II Slightly Felt - Felt by few individuals at rest indoors. Hanging objects
swing slightly. Still water in containers oscillates noticeably.
III
Weak - Felt by many people indoors especially in upper floors of
buildings. Vibration is felt like one passing of a light truck. Dizziness
and nausea are experienced by some people. Hanging objects swing
moderately. Still water in containers oscillates moderately.
IV
Moderately Strong - Felt generally by people indoors and by some
people outdoors. Light sleepers are awakened. Vibration is felt like a
passing of heavy truck. Hanging objects swing considerably. Dinner,
plates, glasses, windows, and doors rattle. Floors and walls of wood
framed buildings creak. Standing motor cars may rock slightly.
Liquids in containers are slightly disturbed. Water in containers
oscillate strongly. Rumbling sound may sometimes be heard.
V
Strong - Generally felt by most people indoors and outdoors. Many
sleeping people are awakened. Some are frightened, some run
outdoors. Strong shaking and rocking felt throughout building.
Hanging objects swing violently. Dining utensils clatter and clink;
some are broken. Small, light and unstable objects may fall or
overturn. Liquids spill from filled open containers. Standing vehicles
rock noticeably. Shaking of leaves and twigs of trees are noticeable.

82
VI
Very Strong - Many people are frightened; many run outdoors. Some
people lose their balance. Motorists feel like driving in flat tires. Heavy
objects or furniture move or may be shifted. Small church bells may
ring. Wall plaster may crack. Very old or poorly built houses and man-
made structures are slightly damaged though well-built structures are
not affected. Limited rockfalls and rolling boulders occur in hilly to
mountainous areas and escarpments. Trees are noticeably shaken.
VII
Destructive - Most people are frightened and run outdoors. People
find it difficult to stand in upper floors. Heavy objects and furniture
overturn or topple. Big church bells may ring. Old or poorly-built
structures suffer considerably damage. Some well-built structures are
slightly damaged. Some cracks may appear on dikes, fish ponds,
road surface, or concrete hollow block walls. Limited liquefaction,
lateral spreading and landslides are observed. Trees are shaken
strongly. (Liquefaction is a process by which loose saturated sand
lose strength during an earthquake and behave like liquid).
VIII
Very Destructive - People are panicky. People find it difficult to stand
even outdoors. Many well-built buildings are considerably damaged.
Concrete dikes and foundation of bridges are destroyed by ground
settling or toppling. Railway tracks are bent or broken. Tombstones
may be displaced, twisted or overturned. Utility posts, towers and
monuments may tilt or topple. Water and sewer pipes may be bent,
twisted or broken. Liquefaction and lateral spreading cause man-
made structure to sink, tilt or topple. Numerous landslides and
rockfalls occur in mountainous and hilly areas. Boulders are thrown
out from their positions particularly near the epicenter. Fissures and
faults rupture may be observed. Trees are violently shaken. Water
splash or slop over dikes or banks of rivers.
IX
Devastating - People are forcibly thrown to ground. Many cry and
shake with fear. Most buildings are totally damaged. Bridges and
elevated concrete structures are toppled or destroyed. Numerous
utility posts, towers and monument are tilted, toppled or broken.
Water sewer pipes are bent, twisted or broken. Landslides and
liquefaction with lateral spreadings and sandboils are widespread. the
ground is distorted into undulations. Trees are shaken very violently
with some toppled or broken. Boulders are commonly thrown out.
River water splashes violently or slops over dikes and banks.

83
X
Completely Devastating - Practically all man-made structures are
destroyed. Massive landslides and liquefaction, large scale
subsidence and uplift of land forms and many ground fissures are
observed. Changes in river courses and destructive seiches in large
lakes occur. Many trees are toppled, broken and uprooted.
When an earthquake occurs, different places will have different intensities.
That is because different areas will experience different degrees of shaking. Near the
epicenter, shaking is great, so the intensity there will be high. Away from the
epicenter, the intensity is less.
The intensity also depends on the type of material that makes up the ground.
If the ground is made of solid rock, it will shake less. In comparison, loose materials
such as sand and silt will undergo greater shaking and will result in more damage.
Scientists have another way of describing how strong an earthquake is. They
measure the energy that is released in an earthquake. This is called the magnitude
of the earthquake. Magnitude scales use Hindu-Arabic numerals while intensity
scales use Roman numerals.
Magnitude 2 earthquakes are weak. Only instruments are sensitive enough to
“feel” them. Magnitude 4 quakes are strong enough to be felt by most people.
Magnitude 6 earthquakes can cause a lot of damage in populated areas. Magnitude
9 quakes are so powerful they can destroy whole communities at the epicenter.
Do You Live Near an Active Fault?
In this part of the module, the students are taught how to use a map to find
out if there is an active fault near their community. Active faults are those that have
moved and caused earthquakes in the past and are expected to do so again in the
future. In relation to this exercise, the students must participate in an earthquake drill
to be arranged by the school.
Teaching Tips
1. Now that students know that earthquakes originate from faults, the obvious
question is, where are these quake-producing faults? Where are they located?
These faults have been mapped by PHIVOLCS and the map is available to the
public (Figure 17).
2. The first thing to do is to familiarize the students with the map of the
Philippines. The students should be able to point out the different provinces in
their own region.

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3. Next, the students must know what the lines on the map mean. Solid lines tell
us exactly where the active faults are. Heavy dashed lines tell us the
approximate location of active faults. The meanings of the other symbols are
found in the legend but they will be discussed in detail in Grade 10.
4. The task of students is to use the map to locate the nearest active faults that
may affect their town. Those who live close to active faults must be extra
prepared for earthquakes. PHIVOLCS recommends doing the following:
Before the earthquake
Prepare homes or schoolrooms by strapping heavy furniture to the walls.
Check the stability of hanging objects. Breakable items, harmful chemicals and
flammable materials should be stored properly. Know exit routes.
Know where fire extinguishers and first aid kits are located. Prepare an
emergency supply kit that includes water, canned food, can opener, clothing,
blanket, battery-operated radio, flashlight, and extra batteries. Participate in
regular earthquake drills.
(Note: Earthquake drills should be led by school authorities.)
During the earthquake
Stay calm. If you are at home or inside a building, stay there. Duck under a
sturdy desk or table and hold on to it. Stay away from glass windows, cabinets,
and heavy objects. Beware of falling objects.
If you are outside, move to an open area. Stay away from trees, powerlines,
and concrete structures. Move away from steep slopes which could be affected
by landslides. If you are near the shore, move quickly to higher grounds.
Tsunamis may follow.
After the earthquake
Do not use elevators or enter damaged buildings. Check yourself and others
for injuries. Check for spills of chemical, toxic, and flammable materials. If you
need to evacuate, leave a message and bring your emergency kit. Listen to the
radio for updates.
What to do before, during, and after an earthquake is part of the Earthquake
Preparedness Guide which can be downloaded from the PHIVOLCS website. How to
conduct an earthquake drill is too long to reproduce here and can be downloaded
from the same site. If this is not possible, please request assistance from the local
PHIVOLCS station and other government agencies.

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Figure 17. Active Faults and Trenches

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Figure 18. (Left) Setup for the tsunami activity. (Right) The plastic panel is jerked
upward.
Earthquakes and Tsunamis
Faults are found on land as well as at the bottom of the sea. When an
underwater fault suddenly moves, a tsunami may be formed. But not all fault
movements generate tsunamis. If the fault moves sideways, the water above it will
not be disturbed. The movement has to be in the vertical sense, a sudden upward or
downward motion.
In this activity, the students will simulate the sudden upward movement of
rocks along a fault at the seafloor. The sudden push upward will disturb the water,
forming a wave.
Teaching Tips
1. The materials needed for this activity are simple. A laundry tub or batya can be
a substitute for the plastic tray shown in the photos. A piece of plywood can be
used instead of the plastic panel.
2. Make sure the students will observe the following: a) When the plastic panel is
jerked upward, a wave is formed; b) the wave travels toward the rock; c) the
wave runs up the side of the rock.
Tsunami!
Activity
5

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Figure 19. (Left) Before the wave reaches the rock, the water level by the rock goes
down. (Right) When the wave reaches the rock, the water level rises.
3. Find the best way to jerk the plastic panel up so that a nice wave is formed.
Between jerks, wait until the surface of the water is calm.
4. People often use the term tidal waves when they talk about tsunamis. This is
not right. Tsunamis are due to the sudden upward (or downward) movement of
rocks along a fault at the seafloor. Tsunamis are not related to tides, which are
caused by the action of gravity.
5. The reason a tsunami is so powerful is because the wave involves the whole
depth of the ocean, not just the water on the surface. And why does a tsunami
rise to such great heights when it reaches the shore?
The wave is long, about 100 km or so. When the “front” end reaches the shore,
it slows down. But the “tail” end keeps on coming at great speed. So the water
piles up and grows to dangerous heights, destroying everything in its path.
6. The Philippines is no stranger to tsunami. Mindanao had been affected by a
devastating tsunami in 1976; Mindoro was struck in 1994. For more information
about tsunamis, visit the PHIVOLCS website.
Q10. What was formed in the water by the sudden push of the plastic panel?
Answer: A wave was formed by the sudden push.
Q11. How was the water level by the rock affected by the wave?
The water level went up.
Q12. What does the water represent? How about the rock?
The water represents the sea. The rock represents land.
Q13. What does the plastic panel represent?
The plastic panel represents the rocks that suddenly move along an
underwater fault.

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What’s Inside the Earth?
Earthquakes are always linked with death and destruction. Is there anything
good at all about earthquakes? Well, scientists have used earthquake waves to
figure out the internal structure of the Earth.
When an earthquake occurs, vibrations or seismic waves start off from the
focus and travel in all directions. The seismic waves travel through the Earth and
carry information from the interior to the surface.
For instance, when seismic waves encounter a layer within the Earth, they
are reflected. Like an echo, seismic waves are bounced back. They are also
refracted or bent. This is how we know that the Earth has a crust, mantle, and core.
We know that the rocks get more dense with depth because the seismic
waves speed up as they pass through these rocks. We know too that there are
partially molten regions in the mantle because seismic waves slow down in those
areas.
Scientists have found out that one type of seismic wave, s-waves, cannot
travel through liquids. Since s-waves disappear when they reach the core, that
means the outer core must be molten (liquid).
Thus, scientists know about the Earth’s interior because of the occurrence of
earthquakes. But a more detailed description of the Earth’s internal structure will be
made when plate tectonics is taken up in Grade 10.
References
Brady, J.E., & Senese, F. (2004). Chemistry: Matter and its changes (4th
ed.). River
Street Hoboken, NJ: John Wiley & Sons, Inc.
Links
http://www.youtube.com/watch?v=2uJN3Z1ryck&feature=player_embedded
(Tsunami in Japan 3.11 first person full raw footage)

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UNDERSTANDING
TYPHOONS
In the lower grades, we have taken up the following so far: types of weather;
how to measure weather components; characteristics of some weather disturbances;
patterns in the weather; and why we have seasons. In this grade level, we are
focusing on one of the weather disturbances that takes place in the Philippines every
year: tropical cyclones.
A lot of people are not familiar with the term tropical cyclone. This is the
reason why we are using the common word typhoon at the start to serve as a jump-
off point. Hopefully, the students will see the distinction right away, that a typhoon is
just one category of tropical cyclones.
There are three activities in this module: a) Plotting the Philippine Area of
Responsibility; b) Tracking a Tropical Cyclone; and c) Dissecting a Tropical Cyclone.
The module ends with the signals that the Philippine Atmospheric, Geophysical, and
Astronomical Services Administration (PAGASA) uses in warning the people during
severe weather.
What is a Typhoon?
First, we have to clear up the meaning of some terms. Begin by asking the
students what they commonly experience during typhoons. Floods and landslides
may come up. But we will focus on two answers: excessive rain and strong winds.
Why is the Philippines prone to typhoons?
What conditions favor the formation of typhoons?
Unit 2
MODULE
2

90
Then show the students a picture of a typhoon taken from a satellite high
above the Earth. (Figure 1 shows a supertyphoon but a typhoon looks the same.)
The students are expected to see that the clouds are going around the center of the
typhoon in a spiral. Explain that the clouds are being blown by strong winds.
Figure 1. Supertyphoon Melor, 2009
Image by NASA Earth Observatory
Thus, apart from rain clouds, typhoons are characterized by winds that go
around a center. To support the point, show the students some newspaper clippings
or let them listen to recordings of radio or tv advisories about typhoons. The
weatherperson always states the speed of the wind.
At this point, introduce Table 1. Explain that we call bagyo is called tropical
cyclone by scientists. A tropical cyclone is just a system of thunderstorms that move
around a center.
The public uses the word bagyo for all types of tropical cyclones. But
scientists have subdivided tropical cyclones into four categories depending on the
speed of the wind.
Thus, when a tropical cyclone has a low wind speed, no more than 64
kilometers per hour (kph), it is called a tropical depression. If the wind speed is from
65 to 118 kph, then it is a tropical storm.
If the tropical cyclone has a wind speed from 119 to 200 kph, it is called a
typhoon. And if the wind speed is more than 200 kph, it is categorized as a
supertyphoon (Table 1).

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Figure 2. Bottles, caps, and masking tape
Table 1. Tropical cyclone categories
Category
Maximum Wind Speed
kilometers per hour (kph)
Tropical Depression 64
Tropical Storm 118
Typhoon 200
Supertyphoon greater than 200
Demonstration
At this point, show a video or animation of a tropical cyclone where the clouds
are moving around the center, so the students will get a more concrete idea of how
this happens.
Alternatively, you can give a demonstration that will simulate the movement
of winds around a center in a tropical cyclone. You will need two plastic bottles with
caps, masking tape, and a drill.
Place the two caps back to back. Wrap them with masking tape (Figure 2).
Wrap the tape around several times to make the connection strong and leak-proof.
Drill a hole through both of them. If you do not have a drill, use a heated nail to make
a hole.
Fill one bottle with water. Then screw one of the caps onto the bottle. Then
screw the other bottle onto the other cap. You should get the setup in Figure 3, left
photo.

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Figure 3. (Left) One bottle filled with water. (Right) Water swirls around
as it spills into the other bottle.
Now, turn the whole setup so the filled bottled is on top. Shake the filled bottle
with a circular motion (counter-clockwise) until a whirlpool is formed in the water
(Figure 3, right photo).
In this simulation, the water represents the wind going around the center of a
tropical cyclone. In the northern hemisphere, the winds blow in a counter-clockwise
direction. In the southern hemisphere, the winds spin around in the opposite
direction, clockwise.
The “funnel” in the center of the spinning water represents the “eye” of a
tropical cyclone. When scientists talk about the location of a tropical cyclone, they
are referring to the location of the eye.
Philippine Area of Responsibility
PAGASA starts monitoring tropical cyclones even before they enter the
Philippine Area of Responsibility (PAR). But everything shifts into high gear when the
weather disturbance is already inside the PAR. The PAR includes a big area east of
the Philippines because this is where most tropical cyclones come from.
In the following activity, the students are required to plot the PAR on a map.
They already learned how to plot latitude and longitude in Grade 7. If the students
are a bit rusty, perform some drills.
Plotting the PAR
Activity
1

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Figure 4. Philippine Area of Responsibility (PAR)
Teaching Tips
1. Activity 1 can be done in groups or as a class activity. Have the map enlarged
and post it on the board. Call on students to come to the front and plot the
points. There are six points to plot, meaning there are six pairs of latitude and
longitude. So each point may be plotted by two students, one will find the
latitude and the other the longitude.
2. Note that the eastern boundary of the PAR is much farther from the country
than the western boundary. That is because most tropical cyclones that hit the
Philippines come from the Pacific Ocean. The wide area gives us more time to
prepare before the tropical cyclone hits land.
In the map below, the bold line marks the boundary of the Philippine Area of
Responsibility. The latitude and longitude of each corner is also shown.

94
Q1. If a typhoon is located at 15°N, 138°E, is it within the PAR?
Answer: No, the typhoon is outside the PAR.
Q2. How about if the typhoon is at 19°N, 117°E, is it inside the PAR?
Answer: No, the typhoon is outside the PAR.
Under What Conditions do Tropical Cyclones Form?
Now that the students know where PAR is, it is time for them to learn why
tropical cyclones keep on developing near our country. What conditions are present
in the vicinity of the Philippines that allow the development of tropical cyclones?
Show the following maps to the students. The maps are from the PAGASA
website. They show the tracks or paths of four tropical cyclones that entered the
PAR in the early to mid-2000s. Guide the students in answering the following
questions:
Where did the tropical cyclones form? On land or in the ocean?
Before asking the question, make sure that the students still remember the
landmasses and bodies of water in the vicinity of the Philippines. If the students have
already forgotten, a short review may be in order.
It is clear from the maps that all four tropical cyclones started out in the
Pacific Ocean. Tropical cyclones usually form where there is warm water. The
temperature should be 26.5°C or more.
The warm ocean water heats up the air above it. The warm air then rises.
The rising warm air results in a low-pressure area. Air in the surroundings will then
move toward the area. This was taken up in Grade 7.
Now, there is water vapor in the rising warm air. The water vapor soon
condenses and heat is given off. The heat makes the air rise even more, and air in
the surroundings will keep coming in. The air starts to spin, and a tropical cyclone is
born.
What can you say about the temperature of the bodies of water in the vicinity
of the Philippines? Is the water warm or cold?
Our country is located near the equator. Thus, it is warm in the vicinity of the
Philippines, both on land and in the surrounding bodies of water. The warm water
supplies the water vapor that a tropical cyclone needs to keep it going.
In what direction did the tropical cyclones move?
From the map, the students can see that the tropical cyclones move in a
northwest direction. Not all tropical cyclones move this way. But this is the general
rule for those that start from the Pacific Ocean.

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But look at the track of Yoyong. At the end of its path, it curves to the
northeast. Many tropical cyclones in the PAR do that. Instead of going straight
toward Mainland China, they veer to the northeast and go toward Taiwan and Japan.
There are different reasons why this happens. One, there could be a low-
pressure area in that region. So the wind in the surroundings move toward that
region and the tropical cyclone is carried along. Remember, winds blow toward low-
pressure areas.
Another reason is there could be a high pressure area in the path of the
tropical cyclone. So the tropical cyclone cannot proceed and is diverted along a
different way.
Which part of the Philippines was hit by the four tropical cyclones?
All the four tropical cyclones hit northern Philippines or the island of Luzon.
Note where the tropical cyclones start: at the latitude of the Visayas and Mindanao.
So when a tropical cyclone moves to the northwest, it ends up in Luzon.
This is the reason why Mindanao is not commonly hit by tropical cyclones.
Unless the following happens: a) the tropical cyclone starts at a latitude closer to the
equator, or b) the tropical cyclone moves directly to the west, instead of moving to
the northwest. This is what happened in Mindanao in recent years.
In the case of Agaton, Yoyong, and Huaning, where did they die out? Near
land or in the middle of the ocean?
Tropical cyclones weaken when they hit land. They die out over land because
they need warm water to sustain them. They need water vapor to keep them going.
Even when the tropical cyclone is still in a body of water, it may weaken and die out if
the water is cold.

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Figure 5. Tracks (paths) of selected tropical cyclones
In the following activity, the students will work again with latitude and
longitude. But this time, they will apply their skill in plotting the track of a tropical
cyclone as it passes through the PAR.

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Unlike Luzon, Mindanao is not hit by tropical cyclones every year. This is why
people in Mindanao were caught by surprise when Sendong and Pablo came one
after the other in recent years.
In this activity, the students will plot the track of Tropical Storm Sendong
(International name: Washi). The students will use the map where they plotted the
PAR in Activity 1.
Teaching Tips
1. Ask the students to indicate which points are not within the PAR. The points
that are located at longitudes less than 115°E and more than 135°E will lie
outside the map. But even when a storm is still outside the PAR, PAGASA is
already monitoring it. And even when it has already left the PAR, there is still a
chance that it will return.
2. Like all tropical cyclones, Sendong formed in the Pacific Ocean from a low-
pressure area (LPA). It did not yet have a name at that point. Names are not
given to LPAs. Then the winds became stronger and the LPA became a
tropical depression. In other parts of the world, tropical depressions are not
given names; they may be given a designation such as 27W, for instance. On
the other hand, PAGASA gives names to tropical depressions.
Before Sendong crossed into the PAR, it had already become a tropical storm.
That means its winds have speeded up. Since it was already within the PAR,
PAGASA used its prepared list of names and called the tropical storm
Sendong.
3. Ask the students what was the effect on Sendong when it hit Mindanao.
Expected answer: Sendong weakened because it was cut off from the sea. Ask
the students further what was the effect on Sendong when it reached the Sulu
Sea. Expected answer: Sendong intensified again.
Sendong then headed for Palawan. But when it encountered cold air beyond
Palawan, Sendong finally died out.
Tracking a tropical cyclone
Activity
2

98
Figure 2. Bottles, caps, and masking tape
Figure 6. Track of Tropical Storm Sendong, 2011
Q3. Is it possible to plot all the points in the table on the map from Activity 1?
Answer: No, it is not possible. The points west of 115°E and east of 135°E
are beyond the coverage of the map from Activity 1.
Q4. Where did Sendong form?
Answer: Sendong formed in the Pacific Ocean.
Q5. When did Sendong enter the PAR?
Answer: Sendong entered the PAR on December 15, 2011.
Q6. When did Sendong leave the PAR?
Answer: Sendong left the PAR on December 18, 2013.
Q7. In what direction did Sendong move?
Answer: Sendong moved in a westward direction.

99
If you have the means, visit the following webpage and download the tracking
data of other powerful tropical cyclones such as Typhoon Pablo (International name:
Bopha): http://weather.unisys.com/hurricane/w_pacific/2011H/index.php. Tracking
data include the latitude and longitude needed for plotting.
The plotted tracks can be used as basis for discussing all sorts of questions
such as, Where do tropical cyclones commonly form? Or conversely, where do they
seldom develop? What paths do they take? Which provinces are usually hit? Where
do tropical cyclones intensify? Where do they weaken and die out?
Inside Tropical Cyclones
The strong winds brought by a tropical cyclone are very dangerous. Many
people have been hurt or killed by flying objects blown by powerful winds. And unlike
earthquakes, tropical cyclones cause a lot of agricultural damage, destroying plants,
trees, and crops that cost up to hundreds of millions of pesos.
In the following activity the students will look inside a tropical cyclone and find
out where the winds are strongest and therefore most unsafe.
In this activity, the students will compare the air pressure and wind speed at
different places within a tropical cyclone. They will see that within the eye, the winds
are slight. But at the eyewall, the winds blow at deadly speeds.
Teaching Tips
1. Many students are challenged when they have to imagine objects in three
dimensions. Before the students proceed to answer the questions, make sure
that they understand the drawing in Figure 7.
Dissecting a tropical cyclone
Activity
3

100
Figure 7. (Top) View of a tropical cyclone at an angle. (Bottom) Drawing of a
tropical cyclone in cross-section. (Top image by NASA Earth Observatory)
The top image is a tropical cyclone as seen from above but at an angle. The drawing
below it is a cross-section of a tropical cyclone. It is like cutting a cake in half and
looking at it from the side. But in this case we are looking at a tropical cyclone and
the clouds that make it up.
2. If the students need guidance in finding out the relationship between the table
of air pressures and the drawing, let them write the numbers in the table on the
drawing itself. For example, let them write 930 mb near letter A in the drawing;
960 mb near letter B; and so on. Then ask them if the air pressure is increasing
or decreasing toward the eye.
3. If the students need guidance with the table of wind speeds, let them do the
same as in the previous number. Help the students imagine “wind speed.” The
wind is invisible so it is hard to imagine how fast it is. Compare it to something
they know, such as the speed of a car on the highway—about 100 km/h.
4. If it is possible, bring an anemometer to class and let the students see how it
spins faster when wind speed increases.

101
Q8. Compare the air pressures at A, B, C and D. What do you notice?
Answer: The air pressure at A (within the eye of the typhoon) is less than the
air pressures at locations away from the eye.
Q9. Compare the wind speed within the eye and at the eyewall. What can you
say?
Answer: The wind speed at the eyewall is much greater than the wind speed
at the eye.
The activity is supposed to show that the air pressure is lowest at the eye of a
tropical cyclone. This is the reason why the surrounding air blows toward the eye. A
barometer will show decreasing air pressure as a tropical cyclone approaches.
In contrast, as a tropical cyclone comes nearer, the wind speed increases.
The wind speed is greatest at the eyewall, at the dense clouds surrounding the eye.
When PAGASA quotes a wind speed, it is referring to winds at the eyewall.
But at the eye itself, the wind is light. So when the eye is over an area, people
there think the weather has turned for the better. They may relax and lower their
guard. But the tropical cyclone is far from over.
As the tropical cyclone leaves, the other side of the eyewall can still do much
damage. That is because structures have already been battered earlier. It is just a
matter of time before something worse will happen.
Are You Prepared?
Tropical cyclones by themselves are already dangerous. But they also cause
other hazards. Those who live near hill and mountain slopes are susceptible to
landslides during stormy weather.
Those who live near the coast are vulnerable to storm surges. And those who
live in low-lying areas are helpless against flash floods. Remind students to always
listen to advisories and obey the authorities.
We end the module by familiarizing the students with the early warning
signals that PAGASA uses in their bulletins and advisories. There are four levels of
Public Storm Warning Signals. (Visit the PAGASA website for the complete texts.)
The phrase is rather long, so PAGASA shortens it to PSWS # 1, PSWS # 2, etc.
Each signal refers to a certain wind speed that will affect the locality. To
acquaint the students with the storm signals, collect some newspaper clippings and
let the students read these in class. Then ask them what corresponding wind speed
is expected given a certain signal. (If it is possible, record some radio broadcasts and
play them in class.)

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When a signal is raised for the first time, that means that the effect of the
tropical cyclone is still in the future. When PSWS # 1 is announced over a certain
area, the effect is expected within 36 hours. That is still one and a half days in the
future. People have time to prepare.
With PSWS # 2, the lead time (the time people have to prepare) is 24 hours;
PSWS # 3, 18 hours; and PSWS # 4, 12 hours. But the lead time is applicable only
when the signal is announced the very first time. If at a later time, the same signal is
broadcast, the lead time is now less because the tropical cyclone has already moved
closer.
To round up the lesson, ask the students to put together an emergency kit for
use at home. Water is the most important thing that should be included in the kit.
That is because during tropical cyclones, floods are likely to happen. And floods will
contaminate our usual water sources, especially in rural areas. Thus, clean drinking
water will be very hard to find during such times.
Tarbuck, E.J., & Lutgens, F.K. (2004). Earth Science (10th
ed.). First Lok Yang Road,
Singapore: Pearson Education (Asia) Pte Ltd.
http://www.pagasa.dost.gov.ph/
http://www.ready.gov/hurricanes
http://www.noaawatch.gov/themes/tropical.php
http://weather.unisys.com/hurricane/w_pacific/2011H/index.php
http://en.wikipedia.org/wiki/Tropical_Storm_Washi
http://people.cas.sc.edu/carbone/modules/mods4car/tropcycl/index.html
http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=40584

103
COMETS, ASTEROIDS,
AND METEORS
Recent advances in space technology have allowed scientists coming from
different background like physics, chemistry, biology, and geology to collaborate on
studying Near-Earth Objects (NEO) like comets and asteroids. With more powerful
telescopes and space probes, the study of comets and asteroids provides more
clues about the origins of our solar system. Over the past three years, amateur and
professional astronomers have discovered several NEO’s that came close to Earth,
the most recent asteroid being Asteroid 2012 DA14. It made a very close approach
to Earth as it orbited the Sun on February 16, 2012. On the morning of February 16,
2012, a meteoroid exploded in Earth’s atmosphere over Lake Chebarkul in Russia
hurting about 1,000 people in the process. These two events triggered superstitions,
fears, and doomsday prophecies held by different cultures. But do these things have
scientific basis?
Introduction
The pre-assessment activity will take 30-35 minutes of one class period. After
the pre-assessment activity, give an introduction about comets and asteroids for the
last 25-30 minutes of the period. In the introduction, focus on the comparison of key
characteristics of a comet and an asteroid. Use the Student Learning Material as a
guide for preparing your introduction.
Has Earth ever been hit by a comet or an asteroid? If yes,
how have such impacts affected Earth? How often does a
comet or an asteroid hit Earth?
Unit 2
MODULE
3

104
Pre-assessment Activity (Eliciting Prior Knowledge)
1. Give a pre-assessment of what students know about comets, asteroids, and
meteors. The following activities can be done. Choose the activity/ies which you
think would best match the ability and interest of your class.
a. Guessing game
Variation 1:
 Show three pictures (a comet, asteroid, and a meteor) to the class and
ask them if they recognize what these objects are. If the students cannot
recognize any of these three objects, tell them that one of the pictures is a
comet, an asteroid, and a meteor. Make them guess which object
corresponds to each picture.
 After the students give their guesses, tell them that in the course of the
unit, they will learn if their guesses are correct. Also, at the end of the
lesson, the group will be awarded points as part of their recitation grade
for every celestial object that they correctly identified.
Variation 2:
 Divide the class into smaller groups. Distribute to them three blank strips
of paper and a crayon (for writing).
 Tell the class that you will post a picture of a celestial object. The groups’
goal is to identify what this object is. They have 15 seconds to discuss as
a group to come up with their guess, and then they will write their answer
on the strip of paper.
 After 15 seconds, ask for a representative from each group to post their
paper strip on the board, just beneath the photo of the celestial object.
 Do this for the other two celestial objects (asteroid and meteor shower).
 After the students give their guesses, tell them that in the course of the
unit, they will learn if their guesses are correct. Also, at the end of the
lesson, the group will be awarded points as part of their recitation grade
for every celestial object that they correctly identified.
b. Brainstorming
 Divide the class into smaller groups. Give each group ½ Manila
paper/whole cartolina/old, big calendar and a crayon (for writing).
 Tell the groups to prepare a table with three columns (as shown below)
and write the following words on each column: comet, asteroid, and
meteor.
Group ________
What we know about…
Comets Asteroids Meteors

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 Tell the groups to list down everything they know about these terms in the
appropriate column. Give the class five (5) minutes to finish this.
 After five (5) minutes, call a representative from each group to post their
output on the board.
 Tell the class to examine the output of the other groups. Ask them if they
see similarities in the things they have listed about each term, and to
point out these things.
 Tell the class that in the course of the unit, they will learn if the things they
have listed under each term are correct. From time to time, you will ask
them to revise the things they have listed about each term as they learn
more about them.
c. Filling up a Venn Diagram
 Give the Venn Diagram activity found in the Pre/Post test part at the end
of this TG.
 Call representatives from each group to present their answers and
explain as necessary.
d. Story telling
 Call three to four volunteers to share about what they know or a past
experience about comets, asteroids, or meteors based on recent events.
This activity is a simulation of a comet or asteroid hitting Earth. Explain to the
class, while briefly going over the materials for the activity, what is being represented
by the materials. The coloured flour or starch represents Earth’s crust. The pebble
represents a comet, asteroid, or fragments coming from either a comet or an
asteroid. Remind the class that the activity is a group work. The group must arrive at
a common answer so they must all observe and take turns in making “pebble
craters”. Students may throw the pebble into the coloured flour at any angle and
position they want as long as the pebble hits the flour.
Teaching Tips
4. If you have internet access, there are many photos and video clips available
which you can download and save to show to the class. Some of them are
shown below.
What happens when a comet
or an asteroid hits Earth?
Activity
1

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5. Try out the student activity before performing it in class.
6. Prior to performing the activity, prepare materials for each group. Prepare
colored flour by mixing ordinary flour or starch with powdered food coloring,
plant extract, or dye (e.g., jobos). Adding color to the flour is done to make
observations of “pebble craters” easier to see. The rectangular container
should have the dimensions of at least 22.86 cm (9 inches) wide, 30.48 cm (12
inches) long, and 7.62 cm (3 inches) high. If a rectangular container is
unavailable, a round one can be used, about 30.48 cm (12 inches) in diameter
and 7.62 cm (3 inches) high.
7. Encourage the groups to repeat the activity several times to allow every
member the chance to perform the activity.
8. Make sure that the students make observations and discuss their answer to the
questions based on their observations.
9. Before asking the groups to share their observations and results, ask them
reflect on the activity they performed if they think they were able to do enough
trials, make good observations, had a genuine exchange of ideas to come up
with answers; and if their answers can be supported by evidence.
10. During the presentation of observations of all groups, encourage the students
to compare their observations and constructively scrutinize the observations
made by other groups.
11. Give feedback on the quality of their group work, focusing on delegation,
discussion, and team work at the end of the activity (oral or written).
12. Remind the students that they do not need to memorize names of comets and
asteroids.
Drawings a & b will depend on the students’ actual observations. They should be
assessed for the accuracy of the drawing. More or less, the pebble crater should
have a rounded shape but a slight oblong shape is also correct.
Q1: The answer will depend on the students’ actual observations. More or less,
they should see that the shape of the crater is similar to the ones shown in
the photos.
Q2: The plants and animals living in that area are most likely to have died on
impact.
Q3: An asteroid because it has a shorter orbital period and its origin is most likely
from the Asteroid Belt which is nearer than the Kuiper Belt and Oort Cloud.
 Module on Comets, Asteroids, and Meteors from the Canadian Space Agency:
http://www.asc-csa.gc.ca/eng/educators/resources/astronomy/module5/content.asp#5
 A Naked-eye Comet in March 2013: http://www.youtube.com/watch?v=OZlenAvqLCI
 Asteroid 4179 Toutatis: http://echo.jpl.nasa.gov/asteroids/4179_Toutatis/toutatis.html
 What Exploded over Russia? http://science.nasa.gov/science-news/science-at-
nasa/2013/26feb_russianmeteor/

107
Discussion on the Activity
During the discussion of the activity, highlight the similarities and differences
of the two guided by Table 1 found in the Student LM. In addition, mention that
comets and asteroids rotate in their own axes. In addition, mention that while
asteroids usually come from the Asteroid Belt, some may originate from other parts
of the solar system. Tell the class that while a comet or asteroid orbits the Sun, some
parts may break off from the comet or asteroid. These fragments are called
meteoroids. Comets, asteroids, or their fragments come from very distant places
within and beyond the Solar System.
Stress that when a comet or asteroid enters and passes through Earth’s
atmosphere, it will be changed physically and chemically. Usually, the fragments
from space are completely burnt and only cosmic dust reach Earth. But when these
fragments do survive passing through Earth’s atmosphere, the fragments can be as
small as a sand grain or as big as a boulder. The impact releases great amounts of
energy that can damage hundreds of miles from the point of impact. In fact, the
discovery of an impact crater at the Yucatan peninsula in Mexico is being touted by
scientists as the strongest evidence to support the Impact Theory which explains the
extinction of dinosaurs and other species of animals in plants 65 million years ago.
Include in the discussion that an asteroid impact 65 million years ago is being
considered by scientists as the most probable cause of extinction of dinosaurs and
other plants and animals that ended the Cretaceous Period. This was based on an
initial study of sediments in marine layers by Luis and Walter Alvarez (father-and-son
team of geologist).
Emphasize to the class that the scientific community does not just accept
new findings easily. Rather, further studies by different groups of scientists proposing
supportive or competing theories about mass extinction, findings compared, and then
discussed and decided on by an international community of experts just like how the
Alvarez Hypothesis was finally endorsed in March 2010 as the most probable cause
of the mass extinction that killed the dinosaurs and other plants and animals 65
million year ago (refer to the Student LM). Similarly, students should also exhibit the
same scientific attitude of critical thinking and scepticism in face of new or differing
observations, and to openly discuss and validate findings with that of other groups
before arriving at conclusions in class.
Suggested Investigation (for advance sections):
1. Guide the class in identifying possible factors that can affect the shape and size
of an impact crater. Take up each characteristic one at a time.
2. After the class has enumerated several factors that can affect the shape of the
crater, tell each group to choose one factor to investigate (i.e., size of the
meteoroid, angle of contact with Earth’s surface, speed of the approaching
meteoroid).

108
3. Guide each groups in formulating an investigable question based on the factor
they have chosen.
4. Then, instruct the groups to come up with an illustration of their experimental
setups using the materials listed in the activity sheet. Ask each group what
variable or factor they will make the same, and what they will make different.
5. Remind them to make their own data table and label appropriately.
6. Remind the group’s to have at least three setups and conduct three trials for
each.
This activity will allow the students to know the difference among meteor,
meteoroid, and meteorite and how these three are related. By this time, the students
should know the difference between a comet and an asteroid. Review of these
concepts by making the students compare and contrast the characteristics of a
comet and an asteroid.
Teaching Tips
1. Look for three different objects (found in the classroom or anywhere in the school
grounds) that have the approximate size of a meteoroid and a meteorite. You will
use this in helping the students visualizing the size of a meteoroid and a
meteorite.
2. Depending on your assessment of your class’ reading skills, choose to give
Activity 2 as an individual, paired, or group activity.
3. Remind the students that they do not need to memorize the names of the
meteorites and the comet or asteroid source of the meteor showers.
Q1: A meteor is a light phenomenon or a streak of light as observed from Earth
when a meteoroid passes through Earth’s atmosphere.
Q2: A meteoroid is a fragment from a comet, an asteroid, Moon, or even Mars
that orbits around the Sun, following the orbit of its parent or source.
Q3: Meteoroids can come from comets, asteroids, the Moon, and Mars.
Q4: A meteor is observed when a meteoroid passes through Earth’s atmosphere
and burns up in the process.
Q5: When viewed from Earth, a meteor moves fast while a comet moves slow.
Also, a comet is very difficult to see with an unaided eye due to its distance
from Earth. A meteor is more readily seen on a cloudless night.
Q6: Use the following symbols for each:  meteor;  meteoroid; and 
meteorite.
Meteor, meteoroid, and
meteorite: How are they related?
Activity
2

109
The placement of the legends need not be exact but the meteoroid should be
just a little above the atmosphere (white space), the meteor in Earth’s
atmosphere (white space), but the meteorite should be on the crust (line).
Q7: A meteoroid is the space rock fragment before it enters Earth’s atmosphere.
When it enters the said atmosphere and burns up, a light phenomenon is
observed and is called a meteor. When a meteoroid or part of a meteoroid
survives passing through Earth’s atmosphere, the space rock fragment that
lands on Earth’s crust is now called a meteorite.
Q8: A meteor shower is an annual light phenomena characterized by many
meteors appearing in the sky in a short period of time.
Q9: A meteor shower happens when Earth passes through the orbit of a comet
(or an asteroid) where fragments and dust remain in orbit and orbits the Sun
as well while Earth goes around the Sun. Since there are more dust and
fragments, there are more meteoroids that may burn up in Earth’s
atmosphere as Earth passes the orbit of the parent comet or asteroid.
Q10: The meteors in a meteor shower seem to come from one point in the sky
because they are travelling in parallel paths with the same velocity.
Emphasize to the class that a comet or an asteroid may break apart while
orbiting the Sun. When this happens, the fragments from comets or asteroids still
orbit the same path as their mother comet or asteroid. These smaller fragments are
called meteoroids. Use real-life objects to approximate and visualize the size of
meteoroids (some can be as big as an asteroid or as small as a grain of sand).
Stress the concept of a meteor and a meteor shower as light shows or light
phenomena in the sky. Refer to the report on a meteoroid explosion in Russia in
Atmosphere (Earth)
Note: Dimensions are not drawn to scale. Crust
(Earth)



Outer Space

110
February 2013 which was reported as a meteor crashing on Earth; with the class,
correct the terms used in the said report.
Highlight how the scientific community made use of meteorites collected in
Earth, as well as newer studies made on orbiting comets and asteroids in learning
more of Earth’s past, including how past impacts with Earth changed the climate the
planet leading to mass extinctions of plants and animals including the dinosaurs; and
contributed to the variety and abundance of certain rare metals in impact crater’s
area, and the implications of such to astro mining in the near future.
This activity aims to address existing superstitions that the students have or
superstitions that they will discover through library research. Stress to the class that
since the activity is a group work, they must plan a way to make their library
research, online research, and interview with elders effective and efficient. Suggest
that they distribute members to do each of the research tasks. After giving general
instructions, accompany the students to the library. Observe how they work in groups
so that you can give feedback to the group on the following day. They will utilize the
rest of the period to do the research needed. Those who will be doing interviews will
be doing it as homework. The results of their research will be consolidated,
discussed, and finalized on the next day.
Teaching Tips
1. Teach the students how to properly cite references found from different books,
magazines, or journals in the library, as well as how to cite online resources.
2. Teach the students on how to search in the library for books using the card
catalogue (you can ask the school librarian to do the orientation) or how to use
key words in searching for references online (if computers with internet access
are available). For example, key words would include “superstitions +
Philippines + comets”, “comets + superstitions”, etc.
3. Facilitate the presentation of group outputs in such a way that there is a free
exchange of ideas happening in the class. Ask the class why they think these
superstitions are hard to change and why people believe in them despite
scientific evidence that says otherwise.
Do superstitions about comets,
asteroids, and meteors have
scientifc basis?
Activity
3

111
All the answers to the activity will depend on the students’ research. The
rubric below is a guide for assessing their output. You may change the percentages,
add more criterions, or revise the description of the related criterion.
Table 4
Sample Rubrics
Weight/
Percentage
Criterion Description
25% Quality of research All possible sources of information were
exhausted (library, internet, people interviews)
25% Evidence-based
stand
Evidence gathered to support the group’s stand
is well supported by accurate scientific facts
and information (latest or up-to-date
information whenever possible).
25% Impact of proposed
actions
Proposed actions are doable, suited to the
target audience, and effectively lessened the
superstitious beliefs of the target audience.
25% Group work Tasks are well delegated among members;
everyone participated in doing research or
interviewing people; everyone participated and
carried out their task well in implementing the
proposed actions.
Point out to the class that the need for evidence-based stands and arguments
are important in the scientific community to highlight that information we now know
changes as more information come into light after sufficient data gathering, sharing
of data, and discussion of results and inferences. This highlights the nature of
science as being tentative and evidence-based. More so, remind the class that in the
course of addressing the superstitions of other people, they must also exercise
sensitivity towards the religious and cultural background of the people they are trying
to reach.
References
Bely, P. Y., Christian, C., & Roy, J. R. (2010). A question and answer guide to
astronomy. United Kingdom: Cambridge University Press.
Jones, T. & Stofan, E. (2008). Planetology: Unlocking the secrets of the solar
system. U. S. A.: National Geographic Society.
Plait, P. (2002). Meteors, meteoroids, and meteorites: Oh my! The impact of meteors
and asteroids. Bad Astronomy. U. S. A.: John Wiley & Sons, Inc.

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Links
American Meteor Society. (2013). Meteor FAQs. Retrieved from
http://www.amsmeteors.org/meteor-showers/meteor-faq/#1
Burns, P. R. (2009, May 12). Meteors, meteoroids, and meteorites. Retrieved from
http://www.pibburns.com/catastro/meteors.htm
Canadian Space Agency. (2004). Module 5: Comets, meteors, and asteroids.
Retrieved from http://www.asc-
Csa.gc.ca/eng/educators/resources/astronomy/module5/content.asp#5
Lawrence Hall of Science. (2013). Hands-on universe program: Cosmic cataclysms.
Retrieved from http://www.globalsystemsscience.org/studentbooks/acc/ch1
Lunar and Planetary Institute. (2012). About comets. Retrieved from
http://www.lpi.usra.edu/education/explore/comets/background/
Mihos, C. (1997-2006). Asteroids. Retrieved from
http://burro.astr.cwru.edu/stu/asteroid.html
National Aeronautics and Space Administration. (2004). Asteroid 4179 Toutatis.
Retrieved from http://echo.jpl.nasa.gov/asteroids/4179_Toutatis/toutatis.html
National Aeronautics and Space Administration. (2004). What exploded over Russia.
Retrieved from http://science.nasa.gov/science-news/science-at-
nasa/2013/26feb_russianmeteor/
Notkin, G. (2005-2013). Types of meteorites and classification. Retrieved from
http://geology.com/meteorites/meteorite-types-and-classification.shtml
Phillips, T. (2012). Big asteroid tumbles harmlessly pass earth. Retrieved from
http://science.nasa.gov/science-news/science-at-nasa/2012/12dec_toutatis/
The Meteoritical Society. (2002-2012). Meteorites from the Philippines. Retrieved
from Meteoritical Bulletin Database
http://www.lpi.usra.edu/meteor/metbull.php
University of California Regents. (2000). The comet’s tale: Characteristics. Retrieved
from http://cse.ssl.berkeley.edu/segwayed/lessons/cometstale/
frame_characteristics.html
University of California Regents. (2000). The comet’s tale: Orbits. Retrieved from
http://cse.ssl.berkeley.edu/segwayed/lessons/cometstale/frame_orbits.html
University of California Regents. (2000). Asteroid. Retrieved from
http://cse.ssl.berkeley.edu/segwayed/lessons/cometstale/glossary/glossary_6
th_new/asteroid.html

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UNIT 3: Matter
Overview
In Grade 7, the development of ideas about matter began with learning about
common properties of solutions and becoming aware of materials in terms of the
components they are made of—substances, elements, and compounds. These
concepts were encountered by the students in the contexts and life situations that
they were most familiar with. The focus was more on the ‘macro’ view (the tangible
and visible). Such approach is how science concepts should be taught initially. As
students move to Grade 8, they will now delve into what matter is made of and will
go beyond what their eyes can see. In this unit, students will begin to explain some
everyday situations at the sub-microscopic level (atomic level).
There are three modules in this unit: Module 1 is about the Particle Nature of
Matter, Module 2 is about Atoms: Inside Out, and Module 3 is on The Periodic Table
(PT) of the Elements. A variety of visual, multimedia, physical, and conceptual
models to develop students’ understanding will be used to teach about atoms,
molecules, and elements.Many properties of matter as well as its changes in state
can be explained in terms of the arrangement and motion of atoms and molecules. In
the long term, students must grasp the particle model of matter to have a meaningful
understanding of topics in the physical, life, and earth sciences.
While one view of learning science involves the mastery of content
knowledge and science inquiry skills, another view sees students as taking an active
role in building their own knowledge by modifying their existing conceptions of
science ideas through the process of conceptual change. Students need to be
engaged in a process of restructuring their conceptual understanding. The first
important step in doing so is to determine their initial or prior ideas. Research has
shown that students must undergo a conceptual change for them to move to a sub-
microscopic view of matter.
The approach taken in the first module of this unit is for students to observe
more closely different everyday phenomena that will help them gradually understand
the particle model of matter. The activities in Module 1 provide opportunities for
students to think, draw, represent, talk about, and explain ordinary changes of state
such as evaporation, boiling, condensation, melting, and freezing using the particle
model of matter. This strategy enables the teacher to take note of students of
students’ misconceptions and give them the opportunity to deal with them as
teaching goes on.

116
It is hoped that after the first module, students are ready to examine the
structure of the atom and explain how ions are formed In Module 2. They will have a
number of opportunities to appreciate the atom’s structure through the use of
multimedia and other strategies. In Module 3, students will gain a better
understanding of how the periodic table was developed and appreciate the value of
the periodic table as an organizing tool in terms of knowing the properties of the
elements.
Most of the activities in this unit are by themselves formative assessment. As
you collect students’ answers to questions, the results will indicate how far they have
learned and what misconceptions they still hold. At certain portions of the module,
you may use their outputs as part of your summative assessment for one module.

117
THE PARTICLE NATURE
OF MATTER
This module on the Particle Nature of Matter shifts students’ thinking from the
macroscopic view of materials, which was emphasized from Grades 3 to 7 to the
sub-microscopic view of matter.
Key question for this module
Students’ understanding of the particle nature of matter is crucial to how they
will understand much of what is taught in the life, physical, and earth sciences. In
addition, understanding the particle nature of matter helps students explain concepts
such as chemical bonding, chemical reactions, the effects of pressure, temperature,
and volume on gases, changes in state of matter, properties such as density and
compressibility, and topics in life science such as osmosis and diffusion.
What Research Says about Teaching and Learning the Particle
Nature of Matter
Research gives evidence that one of the most difficult concepts for students
to understand is that of the particle nature of matter. One reason why students find
this difficult is that books and instructional materials simply present the idea to
students without helping them develop these concepts. Often, the particle nature of
matter is introduced either as a short paragraph or as a chapter on the atom and the
history of the atom (Harrison & Treagust, 2002). After a brief explanation of the
particle nature of matter, students are not given the opportunity to apply and reapply
these ideas to explain everyday situations. A number of research studies
(Nakhleh,1992; Novick, S.& Nussbaum, J., 1978&1981; Lee, O., Eichinger, D.C.,
Anderson, C.W., Berkheimer, G.D., and Blakeslee, T.D., 1993) have shown that
What is matter made of?
How does the particle model of matter explain some
observed properties and changes in matter?
Unit 3
MODULE
1

118
students at the elementary and high school levels fail to fully understand the
important aspects of the particle model of matter. These aspects of the model
include the following: (1) matter is composed of tiny particles, (2) these particles
have spaces between them, (3) the particles are moving all the time, and (4) the
particles of matter attract each other. Students find these aspects of the model
difficult since these they are more familiar with the observable properties of matter
based on their “sensory perception.”
Students find it difficult to learn the particle nature of matter is because it is
represented at a level which is not observable to them. According to Johnstone
(1991), concepts in chemistry should be learned at different levels of representation.
These are the (1) macroscopic level, which refer to students’ observable everyday
experiences; (2) sub-microscopic or particulate level, which can be used to describe
the structure of atoms and molecules, as well as the movement of particles and
electrons; and (3) symbolic level, which includes the various pictorial
representations, algebraic and computational forms.
However, at the elementary and junior high school levels, students still do not
have a sub-microscopic or particulate view of matter. They think of particles as
smaller parts or pieces of a bigger object (Skamp, 2009). In particular, students
cannot imagine the empty space in matter, including that of gases.Thus, it is very
important for teachers to properly guide students so they can build their ideas about
the sub-microscopic particles, like atoms and molecules.
Building Ideas Through the Use of Models
To help students better understand the particle nature of matter, a number of
researchers (Harrison & Treagust, 1996; Harrison & Treagust 1998; Harrison &
Treagust 2002) have recommended the use of scientific models. Scientific models
(1) are used to think about, explain, and predict scientific phenomena, (2) represent
objects, systems, events or ideas, (3) describe or predict the behavior of objects,
systems, or events, and (4) may be physical, mathematical, or conceptual, such as
the particle nature of matter and the nuclear model of an atom. Therefore, the use of
models help students make sense of their observations and visualize their ideas.
These studies have shown that students still hold misconceptions about the
nature of sub-microscopic particles, like atoms and molecules even if they can
reproduce the diagrams that teachers have taught them. Students fail to realize that
different models represent different aspects of the same situation. Teachers should
keep in mind that students do not see things the way adults do. Thus, students
should be assisted in visualizing ideas by letting them build pictures or models step
by step.

119
In particular, the particle nature of matter is an abstract concept, which can
be understood through the use of models. The teacher can monitor students’ way of
sub-microscopic thinking as the students talk about, draw or illustrate their ideas.
With this approach, it is possible for the teacher to notice misconceptions and deal
with them immediately as the teaching proceeds (Kabapınar, 2009). Teachers need
to develop and build the particle model of matter gradually among students since
understanding the model does not happen in a single step (Department for Children,
Schools & Families, 2008).
It is in this context that this module is developed. Since students have already
been exposed to macroscopic, clearly observable, and concrete situations and
events, as well as hands-on experiences from Grade 3 to Grade 7, it is important that
teachers guide Grade 8 students to a higher level of explaining ideas and concepts.
In this module, the development of the activities is geared towards building
the correct sub-microscopic view about matter. It starts with probing students’ ideas
about matter. This step is important to find out the nature of the students’ initial ideas
and determine what they have understood so far from previous grade levels (Smith,
2001). According to Stavy (1988), there is no point in teaching the particle nature of
matter when students do not know what we mean by matter. In Activity 1, students
are asked to distinguish which is matter from those which are not. They will identify
the common characteristics of matter.
Teaching Tips
1. Let the students do the activity first before initiating a class discussion about
what is and what is not matter.
2. Your objective in Activity 1 is to uncover students’ ideas and reasons for
classifying what is matter and what is not matter. Make sure that they give
their reason for their classification.
3. Research has shown that most students agree that solids and liquids are
matter. But, many students think that gases, heat, and light are not matter.
Which is matter? Which is
not?
Activity
1

120
4. You have to spot areas of agreement and disagreements while students
express their ideas.
5. Encourage students to share their ideas before coming to a consensus that
matter has mass and occupies space.
Table 1. Identifying which is matter
Sample
Is the sample matter?
Reason for your answer
Yes No
Not
sure
sugar granules 
water 
stone 
air inside ball 
leaves 
smoke 
heat 
light 
Q1. The mass of the first 6 samples (sugar granules, water, stone, air inside ball,
leaves, smoke) can be measured.
Q2. The mass of heat and light cannot be measured.
Q3. Not all of the samples occupy space.
Q4. If collected in a container and covered afterwards, it will be observed that
smoke occupies space and its mass can be obtained.

121
Q5. No, heat and light do not have mass. They do not occupy space because these
are not matter. Heat is energy in transit and light is a form of energy.
In Activity 2, students will infer from given situations or observable events
what matter is made of and then explain how these observed situations or events
give evidence that matter is made up of tiny particles.
Based on the study of Novick and Nussbaum (1978), three aspects of the
particle model are least understood by students because these “contradict their
sensory perception of matter.” These aspects include: empty space (or the vacuum
concept), continuous motion of particles, and interaction between particles. Research
has demonstrated that many students cannot visualize space which is “empty.”
When students draw or represent “empty space”, they fill the space with more
particles, dust, or air. In their 1981 study, Novick and Nussbaum showed that most
students even at the initial years of university education” do not retain a uniform
distribution picture of the particles in a gas.” Their study also revealed that senior
high school and university students have difficulty imagining a vacuum or “empty
space” between particles of matter.
Teaching Tips
1. To maximize time, go around each group and interact with the students by
asking questions and clarifications regarding their observations, explanations
and/or drawings.
2. Make sure that their drawings have explanations written beside the
illustration.
3. You do not need to ask all the groups to share their explanations or drawings
to the whole class. What is important is for you to collect the drawings of one
or two representatives of each group.
What is matter made of?
Activity
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Q1. The resulting mixture tastes sweet.
Q2. The mixture is sweet because sugar is still present but we cannot see it
anymore. The sugar particles mixed well with the water particles.
Q3. (Expect students to give a volume less than 70 mL.)
Q4. The volume of the resulting mixture is less than the sum of the volumes of the
unmixed sugar and water.
Q5. The combined volume is less than the sum of 20 mL sugar plus 50 mL water.
This shows that water is made up of tiny particles with spaces between them.
The sugar particles are able to fit into these spaces because the sugar particles
that dissolved in water are very small. These could not even be observed with
the unaided eye.
Q6. The food coloring flowed along the side of the bottle and spread slowly towards
the bottom of the container and began to spread through out the water.
Q7. After one day, the food coloring has totally spread through out the water since
the resulting mixture has a color almost the same as that of the food coloring.
Q8. Since both the food coloring and water are made up of particles, the particles of
food coloring are able to fit into the spaces of the water molecules.
From Activity 2 until Activity 3, you are developing students’ understanding of
the particle model of matter. As previously mentioned, research has shown that
students cannot imagine the empty space in matter, including those in gases. Hence,
they have difficulty understanding compression and expansion of gases.
According to Lee, Eichinger, Anderson, Berkheimer, and Blakeslee (1993),
“students believed that air flows like water from one place to another and, thus, is
unevenly distributed.” When students compressed air in a syringe, some middle
Are the particles of matter
moving? What is between them?
Activity
3

123
school students thought that “air was pushed forward and moved to the opening of
the syringe.”
Poor understanding of the four basic aspects of the particle nature of matter
will affect how students think about changes of state. In this module, you are building
the students’ present understanding of the particle model so that they will form more
connected ideas over time. Your goal is to let the students understand the
importance of using the particle model of matter to explain and predict change of
state when they do Activities 4 to 6. Eventually, they will be able to use the particle
model to explain situations or events they encounter in daily life, specifically various
phase changes.
Teaching Tips
1. Please refer to Teaching Tips numbers 1 to 3 of Activity 2. The same tips
hold true for Activity 3.
2. Emphasize that a gas can be expanded and compressed; it can be added
to or removed from a container with a fixed volume.
3. Make sure that their explanations and/or drawings include the following
aspects of the particle nature of matter:
a. Solids, liquids, and gases are made up of tiny particles which are too
small to observe with the unaided eye.
b. There is nothing between the particles.
c. The particles move and collide with each other and with the walls of
the container.
d. There are forces that act between the particles.
4. At this stage, point out the general differences between a liquid from a
gas.
a. Gases are easily compressed as they have observed Activity 3.
b. Gases can expand to fill up its container.
c. Liquids take the shape of their container but do not expand to fill them
up.
d. Liquids are not as easy to compress as gases because the spaces
between the particles in a liquid are much smaller than in gases.

124
Q1. No, the plunger cannot be pushed all the way through the syringe. (The plunger
can be pushed until the 15-mL level of the syringe and then it goes back near
the 26-27 mL level).
Q2. The plunger of the syringe could be slightly pushed. The springiness of the air
inside the syringe can be felt. This gives a hint about the distance between the
particles of air.
Q3. We cannot push the plunger in the syringe with water inside.
Q4. We were able to push the plunger of the syringe with air in it but the plunger of
the syringe with water in it could not be pushed. We felt the resistance of the
water to being compressed.
Q5. Air, being a gas, can be compressed because there are large spaces between
the particles so the particles can be made to come closer to each other. The
plunger could not be pushed in the syringe with water because water is not as
compressible as air. The particles of liquid water are closer to each other and it
is difficult to push them even closer to each other.
Q6. Yes, water flowed freely as it is poured into another container. Water
maintained its volume and took the shape of the container.
Q7. Water poured on the flat surface of a dinner plate spread out to fill all the space
available.
Q8. When the bottle cap inside the bottle was transferred to the dinner plate by
tilting the bottle, the bottle cap simply slid along the side of the bottle. The
bottle cap retained its shape and volume.
Q9. The salt sample may or may not take the shape of the container depending on
the diameter of the container and the amount of salt used. (But if the container
has a narrow diameter, and there are more salt used, then salt takes the shape
of the container.) The little pieces of salt or sand maintained their shape.
As students construct and revise their models while they discuss with you
and their classmates, they realize that solids, liquids, and gases are made up of tiny
particles too small to see and they have spaces between them. After doing Activities
2 and 3, they will be able to infer that the particles move based on their observation
that the drop of food coloring slowly mixed with water even without being stirred.

125
According to Novick and Nussbaum (1978), the particle model becomes significant to
the students if “several of the aspects are taken together and understood.”
Activity 4 allows the students to use the particle model of matter to explain
evaporation, the change that takes place when particles of a liquid are changed to a
gas. They will observe evaporation in two different situations: in an open container
and in another container which is covered.
Teaching Tips
1. Please refer to Teaching Tips numbers 1 and 3 of Activity 2. The same tips
2. Point out that during evaporation, the water molecules evaporate only from
the surface of the liquid.
3. Students should realize the difference between the open and the closed
containers in terms of how evaporation is taking place. Explain that in the
open container, the molecules of water that evaporate from the surface mix
with the surrounding air and the chance that they will return to the liquid is
very small. All the water molecules will eventually evaporate.
4. In the closed container, the water in the gaseous state (or what we call vapor)
accumulate above the liquid. They cannot escape. Some of these molecules
return to the liquid state. Over time, the amount of vapor increases until the
number of molecules that evaporate is equal to the number of molecules that
go back to the liquid state.
What changes take place when water is
left in an open container? In a closed
container?
Activity
4

126
Q1. The cover of container No. 1 had droplets of water on it.
Q2. There is no more water left on container No. 2. (In some cases, there may be a
very small amount of water left, depending on the area of the room where it
was placed overnight.)
Q3. In container No. 2, the water from the watch glass turned from liquid to gas and
escaped to the air. (Some student may already know about evaporation. So,
they would write, “water evaporated to the air above the liquid water.”
Q4. Yes, it will be different if container No. 2 was heated. In a very short time, most
of the water on the surface of the liquid will turn from liquid to gas because the
higher temperature will cause the particles of water to move much faster and
have more energy to escape from the surface of the liquid.
The study by Vanessa Kind (2004) revealed that many students up to 18
years of age still find it difficult to explain what happens when a gas is heated or
cooled. She found out that students do not realize that particles are constantly
moving. In the study of Novick and Nussbaum (1981), 40% of the 16-year olds
thought that “particles are forced apart” when a gas is heated. Further, Kind (2004)
showed that the idea that the motion of particles decreases when cooled seems to
be harder to understand than the fact that particle motion increases when heated.
Activity 5 will give you the opportunity to observe the extent to which your
students have grasped the different aspects of the particle model of matter. While the
activity is commonplace, the students should be able to explain the phenomena of
boiling and condensation beyond what they could observe with their eyes.
What changes take place when
water is heated or cooled?
Activity
5

127
Teaching Tips
2. Point out that some differences between evaporation and boiling.
a. During evaporation, the water molecules evaporate only from the surface
of the liquid but during boiling, water molecules evaporate both from the
surface and within the liquid.
b. Evaporation can occur even at low or high temperatures, but boiling takes
place at specific temperatures and pressures, depending on the liquid
that is used.
3. A common misconception that might arise in the discussion within the groups
or in class is that the temperature of a liquid increases as it boils. If this
misconception arises, recall what they did in Quarter 1 of Grade 7 or do a
short class demonstration to show that the temperature of a liquid remains
constant when it has reached its boiling point.
Q1. There are bubbles formed at the bottom of the beaker and bubbles in the
boiling water. There is also steam observed above the liquid.
Q2. The bubbles are water in the gaseous state. (It is very common for students to
say that the bubbles formed are air. At the start of the heating process,
however, the tiny bubbles that form are due to the air dissolved in the water.
This is not boiling.)
Q3. The volume of water in the beaker will decrease if water will be kept boiling for
more than 10 minutes because there will be rapid evaporation of water.
Q4. As the water is heated and the temperature of the water rises, the molecules
gain more kinetic energy and they move faster. More molecules have the
energy to overcome the forces of attraction of the neighboring molecules.
These molecules escape to the gaseous phase.
Q5. Students’ drawings will vary. What is important to note is how students
represent and explain the escape of fast-moving molecules of water from the
surface of the liquid to the air. Also, their representation or drawing of water in
the gaseous state should show that the molecules of water are very far apart.

128
Q6. As the water began to cool, droplets formed under the watch glass that covered
the beaker containing hot water. There are also drops of water formed on the
inside wall of the beaker. Some of these drops of water were observed falling
to the water inside the beaker.
Q7. The water droplets at the bottom of the watch glass are the molecules of water
that escape from the liquid and go into the gaseous phase. These water vapor
rise and some molecules touch the glass.
Q8. Students’ drawings will vary. Their illustrations should show that the particles or
molecules representing water in the gaseous state should be very far apart and
as the water begins to cool, the particles should be drawn closer to each other.
Q9. When a gas is cooled, the motion of the particles slows down. If the particles
lose enough energy, their attraction for each other can overcome their motion
and cause them to come closer with one another to become a liquid.
Activity 6 completes the common examples of changes of state observed in
daily life which can be explained by the particle model of matter. After performing
Activities 4 to 6, students should be able to understand that the solids, liquids, and
gases differ because of the arrangement and motion of the particles in each state as
well as the attraction between them. It should also be clear to the students that the
same particles of matter are involved when these changes happen. No new
substances are formed.
Teaching Tips
2. Since this is the last activity for the module, be on your guard that students do
not simply say or define the aspects of the particle model of matter without
supporting their statements with drawings or cartoons. As Liu and Lesniak
(2006) pointed out in their study, teachers must be aware of students’ ideas
about matter.
What changes take place when
ice turns into liquid water?
Activity
6

129
At this stage, you should have bridged the students closer to the more
scientific model of matter. Liu and Lesniak (2006) said that “developing
understanding of matter needs to help students attend to all aspects of the
matter concept and develop meaningful relations among the aspects.”
Q1. After one to five minutes (depending on the room temperature), the ice begins
to turn into a liquid. (Some students may write that “the ice melted.”) When ice,
which is a solid, turns into a liquid, the particles or molecules of solid water
vibrate faster due to the higher temperature in the room compared to the
freezer. Eventually, the particles or molecules break away from their fixed
positions and so they turn to a liquid.
Q2. The liquid will turn into solid when transferred to the freezer.
References
Brady, J.E.,& Senese, F. (2004). Chemistry: Matter and its changes (4th
ed.). River
Frank, D. V., Jones, T.G., Little, J.G., Miaoulis, B., Miller, S., & Pasachoff, J.M.
(2008) California focus on physical science. Boston, Massachusetts: Pearson
Prentice Hall.
Harrison, A.G. &Treagust, D.F. (2002).The particulate nature of matter: Challenges
in understanding the submicroscopic world. In J.K. Gilbert, O.D. Jong, D. F.
Treagust, & J.H. van Driel (Eds.), Chemical Education: Toward research-based
practice (pp 189-212). Dordrecht, The Netherlands:Kluwer.
Harrison, A.G. & Treagust, D.F. (1996).Secondary students’ mental models of atoms
and molecules: Implications for teaching chemistry. Science Education, 80 (5),
509-534.
Johnstone, A. H. (1993). The development of chemistry teaching: A changing
response to changing demand. Journal of Chemical Education, 70(9), 701-705.
Kind, V. (2004). Beyond appearances: students’ misconceptions about basic
chemical ideas (2nd
ed.). Retrieved
fromhttp://www.rsc.org/images/Misconceptions_update_tcm18-188603.pdf

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Krajcik, J. S. (2012). The importance, cautions and future of learning progression
research. In A.C. Alonzo & A.W.Gotwals (Eds.), Learning progressions in
science: Current challenges and future directions (27-36)Rotterdam,
Netherlands: Sense Publishers.
Retrieved from https://www.sensepublishers.com/media/593-learning-
progressions-in-science.pdf.
Lee, O., Eichinger, D.C., Anderson, C. W., Berkheimer, G. D., & Bladeslee, T. D.
(1993). Changing middle school students’ conceptions of matter and molecules.
Journal of Research in Science Teaching, 30 (3), 249-270.
Merritt, J.D., Krajcik, J. & Shwartz, Y. (2008).Development of a learning progression
for the particle model of matter.ICLS’08 Proceedings of the 8th
International
Conference for the learning sciences, International Society of the Learning
Sciences 2, 75-81.Retrievedfromhttp://dl.acm.org/citation.cfm?id=1599881
Nakhleh,M. (1992). Why some students don’t learn chemistry, Journal of Chemical
Education, 69(3), 191-196.
Nakhleh, M., Samarapungavan, A., & Saglam, Y. (2005). Middle school students’
beliefs about matter. Journal of Research in Science Teaching, 42 (5), 581-
612.
Novick, S. & Nussbaum, J. (1978). Junior high school pupils’ understanding of the
particulate nature of matter: An interview study. Science Education, 62 (3),
273-281.
Novick, S. & Nussbaum, J. (1981). Pupils’ understanding of the particulate nature of
matter: A cross-age study. Science Education, 65(2), 187-196.
Skamp, K. (2009). Atoms and molecules in primary science: What are teachers to
do? Aust. J. Ed. Chem., 69, 5-10. Retrieved from
http://www.raci.org.au/sitebuilder/divisions/knowledge/asset/files/38/ausjecissu
e69(pdffile)[1].pdf
United Kingdom. Department for Children, Schools & Families (2008).Using models,
science study guide. Retrieved from
http://www.iteach.ac.uk/LinkClick.aspx?fileticket=wc0DUlOOxMQ%3D&tabid=10
06&mid=7745
Wilbraham, A.C., Staley, D. D., Matta, M.S., & Waterman, E.L. (2007).Chemistry:
Teacher’s edition for California. Boston, Massachusetts: Pearson Prentice Hall.

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What makes up an atom?
How do these components differ from each other?
How are these components arranged inside the atom?
How are atoms different from ions?
How is the atom different from the ion?
ATOMS: INSIDE OUT
In the earlier module, students learned about the particulate nature of matter.
They have learned that elements, the simplest form of matter, are made up of basic
units called atoms. In this module, the students will delve deeper into the atom and
look at its structure. It is imperative that the students recognize that the atomic
structure they are studying is a scientific model. It is not the real thing as no one has
ever seen what the atom really looks like, as pointed out in the Teacher’s Guide for
Unit 3 Module 1. However, several scientists design experiments that may manifest
the composition and structure of the atom which may lead them to propose a model
for the atom. Proposed models are tested further, sometimes by other scientists, to
determine their validity. If new evidence would disprove a model, another model is
proposed. In this module, students will realize that scientific models may evolve and
the one that is currently accepted may still develop as modern scientists continue to
investigate about the atoms.
With the discoveries about the atom that are yet to come, the students can be
enjoined to partake in this exciting possibility. They can start by equipping
themselves with knowledge as they explore the atoms inside out.
Unit 3
MODULE
2

132
Science Ideas
•Atom is regarded as the smallest, basic unit of matter. Even if it is the basic unit of
matter, it is still composed of parts.
•The parts are the electrons (-), protons (+), and neutrons (0).
•An atom has equal number of protons and electrons. This makes the atom neutral.
•Protons and neutrons are relatively heavier than electrons. They compose the
nucleus and collectively called as nucleons. The mass of an atom is mainly
determined by the mass of the nucleus.
•Several models have tried to show how the subatomic particles are arranged in an
atom. Thus far, the accepted model places the protons and neutrons in the center of
the atom; or the so-called, nucleus. Moving rapidly around the nucleus are the
electrons.
•Atomic number, or the number of protons of an atom distinguishes an element from
the others. This number is the same for all atoms of a particular element.
•While the number of protons is fixed for an atom of an element, the number of
neutrons may vary. Atoms having the same number of protons but different number
of neutrons are referred as isotopes. The isotopes are identified through their mass
number which is the sum of the number of protons and the number of neutrons in
an atom.
•Information on the subatomic composition of an element may be represented
through shorthand notations.

133
Matter
Grade 7 scope
may either be
Substances Mixtures
which can be distinguished by their
Grade 8 preceding
module scope
Atom may combine to form Molecule
Macroscopic
Properties
Sub-microscopic composition
explained by their
having the
basic unit,
is almost empty space but is composed of three basic parts,
Protons Neutrons Electrons
Grade 8 scope of
this module
in the massive part of
the atom, called
Nucleus
may not be equal in
number as
equal in number in a neutral atom
may
lose or
gain
forming
Ion
move around the
bound together
differentiate
may
either be
Compounds
Elements
have a
(+) charge
(-) charge
no charge
have
have a
Figure 1. Concept map for atom

134
The students might find it surprising that all objects contain charged particles;
not everything they touch gives them an electric shock. This activity provides
students an “experience” to deduce that even those objects that appear to be
neutral contain charges. In these objects the positive charge equals the negative
charge. To bring in this idea, the students are given this “experience” to remember
that neutral objects may be “charged”.
Teaching Tips
1. Let the students do the activity first before initiating a class discussion.
2. Your objective in Activity 1 is to let students realize that objects contain
charges. This will be the jump-off point of the charged particles that compose
the atoms. Perhaps, after the activity, you can pose a rhetorical question
such as “where do all these charges come from?”. Expectedly, there will be
no way for students to see with their very own eyes these charged particles.
However, the experience they will have in this activity will show that objects
contain charges.
3. You may access http://phet.colorado.edu/en/simulation/balloons* for a
simulation of how charges are transferred between objects. This simulation
also used balloons. You may ask the students the net charge of the balloon
after it was rubbed against their hair. Moreover, ask them about the charges
of their hair and the frame glass.
*Note: Some rights reserved. Please read about the organization’s terms and
conditions on the use of their software. You may access this in
http://phet.colorado.edu/en/about/licensing
4. Please take care of handling the picture frame glass in Procedure 3. In case it
is not possible to monitor each student while performing the activity, it is
advisable to make this part as a class activity. You may prepare one setup for
the whole class. Ask a representative to perform this part of this activity for
the whole class to observe.
“Charge” it to experience!
Activity
1

135
5. This might be the students’ first time to encounter the word, relative. It might
be advisable to find an opportunity in giving them an idea on what relative
means. They will encounter this word several times in the module such as
relative masses, relative charges, size relative to-.
You may include the discussion below when Table 2 is presented to them.
Discussion: You may
notice the word, relative,
as part of the headings in
Table 2. What do you
mean by relative? It simply
means that you have
considered the relation-
ship of something into a
standard. Let us take for
example the three persons
on the image on the right.
Among these three, the
height of the person in the
middle was chosen to be
the standard or the basis
for reference in comparing
the heights. Relative to
that standard height, the
person on the extreme left (facing you) is shorter while the person on the extreme
right is taller. What if the height of the person in the extreme left is the standard or
the basis for comparison? Are the heights of the other two people relatively shorter
or relatively taller? Right, they are relatively taller than the person on the extreme
left.
Take a look at the relative charges in Table 2. Charges are measurements
themselves. You use an instrument to know a measurement value. For example,
you use a ruler to measure the length of an object and report the measured length
in units such as meter. Similarly, an instrument is used to measure charges and
the measured units may be expressed in coulombs. For the electrons, the actual
charge is -1.602 x 10-19
coulombs; while for the protons it is +1.602 x 10-19
coulombs. Now, try to compare those values. What do you notice? How are the
numerical values related? The numerical values are just the same, isn’t it? The
numerical value is 1.602 x 10-19
. With this, can you think why the relative charge of
electron is -1, for proton is +1, and the neutron is 0?

136
Q1. The balloons pushed away each other. They moved toward opposite directions.
Q2. The balloons acquired the same charge since they repelled one another; like
charges repel.
Q3. The balloons moved toward the glass.
Q4. The glass and balloon have different charges since they got attracted with each
other; unlike charges attract.
In this activity, students will be able to visualize through different ways of
representation (bar graph, pie chart, seesaw), the big difference in mass of the
protons and neutrons compared to the electrons. The numbers, alone, especially
expressed in negative exponents might not give them enough idea on the said
difference. This activity will then give them a visual feel of the relative masses of the
subatomic particles. Transforming these values in different ways, including
converting it to number of particles (Q5), may give them a picture of this difference.
Moreover, the process skill of plotting and interpreting graphs are enhanced.
Ultimately, the students will deduce that the electrons do not contribute
significantly to the mass of the entire atom. Having this in mind, they will later on
connect this with the concept of mass number.
Teaching Tips
1. Student mathematical and graphing skills such as working with exponents
and plotting the values may be challenged in this activity. They might need
some help as they go about the activity.
Q1. Electrons
Q2. Neutrons
Q3. Neutrons and Protons
The big difference
Activity
2

137
Q4. The masses of the protons and neutrons are almost the same. (Drawing:
seesaw is just a little lower in the neutron side)
Q5. 1836 electrons
Computation:
no. of electrons (mass of 1 electron) = mass of 1 proton
no. of electrons (9.109 x 10-28
grams) = 1.672 x 10-24
grams
no. of electrons = 1.672 x 10-24
grams / 9.109 x 10-28
grams
no. of electrons = 1836
Q6. Neutrons and protons
In the previous part of the module, students learned about the subatomic
particles that compose the nucleus. They will learn in this activity that the model of
the atom we currently hold true is a product of discoveries of different scientists.
However, the group given the greatest recognition is the team of Rutherford with
their discovery of the nucleus through their alpha scattering experiment. They
bombarded a very thin sheet of gold foil with heavy positively-charged alpha
particles. The observations were surprising! They never thought that there will be a
certain region in the atom that would be “small but terrible”. This very small region of
the atom is where most of the mass and all the positively-charged (+) particles of the
atom are situated. The effect of hitting it with another (+)-charged particle was quite
unexpected! In Rutherford’s words. “It was as if you fired a 15-inch shell at a sheet of
tissue paper and it came back to hit you.”
Teaching Tips
1. Advance preparation for Part A. Cut out different shapes (e.g., triangle, star,
U-shape) as the “mystery objects”.
2. As pointed out in Module 1, models are used to represent things that are
unobservable by the eyes. In this module, the model that the students will
learn about is on the structure of the atom. They will learn some features of
the current model of the atom such as:
Small but terrible
Activity
3

138
a) at the center of the atom is the nucleus which is composed of protons and
neutrons; the nucleus is massive and very small relative to the entire
atom
b) moving rapidly around the nucleus are the electrons; and
c) most of the atom’s volume is just empty space.
3. You may access http://phet.colorado.edu/en/simulation/rutherford-scattering*
for a simulation of Thomson’s plum pudding (raisin bread) model and
Rutherford’s alpha scattering experiment. You may use the plum pudding
(raisin bread) simulation to reinforce your discussion after the students have
finished Part B. Let them finish part C and use this simulation again to add to
your discussion.
4. Students should realize that models may change over time. Emphasize that
models may evolve as new observations are made, much like how
Thomson’s raisin bread model was replaced by Rutherford’s nuclear model.
5. Below is a sample drawing for the schematic representation of the alpha
scattering experiment. The drawing of the student may not be exactly the
same. Important things to note are:
a) Most of the alpha particles were undeflected.
b) Some alpha particles were deflected in an angle.
c) Few alpha particles deflected almost towards back to the source.

139
Part A
Q1. Depends on the sample
Q4. Inside the box, the marble was rolled over and around. There are times that the
marble bumps the object inside the box. This gave helpful clues to infer the
size, shape and location of the “mystery object”.
Part B
Q1. The coins came passing through the pieces of paper.

140
Part C
Q1. It will be repelled causing the positively-charged alpha particle to move at an
angle away from the positively-charged nucleus.
Q2. It will be repelled but the repulsion will be stronger compared to the repulsion
when the positively-charged alpha particle only came close to the positively-
charged nucleus. The alpha particle will be more strongly deflected since it hits
a particle with a bigger mass, the nucleus of the gold atom.
Q3. The nucleus is much tinier than the ones drawn in the diagram; therefore, there
will be more alpha particles that will pass through.
Q4. There is a very small chance of hitting the target (the nucleus) since it is very
tiny.
In this activity, the students will deal with atomic number and mass number.
They will learn that both these numbers tell information about the subatomic
composition of an element. The atomic number, or the number of protons,
distinguishes one element from others. The mass number, or the total number of
protons and neutrons, distinguishes an isotope of a particular element to its other
isotopes. The average mass number of the element’s naturally occurring isotopes
multiplied with their abundance gives the atomic mass of the element. On the other
hand, they will also learn that the number of electrons of an atom may change
resulting in the formation of ions. Depending on the number of electrons, an atom
can be a positive ion (fewer electrons than protons) or a negative ion (more electrons
than protons). Moreover, they will learn to write all of these information in shorthand
notations.
Teaching Tips
1. You may access http://phet.colorado.edu/en/simulation/build-an-atom* to
reinforce the concepts of atomic number, mass number, and ions. This may
provide visual appeal on the inventory of subatomic particles they have done
in Activity 4. Moreover, the visual addition may give the students insights
such as:
What’s in a number?
Activity
4

141
a) only a change in the number protons changes the identity of the element
b) atoms of an element may have different number of neutrons; and the net
charge remains zero
c) ions are formed by the addition or removal of electron/s
d) a positive ion is formed when electrons are removed from an atom and
the number of electrons becomes less than the number of protons while a
negative ion is formed when electrons are added to an atom and the
number of electrons becomes more than the number of protons.
e) electrons do not have anything to do with mass number since their
contribution to the mass of the atom is negligible
f) adding electrons may increase the size of the atom
Also, the students can assess their learning by clicking on the Game tab.
2. You may access http://phet.colorado.edu/en/simulation/isotopes-and-atomic-
mass* to reinforce the differences in atomic mass of the element’s isotopes.
Direct the students to notice that the atomic mass of an element is closest in
value to the mass number of its most abundant isotope.
3. Post-activity Discussion.
a) Q5 and Q6. You may emphasize the difference in the number of neutrons
of the isotopes of an element.
b) Q7. For simplicity and for this grade level only, you may not include mole
in expressing the atomic mass. The mole concept will be dealt in Grade 9.
Also, reinforce the students’ learning from Activity 2, i.e., electron’s mass
is negligible with respect to the entire atom, by asking them the reason

142
why it is only the protons and neutrons that are considered to contribute
to the atomic mass.
c) Procedure 5. Let the students analyze the completed table. Direct them to
realize that:
- the number of neutrons may be different from the number of protons
and electrons
- there is a net charge when there is unequal number of electrons and
protons; in a positive ion (cation) there are less electrons than protons
while in a negative ion (anion) there are more electrons than protons
d) Procedure 6, Shorthand notations. Note that the subscripts which indicate
the atomic number are the same for all the isotopes of iron. They are
isotopes of the same element, iron.
Q1. Phosphorus
Q2. 15 protons
Q3. 13 protons
Q4. Hydrogen
Q5. 6 protons; 6 neutrons
Q6. 6 protons; 7 neutrons
Q7. Mg: 24.30 grams; K: 39.10 grams
Q8. 3 protons
Q9. 4 neutrons
Q10. 2 electrons

143
Table in Activity 4
Shorthand notation for the naturally occurring isotopes of iron, showing mass number
and atomic number
References
Brady, J.E.,& Senese, F. (2004). Chemistry: Matter and its changes (4th
ed.). River
Bucat, R.B. (Ed.). (1984). Elements of chemistry: Earth, air, fire and water, Vol. 2.
Canberra City, A.C.T., Australia.
Elvins, C., Jones, D., Lukins, N., Miskin, J., Ross, B., & Sanders, R. (1990).
Chemistry one: Materials, chemistry in everyday life. Port Melbourne, Australia:
Heinemann Educational Australia.
Hill, J.W. & Kolb, D.K. (1998). Chemistry for changing times (8th
ed.).Upper Saddle
River, NJ: Prentice Hall.
Philippines. Department of Education. (2004).Chemistry: Science and
technology textbook for 3rd
year. (Revised ed.). Quezon City: Author.
Silberberg, M.S. (2007). Principles of General Chemistry. McGraw-Hill: New York
Isotope Element Name # of p+
# of e-
# of n0
Charge
B-6 Boron 5 5 1 0
N-14 Nitrogen 7 7 7 0
F-19 Fluorine 9 10 10 -1
Ne-20 Neon 10 10 10 0
Mg-24 Magnesium 12 10 12 +2
Al-27 Aluminum 13 10 14 +3
Si-28 Silicon 14 14 14 0
S-32 Sulfur 16 16 16 0
K-35 Potassium 19 18 16 +1
Fe26
54
Fe26
56
Fe26
57
Fe26
58

144
Links
Interactive Simulations: http://phet.colorado.edu/
Some rights reserved. Please read about the organization’s terms and conditions
on the use of their software. You may access this in
NISMED’s AgIMat website: http://curriculum.nismed.upd.edu.ph

145
PERIODIC TABLE
OF ELEMENTS
The development of the Periodic Table could be traced back in 1817 with the
work of Johann Dobereiner, a German chemist who formed the triads of elements
with similar properties like the triad of calcium, barium and strontium. In 1863, John
Newlands, an English chemist proposed the Law of Octaves. He based his
classification of elements on the fact that similar properties could be noted for every
eight element in order of increasing atomic masses. Around 1869 two scientists
determined a way to put the elements in order. Lothar Meyer and Dmitri Mendeleev
both came up with periodic tables that showed how elements should be grouped.
Both scientists were teachers living and working in different places. Meyer lived and
worked in Germany while Mendeleev in Russia. Both arranged the elements in order
of increasing atomic mass. Their arrangement made sense since such arrangement
had the properties of elements repeat periodically. Later, in 1914, Henry Moseley, an
English physicist observed that x-ray frequencies emitted by elements could be
correlated better with their atomic numbers. This observation led to the development
of the modern periodic law which states that the properties of elements are periodic
functions of their atomic numbers.
In this module, the first activity is designed with a historical perspective and
will provide students an experience similar to those of the early scientists who
developed the periodic table. They would be able to come up with ideas on how and
why things could be periodically arranged. The information which they would refer to
on the element cards is the kind that Mendeleev and Meyer would have had at their
disposal and will assist them on how the elements would be arranged. The second
activity will make use of the periodic table to predict the reactivity of the metals.
How did the Periodic Table develop?
What information about elements can be obtained from
this organizing tool?
Unit 3
MODULE
3

146
Science Ideas
•The periodic table is a chart containing information about the atoms that make
up all matter.
•Early scientists developed the periodic table by arranging elements in order of
increasing atomic mass.
•The modern periodic table shows elements arranged in order of increasing
atomic numbers.
•A periodic property repeats itself at regular intervals when elements are
arranged according to a common criterion.
• The properties of undiscovered elements can be predicted based on their
position in Mendeleev’s table.
•The modern periodic law states that the properties of elements are a periodic
function of their atomic numbers.
•Elements may be classified into groups. Members of the same group exhibit
similar properties.
•The modern periodic table is divided into groups or families- vertical columns
and periods or series – horizontal rows.
•There are two sets of families: the representative elements and the transition
elements.
•The uses of the different elements are based on their properties.

147
The periodic table was developed as a result of years of painstaking work by
different scientists. Its present form was a result of meticulous and thorough study by
scientists. The first activity provides you an experience similar to those of the early
scientists who developed the periodic table.
Teaching Tips
1. Advance preparation. Print out the element cards found in the appendix.
2. Let students answer the following questions before doing the activity.
a. What is an element? How many different kinds of atom an element is
made of?
b. Define atomic mass of an element.
c. What is the atomic number of an element?
3. Arrange the element cards on the board in one horizontal line and in the
order of increasing atomic mass. Instruct the class to perform Part A for at
least 20 minutes. Make sure that students identify what is recurring property
did they use as basis for moving the elements into groups. They should also
know the operational meaning of periodic to understand the concept of
periodicity. Anticipate that the students may find difficulty in placing the last
two element cards, tellurium (Te) and iodine (I). Let it be. Allow the students
to think this over. You may discuss their experience on this as Q4 is
answered.
4. The table in page 5 shows the expected arrangement of the element cards in
Part A. Assuming that the element cards have been arranged by the class
this way, discuss the table as the whole class answers Q1 to Q4. Expected
answers are found in the succeeding pages.
Discuss with the class their experience in constructing their table of elements.
Perhaps, it was similar to what the early scientists have experienced, in terms
of grouping together elements with similar characteristics in rows and
columns. Tell them also that they were not given the entire element cards,
rather just some of the elements that had been discovered at the time
Mendeleev and Meyer were working on their periodic tables. When
answering Q3, allow them to remember their experience with the cards for Te
& I. Guide them that similar properties have to take precedence over atomic
mass. Discuss that maybe Mendeleev made the same switch or adjustment.
Explain, too, that at present it is known that the atomic numbers, rather than
atomic masses of the elements form a better basis for ordering them in the
Tracking the path and
constructing the Periodic Table
Activity
1

148
periodic table Mendeleev had no way of knowing this since protons had not
yet been discovered during his time. He thought that the masses of iodine
and tellurium may have been measured incorrectly and that eventually better
measurements would show iodine to be heavier than tellurium. In answering
Q4, they may be able to guess that these gaps represent elements not yet
discovered in 1870. Discuss that Mendeleev predicted that elements would
be discovered in the future to fill these gaps. The prediction was realized with
the discovery of gallium by the French chemist Paul-Emile Lecoq de
Boisbaudran in 1875 and of germanium by Clemens Winkler, a German
chemist, in 1886.
5. After telling students these facts, introduce part B. Ask the groups to try to fit
the cards of gallium and germanium in their respective tables. Do the same
with the cards for noble gases.
Part A
Q1. There are 7 families in the table. The noble gases constitute the 8th group but
will be realized after doing Part B.
Q2. The properties of the element and the compounds formed
Q3. Iodine and tellurium broke the trend in terms of properties. The properties are
quite dissimilar with the other elements belonging to the same column or group.
Q4. There are gaps in the family of boron and aluminum and in the family of carbon
and silicon. These gaps might indicate that there were elements not yet
discovered during Meyer’s and Mendeleev’s time.
Part B
Q1. Gaps were filled. Gallium was placed in the family of boron and aluminum while
germanium was placed in the family of carbon and silicon. The noble gases, on
the other hand, were arranged into a new family.
Q2. Our table of elements did not include the transition elements like the modern
periodic table. The table stops at xenon and it is organized by atomic mass
rather than atomic number.
Q3. While tellurium has a higher atomic mass than iodine, iodine has the higher
atomic number. It is the atomic number and not the atomic mass that is the
organizing principle of the periodic table.

151
Q4. The existence of aluminum and silicon gave Mendeleev an idea that gallium and
germanium should also exist. Since Mendeleev did not know about any member
of the noble gas family, he didn’t have an inkling that others might also exist.
Q5. Element 120 would be placed below radium and element 121 would be placed
below actinium.
Q6. The new element would belong to the group or family of carbon, silicon, and
germanium.
This activity allows students to revisit metals. They will look at their chemical property
by comparing the reactivity of some common metals. Reactivity is the ease and
speed with which a metal reacts with other substances. Moreover, they will be
discussing ways to prevent corrosion of metals.
Teaching Tips
1. Do the following before the activity.
a. Using the Periodic Table, identify the portions corresponding to metals,
nonmetals, and inert gases.
b. Tell the students that they will be using aluminum as one of the metals in
this activity. They will examine familiar objects made of aluminum such as
a softdrink can, a disposable plate, heavy-duty aluminum foil, and
aluminum foil. Compare the shape, thickness, and general appearance of
the objects. Let them observe what happens if they bend and unbend
each object.
Based on the properties they have observed, let the students infer and
explain why this metal was used to make each object.
c. Proceed with the discussion of the reactivity or non-reactivity with other
substances.
d. Bring them back to their experience in Grade 7 Acids & Bases. Ask the
students what would happen if some metals like iron will continue to be
reactive with some substances in the environment? Can we stop
reactivity of metals? How?
Metal . . . Metal: How
reactive are you?
Activity
2

152
2. Students will perform the activity in groups and discuss answers to questions.
3. Remind students to be cautious when handling muriatic acid. Ask students to
wash their hands in running water and rub the affected part with baking soda.
4. Guide the students to infer from the Activity Series of Metals that the more
active metal can react with other substances by displacing or replacing a less
reactive element from its compound. The activity series can be used as a
reference to determine a metals’ reactivity.
5. Important Ideas
a) The metals in a group or family in the periodic table have similar
properties and these properties change gradually across the table. The
reactivity of metals tends to decrease from left to right across the periodic
table and increases from top to bottom in a family.
b) The Group 1 metals, from lithium to francium are called the alkali metals.
These metals are so reactive that they are never found as uncombined
elements in nature.
c) Group 2, the alkaline earth metals are not as reactive as the Group 1
metals, but are more reactive than most other metals. Like the metals in
Group 1, they are also never found uncombined in nature.
d) Elements in Group 3 through Group 12 are called the transition metals.
They are less reactive than the metals in Groups 1 and 2.
e) Only some of the elements in Groups 13 and 15 of the periodic table are
metals. These metals are never found uncombined in nature.
f) The 2 rows of elements placed below the main part of the periodic table
are the lanthanide series at the top row and the actinide series, at the
bottom row. Different lanthanides are usually found together in nature and
are always combined with other elements.
6. If there is a shortage of glass graduated cylinder, an empty glass bottle or vial
can be calibrated to 10 mL and will be used as a measuring device.
Q1. Iron, aluminium and zinc reacted with muriatic acid while copper did not.
Q2. Iron, aluminium and zinc, the metals that reacted with muriatic acid (HCl), are
higher than hydrogen in position in the activity series, hence they are reactive.
Copper on the other hand is below hydrogen in the activity series, hence less
reactive. This means that it cannot displace hydrogen.
Q3. The reactivity increases as it goes from top to bottom of the periodic table.

153
Q4. Yes, Group 2 metals followed the same trend for Group 1 metals in terms of
reactivity.
Q5. The reactivity decreases as it goes from left to right of the periodic table.
Q6. a. Na is more reactive than Mg with HCl
b. Al is more reactive than Ag
c. Zn is more reactive than Fe
Q7. When metals react with other substances, the gradual wearing away or
corrosion of a metal results. This may lead to the deterioration of metals.
Q7. Give ways of preventing corrosion of metals.
Q8. There are several ways of preventing corrosion of a metal:
1. Keep air and moisture away from the metal by covering the metal. This is
done by painting, plastic coating, greasing, chromium plating, zinc plating
or galvanizing and tin plating.
2. Fix small pieces of a more reactive metal to its surface.
Table 1.Data for Activity 2
Metal
Observable Reactions with Muriatic Acid
(Check and describe the metal observed )
Violent Slow No Reaction
iron Reacts slowly to form rust;
accompanied by formation
of bubbles due to
formation of hydrogen gas
copper No reaction.
aluminum Reacts vigorously. The
metal tarnishes;
of bubbles due to formation
of hydrogen gas
zinc Reacts vigorously. The
metal tarnishes;
of bubbles due to formation
of hydrogen gas.

154
References
Elvins, C., Jones, D., Lukins, N., Miskin, J., Ross, B., & Sanders, R. (1991).
Chemistry one: Materials, chemistry in everyday life. Port Melbourne,
Australia: Heinemann Educational Australia.
Frank, D., T. Griffith Jones, J. G. Little, B. Miaoulis, S. Miller, & J. M. Pasachoff
(2008). California focus on physical science. Upper Saddle River, New
Jersey: Pearson Prentice Hall.
Hill, G., J. Holman, J. Lazonby, J. Raffan, & D. Waddington (1990).Chemistry, the
salters’ approach.Oxford: Heinemann Educational Books Ltd.
Magno, M. et al. (1995).Science and technology for a better life series
(Chemistry) (2nd
ed). Teachers Manual.Diwa Scholastic Press Inc. Makati,
Philippines.
Magno. M. et al. (1990). Science and technologyIII.Teachers Manual. Raquel
Commercial Press. Philippines.
Magno. M. et al. (1991). Science and technology III. Book Media Press. Philippines.
McDougal Littell (2007). Science focus on physical science. Sacramento,CA:
Houghton Mifflin Company.
Mendoza, E.E. &Religioso, T.F. (1997).Chemistry. Phoenix Publishing House, Inc.
Quezon City.
PASMEP et al. (1991).Teaching resource package-chemistry.
Philippines. UPNISMED (1991).Science and technology textbook III. Quezon City,
Philippines: Instructional Materials Corporation.
Pedregosa, E. F. (1982). Secondary science for learning and living 3 - Chemistry.
Quezon City, Philippines: Phoenix Press, Inc.
The American Chemical Society (1988).Chemistry in the community. Dubuque, Iowa:
Kendall/Hunt Publishing Company.
The Collins Paperback English Dictionary (1986). William Collins Sons & Co. Ltd.
Great Britain.
Links
http://www.slideshare.net/AmrHassaan/patterns-of-reactivity
http://amrita.olabs.co.in/?sub=73&brch=3&sim=59&cnt=1
2008 Chemical Heritage
Foundation.hhtp://www.gofoster.com/downloads/twe/chap06.pdf.
http://www.google.com.ph/search?q=Mark+Buchanan+Periodic+Table

155
Appendix: Element Cards for Activity 1 (you can make this bigger)
Part A
H
Hydrogen
Atomic Mass: 1.008
Description: odourless gas, very
flammable
Compounds: H2O, HCl
Li
Lithium
Atomic Mass: 6.941
Description: soft gray metal, reacts
with
water
Compounds: Li2O, LiCl
Be
Beryllium
Atomic Mass: 9.012
Description: gray metal
Compounds: BeO, BeCl2
B
Boron
Atomic Mass: 10.81
Description: gray metalloid,
semiconductor
Compounds: B2O3, BCl3

156
C
Carbon
Atomic Mass: 12.01
Description: black solid (graphite)
or transparent crystal (diamond)
Compounds: CO2, CCl4
N
Nitrogen
Atomic Mass: 14.01
Description: odorless gas, rather
unreactive
Compounds: NH3, NCl3
O
Oxygen
Atomic Mass: 16.00
Description: odorless gas, very
reactive
Compounds: H2O
F
Fluorine
Atomic Mass: 19.00
Description: yellowish gas, extremely
reactive
Compounds: HF, NaF, CaF2

157
Na
Sodium
Atomic Mass: 22.99
vigorously with water
Compounds: Na2O, NaCl
Mg
Magnesium
Atomic Mass: 24.31
Description: gray metal, flammable
Compounds: MgCl2, MgO
Al
Aluminum
Atomic Mass: 26.98
Description: silvery metal
Compounds: AlCl3, Al2O3
Si
Silicon
Atomic Mass: 28.09
semiconductor
Compounds: SiCl4, SiO2

158
P
Phosphorus
Atomic Mass: 30.97
Description: white, red, or black,
spontaneously
flammable Compounds: PH3, PCl3,
PCl5
S
Sulfur
Atomic Mass: 32.07
Description: yellow solid powder
Compounds: H2S, SCl2
Cl
Chlorine
Atomic Mass: 35.45
Description: greenish gas, extremely
reactive
Compounds: HCl, NaCl, CaCl2
K
Potassium
Atomic Mass: 39.10
Description: softgray metal, reacts
violently with water
Compounds: K2O, KCl

159
Ca
Calcium
Atomic Mass: 40.08
Description: hard silvery metal,
flammable
Compounds: CaCl2, CaO
As
Arsenic
Atomic Mass: 74.92
Description: gray metalloid
Compounds: AsH3, AsCl3, AsCl5
Se
Selenium
Atomic Mass: 78.96
Description: gray or red solid
Compounds: H2Se, SeCl2
Br
Bromine
Atomic Mass: 79.90
Description: red-orange liquid, very
reactive
Compounds: HBr, NaBr, CaBr2

160
Rb
Rubidium
Atomic Mass: 85.47
violently with water
Compounds: Rb2O, RbCl
Sr
Srontium
Atomic Mass: 87.62
Description: soft silvery metal
Compounds: SrCl2, SrO
In
Indium
Atomic Mass: 114.8
Description: soft silvery metal
Compounds: InCl3, In2O3
Sn
Tin
Atomic Mass: 118.7
Description: silvery- white metal
Compounds: SnO2, SnCl4

161
Sb
Antimony
Atomic Mass: 121.8
Description: bluish- white metalloid,
semiconductor
Compounds: SbH3, SbCl3, SbCl5
Te
Tellurium
Atomic Mass: 127.6
Description: silvery-white metalloid,
Semiconductor
Compounds: H2Te, TeCl2
I
Iodine
Atomic Mass: 126.9
Description: dark-purple solid,
reactive
Compounds: HI, NaI, CaI2

162
Element Cards for Part B
Ge
Germanium
Atomic Mass: 72.59
semiconductor
Compounds: GeO2, GeCl4
Ga
Gallium
Atomic Mass: 69.72
Description: silvery metal, melts at
just
above room temperature
Compounds: GaCl3, Ga2O3
He
Helium
Atomic Mass: 4.003
unreactive
Compounds: none known
Ne
Neon
Atomic Mass: 20.18
unreactive

163
Ar
Argon
Atomic Mass: 39.95
unreactive
Kr
Krypton
Atomic Mass: 83.80
unreactive
Compounds: KrF2
Xe
Xenon
Atomic Mass: 131.3
unreactive
Compounds: XeF6, XeF4

165
UNIT 4
Living Things and Their
Environment

167
UNIT 4: Living Things and Their Environment
Overview
Science is about asking questions and looking for answers.
Each of the five modules on Living Things and Their Environment for Grade 8
starts with questions that guide students in their journey of constructing the big ideas
through activities that are interspersed in the modules. The students are provided
with opportunities to develop the inquiry skills as well as their critical thinking,
problem solving, and communication skills.
There are five modules in this quarter:
Module 1: Biodiversity
Module 2: Interactions
Module 3: The Digestive System
Module 4: Nutrition and Wellness
Module 5: Cellular Reproduction and Genetics
.
Module 1 starts with the big picture - the diversity of organisms in various
ecosystems. Module 2 follows which zeros in energy-matter interconversion.
Organisms then need to break down the complex molecules during digestion
(Module 3) to yield energy that leads to health and wellness (Module 4). The
nutrients takes in by organisms will provide the energy for metabolic processes such
as cellular reproduction (Module 5).
Activities in the Learning Materials are designed to help students connect the
concepts and help them construct the big ideas. Some of the activities may be
performed as groupwork while others may be performed individually. It is strongly
urged that students read the activities before performing them. It is also important
that the students take note of the safety measures.
In the course of using these materials, it is important to engage in effective
classroom discussions. These discussions provide students the necessary scaffolds
to make connections and deepen their understanding of the concepts. These
discussions also provide formative assessment opportunities. Feedback gained from
these formative assessment opportunities will provide the essential data to determine
the succeeding strategies that may be employed to reach the desired learning goals.
Maintaining students’ curiosity about the world requires making them
confident that they can use the methods of inquiry to find answers to their questions.
The K to 12 curriculum spirals and increases in difficulty at each grade level so as to
provide challenges appropriate to the students’ age. As they acquire the tools and
habits of inquiry, they would develop into effective and productive citizens of the 21st
century.

169
BIODIVERSITY
The module will enhance what students already know about organisms found
in almost all places in the world. It will initially bring to mind in students what have
been previously learned in the lower grades, and connect these to what they are
going to study in Grade 8.
This module will introduce students to the system by which scientists have
classified and named organisms for an organized and orderly keeping of information
about them. It will let students explore the similarities and differences of the various
groups of organisms and their representative examples. Through the module,
students will know more of the uses and harm these organisms may bring to
humans, other organisms and the environment.
Activity 1 will make students see that people from different places may call a
particular organism with different names. Thus, it will help them recognize the need
to classify and name them to avoid confusion.
Activity 2 will give students the opportunity to see and identify bacteria used
in making food. At the same time it will make them adept in using the microscope.
Activity 3 will familiarize students with the life cycle of an insect that spread
dengue. It will further help them develop practices that minimize the occurrence of
this deadly disease.
After students survey the different groups of organisms, students will analyze
situations which will enable them to realize the advantages of high over low
biodiversity in Activity 4. Activity 5 will engage students in an activity towards the
protection and conservation of their community’s biodiversity.
The discussions, thought and developmental questions, and activities, will
help students answer the key questions in the module. In addition, this should
encourage them to take seriously what they have learned and will still learn about
biodiversity. Hopefully, learning about the topic will culminate in students’ realization
of the importance of biodiversity in their lives and participate actively in protecting
and conserving it.
Unit 4
MODULE
1

170
Have students read page 1 of the module. Then, ask them to recall what they
have learned in Grade 7 about fungi and algae. You may need to pose questions
like: Are fungi or seaweeds/algae also plants? Are birds animals? Why do you say
so? Accept their answers and tell them they will be able to answer these and other
questions as they discover more about organisms on Earth through the module.
Activity 1 can be done by groups (8 groups per class) for convenience in
procuring pictures of different organisms. Animal pictures can be pasted on colored
paper as this will be more attractive to students.
Advanced Preparation
Gather pictures of any four of the following organisms. Paste each picture on
a piece of paper. Prepare pictures according to the number of groups in your class.
Shark Hibiscus (gumamela)
Dove Coleus (mayana)
Periwinkle (tsitsirika) Turmeric (Luyang Dilaw)
Eucheuma (gozo) Lagundi
Green algae: (lato or ar-arusep) Sambong
What’s in a name?
Activity
1
Why is biodiversity important?
What human activities destroy or endanger the existence of rate and
economically important species?

171
Teaching Tips
1. Two days before Activity 1 you may suggest to students to communicate with
relatives and friends in other places (e.g., in other islands within the country)
through text or email on how birds, shark, or green algae (lato/ar-arusep) are
called in their area.
2. During the activity, tell students to start with the name used for an organism
in their own locality. Accept all other names given by different students to a
particular organism. Inform them that there’s no need yet to come to a
consensus how these organisms are to be called.
3. To save on time, you may request only particular groups to present their
outputs. After the activity, discuss with the students how these organisms are
named in different places in case they will not be able to get information from
other areas in the country:
BIRD (as a group): Ibon (Tag.), Pispis (P. Bis.), Langgam (C. Bis.),
Mammanu (Ibanag)
SHARK
Common/Local Names: Pating (Tag), Bagis (Bis., P. Bis), Iho (Surigao),
ihotiqui (Bohol)
DOVE
Common/local Names: Kalapati (Tag), Pating (P. Bis.)
HIBISCUS
Common/Local Names: Gumamela (Tag), Kayanga (Ilokano, Bik.),
Tapulanga (Negros)
COLEUS:
Common/Local Names: Mayana/Malaina (Tag.)
Lampunaya/Lapunaya/Daponaya (Bis.), Saimayu
(Sulu)
PERIWINKLE
Common/Local Names: Tsitsirika /Atay-bia/Amnias (Tag.), Lubitos (Ivan.),
Sirsirika (Bik.), Pinggan-pinggan(P. Bis.)
GREEN ALGAE: Caulerpa lentillifera or C. racemosa
Common/Local Names: Ar-arusep (Ilokano), Gulaman/Lato (Bis.)
TURMERIC: Curcuma longa Linn.
Common/Local Names: Luyang Dilaw/Dilaw(Tag.), Kulyaw(Ilk.),
Kalawag(Mbo., Bis.), Salampawyan(Bag.)
BLUMEA CAMPHOR
Common/Local Names: Sambong(Tag .), Subsob/Subosob(Ilk), Alimon

172
Alibum/Alibhon (P. Bis.), Kaliban/Kalibura (Tagb.), Dalapot (C. Bis.)
FIVE-LEAVED CHASTE TREE
Common/Local Names: Lagundi (Tag., Ibn., Bik., P. Bis.), Dangla/Limo-Limo
(Ilk.), Dagtan (If.)
EUCHEUMA
Common/Local Names: Gozo (Tag.)
4. Let students proceed with the topics contained in the module clarifying points
which they may not understand or have questions. Discuss the inclusion of
the three-domain classification system. You may need to assist them in
analyzing Table 1 or in answering Questions 4 to 7. Students may wonder
why scientific names are in the Latin language. Explain that Latin is an
unchanging language. Mention that the genus-species name tells something
about what the species is, where it is from and who discovered it. Mention
that scientific names are sometimes written with an incomplete genus name
like E. coli.
KINGDOM ARCHAEBACTERIA
Electron micrographs (Figures 1 and 2) are pictures of things and organisms
observed using the electron microscope.
The cell walls of halophiles contain the pigment carotenoids which are yellow
and orange in color. This accounts for such colors of salt ponds where they are
present in large numbers. This can be observed in certain areas in Bulacan,
Pangasinan, Mindoro Occidental, Davao, and Misamis Oriental where salt is
produced. Encourage students to use the internet or library books to be able to
answer Q9.
KINGDOM EUBACTERIA
Spirilla may occur in three forms, namely spirillum, vibrio and spirochete.
Spirillum is thick, rigid and spiral shown in Figure 3 in the module. Vibrio is curved or
comma-shaped while a spirochete is thin, flexible, and spiral.
In areas where White cheese (kesong puti) is produced, local people use the
term ”starter”. It is rennet or coagulant which contains the lactic acid bacterium.
Rennet is added to fresh unpasteurized milk of cow, carabao or goat to produce
kesong puti.
Several strains of Lactobacillus are added to milk during the production of
yogurt. These include Lactobacillus acidophilus, Lactobacillus caseii and
Lactobacillus reutri. Bifidum bacteria, such as Bifidobacterium animalis and
Bifidobacterium lactis, are also used in making yogurt.

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Advanced Preparation
Two or three days before the activity, procure plain yogurt without flavour
from grocery stores or supermarkets and store in the refrigerator. Request methylene
blue from your laboratory technician or get from a scientific supply store ahead of the
class. To dilute yogurt, add two teaspoons of water to one-fourth (1/4) teaspoon of
yogurt. Prepare this just immediately before students do the activity.
Teaching Tips
1. Ask students if they have any idea what fermented foods or drinks are.
According to their response, you may mention that these are made using
bacteria. Ask for examples that they might know and the availability of these
in their area. In places like Sta. Cruz and Los Baños, Laguna, Bulacan,
Isabela, Nueva Ecija and Cagayan Valley, “kesong puti” is made. You may
mention other products like yogurt, Yakult, cheese and most recently
Probiotic drinks.
2. Activitiy 2 is a good activity for students to do for schools with microscopes.
You can review students on the proper way of using the microscope, if
needed, especially if they have not done it in Grade 7. Thoroughly washed
droppers from infant medicines can be used if no laboratory droppers are
available.
3. If you still have time or if you have advanced students in the class, you can
also let them do the alternate activity below using fermented milk like Yakult
or any Probiotic drinks available in your locality. For Probiotic drinks use the
unflavored one.
3a. For areas where yogurt is not available, any fermented milk (as
mentioned above) can be used. You must be aware that this is popular
with kids. Introduce the use of bacteria in making yogurt and fermented
milk. Tell them that they will do an activity to observe bacteria in
fermented milk using the microscope. Give the following procedure for
students to do.
How do bacteria in yogurt look
like?
Activity
2

174
Materials Needed:
dropper cover slip
glass slide fermented milk
methylene blue microscope
Procedure:
1. Place a drop of fermented milk on a slide.
2. Add a drop of methylene blue and cover with a cover slip.
Q1. What is the purpose of adding methylene blue to the specimen?
3. Observe under the LPO and HPO of the microscope.
Q2. Describe what you see under the HPO.
Q3. What is the name of the bacteria involved in making this fermented milk drink?
Teaching Tips
1. Questions may arise regarding probiotic drinks. Probiotics refer to
microorganisms that naturally live in the intestinal tract. They are “friendly
bacteria” and believed to strengthen the immune system. It is helps in the
overall maintenance of good health. Explain that fermented milk/probiotic
drinks are also made by adding beneficial bacteria to skimmed milk. The
process involved is the same as that in making yogurt. It occurs because
bacteria break down substances into desirable products like food or drink. Tell
students that they will understand more of the fermentation process in Grade 9.
2. For students to answer Q3, show them the container of the fermented/probiotic
drink you used. Sometimes the bacteria used is in the list of ingredients found
in the plastic package for 6 bottles of the fermented milk. You can ask from the
saleslady this plastic cover to show to your students. Fermented drinks in the
market may use Lactobacillus casei Shirota strain or Lactobacillus paracasei. A
bacterial strain is a subgroup of a species having particular characteristics
developed by breeders.
How do bacteria in fermented
milk look like?
Activity

175
Answers to Questions in the Alternate Activity:
Q1. For clearer observation of the specimen.
Q2. Possible answers: Rodlike/cylindrical/long structures can be seen
Q3. It depends on the fermented milk used: Lactobacillus paracasei (in probiotics);
Lactobacillus casei Shirota strain (in Yakult)
In case your school does not have microscopes, show the following pictures
of Lactobacillus bulgaricus and Streptococcus thermophilus as seen under the
compound microscope.
Lactobacillus bulgaricus
Bacillus thuringiensis protein crystals have been developed as an effective
biopesticide in tablet and powder form. It can be sprayed to crops to control corn
borers and diamond backmoth. It is also used to regulate increase in population of
mosquitoes carrying disease-causing organisms.
Some bacterial cells are rich in protein and are utilized as alternative sources of
food. They are cultured in the laboratory as Single Cell Proteins(SCP). SCP can be
mixed with a food base to add protein for cattle diet.
Whether in urban or rural areas those who waded in floodwaters or mud or
stagnant waterlike farmers, veterinarians, pet shop owners and sewage workers are
at risk of contacting leptospirosis. This also includes people who are into camping,
hiking, rafting, canoeing. These people can swallow contaminated food or water and
through contact with broken skin or with mucosal surfaces of the eyes or nose.
Warn students of the danger of wading or playing in floodwaters especially if
they have cuts in the skin. If it cannot be avoided, remind them to thoroughly wash
hands or shower with soap. Leptospira bacteria are killed by soap, disinfectants, and
drying. They should use footwear especially when walking in mud or moist soil. It is
also safe to wear gloves while gardening. Feeding raw offal to dogs must be
avoided. Most importantly, homes and surroundings must be clean. No food sources
must be lying around uncovered so rats can be controlled.
Streptococcus thermophilus x 1000

176
Anthrax is endemic in the Philippines. It can be treated when detected early.
Students should help people understand about the danger of eating “double dead
meat.” They should be on the look-out for reports in the news on anthrax cases as
they provide excellent real-world connection and resources for learning more about
the disease-causing bacteria. Encourage them to consult the barangay health
officers on this matter.
Protists
Some books also refer to the group as Kingdom Protoctista. Chlorophyll in
algae can be masked, thus, other than green algae, there are golden, brown and red
ones. Caulerpa lentillifera is eaten as salad with tomatoes and onion. Clarify that
seaweed as a term applied to Caulerpa and other green algae can mislead people
and mistake it for a plant. Remind students to correct this misconception.
Alginate, the brown powder form of alginic acid, is naturally present in other
brown algae. It is used as stabilizing, thickening or gel-forming agents in ice cream,
candy, toothpaste, and cream cosmetics. Iodine can also be found in brown algae.
Carageenan, a complex carbohydrate from red algae, is used as a suspending
agent in foods, medicines, and cosmetics. It is also a filtering agent in beverages.
Microbiologists use agar as a solidifying agent in the growth medium for
microorganisms and plant tissue culture.
If a prepared slide of euglena is available in your school, have students
view it under the microscope. You can get your specimen from an aquarium or pond
water.
Humans develop malaria when infected with any of the protozoan parasites
from the genus Plasmodium. The four species include: Plasmodium falciparum,
Plasmodium vivax, Plasmodium ovale, and Plasmodium malaria.
Fungi
Certain fungi cause wilting of tomato, papaya, corn and banana. Fungi can also
live together with a single-cell alga forming a lichen.
The figure below shows the structure of a poisonous mushroom. Students
must be reminded of not just eating any kind of mushroom they find in the woods. A
poisonous mushroom has a death cup, white spores, and a ring on the stalk. It
contains amatoxin, a deadly substance which when ingested damages the kidney
and the liver.

177
(Adapted from: Philippines. Department of Education. (2009). Science and Technology II.
Textbook (Rev. ed.). Pasig City: Instructional Materials Development Corporation. p. 266.)
Yeasts are also utilized as SCP.
THE PLANT KINGDOM
As students start to study the plant group, discover if there are still students
who think that all plants are colored green and that green algae are plants. Clarify
that pigments can mask the green color of chlorophyll.
Clarify the term “lumot.” In the Philippines it is applied to algae, cyanobacteria
and mosses. Students should be able at least to differentiate one from the other by
Grade 8.
remnants of
universal veil
cap
gills
ring
stalk
death cup

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Vascular Plants Tracheophytes
Photo by: Alvin J. Encarnacion Photo Courtesy of Michael Anthony B. Mantala
Asplenium nidus bird’s nest Azolla sp.
Start with how ferns are called in your locality. Show pictures of other fern
examples. Or you can show them some species planted in flower pots that may be
found in your school.
The giant fern of the genus Angiopteris (Figure 15a) in the student module
has grown to about 206 centimeters from the base to the highest point of a leaf. In
answering Q31, they should be able to see the height of Angiopteris almost as high
as the first floor of the building.
Azolla can be cultured so that it will be readily available for use in science
classes. The places you can ask about how and where you can get the plants are
the Department of Agriculture offices in your locality, commercial plant gardens, pet
shops, aquarium stores and the UP NISMED website. Here are the materials you
need and the procedure in raising and maintaining an azolla culture:
In an artificial pond, medium sized-basin or pail, put about 2 inches of loam
soil. Add water from an existing aquarium or pond, creek, river, artesian well or
faucet. Add a handful or a few azolla plants and if a pail or basin is used, place in a
shady area. You may stir the soil from time to time for the nutrients to be easily
absorbed by the plants. These can be left to grow and may reproduce fast and can
soon fill up your whole container or pond. During hot days, their leaves may turn
brown or red but can recover during the rainy or cooler season. You can mention
that azolla is also used as food for tilapia.
Other members of the spore-reproducing plants include the whisk ferns, club
mosses and horsetails.
Athyrium esculentum (Retz.) Copel or Diplazum esculentum Retz. called
“pako” is an edible fern. Some eat them raw as salad or steamed with tomatoes.
Dried nito stems are good sources of fiber and are made into handicraft items.

179
Gymnosperms
If you or your school has internet connection, look for images of Welwitschia
at darkroastedblend.com., Dark Roasted Blend: The Strangest Plant on Earth.
Gymnospersms are excellent sources of timber. The bark of pine trees yield
tannin used in tanning animal skins in producing leather. Tannin is also used to make
ink.
Angiosperms
Angiosperms are plants that belong to Phylum Anthophyta. Water plants like
Quiapo, water lily, duckweed, water hyacinth Hydrilla and Vallisneria which grow in
freshwater habitats may need to be introduced to students. Water hyacinth, is often
mistaken as water lily. Water hyacinths have green heart-shaped leaves, bladders
and smaller violet flowers. It also serves as a depollutant, being able to absorb
pollutants in water. In salt waters, seagrasses like the eel grass are found in coastal
areas. Students will see in the next module that aquatic plants play an important role
in food chains.
Have students recall from the earlier grades about aerial plants they know.
Add that the endemic orchid Waling-waling is an endangered species. There is also
a move in congress to make it the second national flower.
An activity or project about medicinal plants can be done by students in this
topic. It will make students aware of the plants in their locality that may be used in
preventing or curing particular diseases.
Harmful Plants
People sometimes forget the importance of weeding. Remind students of the
bad effects of competition for nutrients between weeds and economically important
crops.
Some plants harm animals. Young sorghum leaves contain a toxic substance
that can cause cyanide poisoning. Others like Kantutai/coronitas/baho-baho, and
Hantalakaw/malasili contain chemicals that can be fatal to animals. Morning glory is
also host to the snout beetle (sweet potato weevil) that greatly lessen sweet potato
harvest.
Dieffenbachia maculata (dumbcane), an ornamental house and garden plant,
can be dangerous to children. The leaves and stem with its bitter and poisonous
juice burns the mouth. This causes swelling of the tongue that can affect speech and
block the air passage that may lead to death.
Many cases of tuba-tuba poisoning which led to death of some have been
reported in several areas in the country. Give warning to students about eating any
part of unfamiliar plants.

180
THE ANIMAL KINGDOM
To start the discussion on animals have students recall what they learned
about them in the lower grades. The first invertebrate that students will study are
members of Phylum Porifera, the sponges, also called pore-bearing animals ( from
porus meaning “pore,” and fere meaning “to bear” ).
Cnidarians
Most members of Phylum Cnidaria live in salt waters. Adult corals, sea
anemone and the freshwater hydra live attached to solid materials. Jellyfishes differ
from them as the young are attached but become free-swimming adults. Hydra may
be observed under the microscope using water from bottom portion of ponds or
aquarium.
Encourage students to open internet links for more information about corals.
Mention that coral reefs once damaged take a long time to restore. Bring up
incidents of oil spills in Guimaras, General Santos/Sarangani areas and other places
and the latest damage to the Tubbataha reefs. Discuss the destruction of coral reefs
in relation to fish stock decline resulting to less fish catch, increase in fish prices, less
food supply and economic effects to fishermen.
Several cases of box jelly fish attacks and even deaths in the Philippines
have been reported in the news and feature shows on TV. The sting cause itchiness
and leave severe marks in the body. Warn students to be cautious while swimming in
beaches. If stung by jelly fish, wet cotton with vinegar and place in the affected area.
Ask for suggestions of ways to protect coral reefs.
Flatworms
Flatworms belong to Phylum Platyhelminthes (in Greek platys means flat,
helmins means worm). Encourage students to find out if their towns have
slaughterhouses where beef and pork meats are strictly checked for the presence of
tapeworm cyts. Livestock slaughtered by local people in their homes must be
checked too.
Roundworms
Roundworms such as pinworms and Ascaris are notorious parasites in
children. Hygienic practices are important to avoid being parasitized by these worms.
Young ipi-ipil seeds are usually eaten to expel these worms.
Segmented Worms
Emphasize the role of earthworms in agriculture and of leeches in medicine.
Care, however, must be taken by farmers or researchers in muddy fields so as not to
be victims of the blood-sucking leeches.

181
Mollusks
Point out the thin and flexible skeleton of squids and the white “cuttlefish
bone” usually fed to birds to add calcium to their diet.
A lot of mollusks are used as food by humans and also by other animals.
Many shells are collected for ornaments while others produce pearls.
The marine seashell Turris dollyae (synonymous to Turris
crispa), present in the Philippines and Queensland, Australia was
found to have medicinal value. Dr. Baldomero M. Olivera, its
discoverer, has named it after Dr. Dolores (Dolly) Hernandez, in
honor of her outstanding contributions to Philippine Science
Education. Dr. Olivera is a Professor of Biology at the University of
Utah.
Overcollection of mollusks for food as well as pollution caused
by pesticides used in farming that have reached bodies of water have
killed some mollusks have caused their populations to decline.
Echinoderms
The sea star is what was previously referred to as the “starfish.”
Point out that spines of the sea urchin are long while those of the
sand dollar are short as shown below.
(Source: Philippines. Department of Education. (2009). Science and Technology II. Textbook
(Rev. ed.). Pasig City: Instructional Materials Development Corporation. p. 293).
Photo:CourtesyofDr.BaldomeroM.Olivera

182
Arthropods
Students usually mistake spiders as insects. Point out the differences
between insects and arachnids, specifically, the number of body sections and legs.
They should also be able to distinguish a centipede from a millipede as they may be
bitten by a centipede which is painful and with venom.
Aedes aegypti is the principal carrier (vector) of the virus causing dengue.
The disease is endemic to the Philippines being a sub-tropical country. The activity
will help students understand the life cycle of this insect so occurrence of dengue
can be controlled. Point out that research has found out that young people are at
greater risk of getting sick with the disease because of their lifestyle, that is, wearing
of shorts and sleeveless shirts or blouses and staying in cool dark places.
Teaching Tips
1. In studying the life cycle of A. aegypti, students should take note of what
happens in each stage for them to be able to answer the questions.
2. In answering Q52, they should take note of the white spots, number of body
sections, wings, antenna and legs. For Q54, they must think of any place
where nonflowing and clean water exists.
3. Ask students what larva of mosquitoes are called in the locality. In other
places, they are called ”waya-waya.”
4. Other questions that may be asked of students include: How many stages
does Aedes aegypti go through in its life cycle; how would you describe a
pupa; in which stage does a young mosquito stop eating and which stage/s
is/are easy to destroy or eliminate?
Emphasize that at present there is still no cure nor vaccines for dengue. A
person may also get sick of the disease four times in his/her lifetime. The reason is
there are four strains of the virus that cause dengue. Remember, the next attack by
another strain is more critical. When a person is sick with dengue they are just given
medicines to relieve the symptoms and prevent complications brought by the
disease. Early detection is important in the recovery of dengue patients. When there
is sudden onset of fever that lasts for two days, extreme body and joint pains and
chills or rashes are observed, the patient should immediately be examined by the
doctor.
What can you do to prevent
dengue?
Activity
3

183
Methods to prevent spread of the disease are: 1) control of the vector, that is,
preventing reproduction of the mosquito by removing breeding places, 2) avoiding
mosquito bites by using mosquito nets or installing screens in windows and door, 3)
using safe repellants, trapping and killing larvae and 4) employing biocontrol by
introducing predators of mosquitoes such as dragonflies. Have students recall the
use of Bacillus thuringiensis as microbial pesticide. Mention that it is also applied to
breeding places of mosquitoes that spread diseases.
The Department of Science and Technology- Industrial Technology
Development Institute (DOST-ITDI) has developed an Aedes Mosquito Ovi/Larvicidal
Trap System which is a safe and cheap way of controlling mosquito populations. For
details please visit the following websites: www.science .ph;
www.dengueoltrappcti.com; youtube.com- type “Oltrap”. It is also available in all
Mercury Drug outlets. Or contact the licensee of the technology, Heritage Veterinary
Corporation. They can be reached at Tel. No. 921-8978 and 579-9379.
Another mosquito-born (A. aegypti) disease to watch out for is Chikungunya.
It affects anybody and exhibit the same symptoms but not as deadly as dengue. It is
distinguished from dengue by the presence of anti-CHK antibodies in blood samples
of patients. Cases of chikugunya have been reported in Metro Manila, Laguna,
Pangasinan, and some parts of Mindanao.
The DOH has launched the 4-S Campaign against dengue, namely:
1. Search and destroy breeding places of dengue virus-carrying
mosquitoes. This is done by removing all possible breeding places of
mosquitoes. Examples are: changing water in flower vases once or
twice a week, regular cleaning of roof gutters which can retain water,
draining water from unused old tires, flower pots, tin cans, bottles, and
plastic cups and keeping them in areas where they cannot collect water,
and covering water containers like drums or pails and draining water
from tree holes, base of leaves like those of the bromeliads, coconut
shells and bamboo posts.
2. Self-protection measures that include wearing of long sleeves and
pants, using mosquito nets and applying mosquito repellants.
3. Seek early consultation when symptoms appear, meaning when one
has fever for two days and begin to have rashes, he/she must
immediately consult the doctor at the nearest health center or
hospital.
4. Say no to indiscriminate fogging unless there is an outbreak.
Chordates
Not all members of Phylum Chordata have backbones. Acorn worm is
another chordate without a backbone.

184
Vertebrates
Vertebrates have an internal skeleton that gives them more flexibility in
moving. Fishes, amphibians, reptiles, birds and mammals are members of the
vertebrate group.
Fishes
Students should know that not all sharks attack humans. Except for the great
white, tiger and bull sharks, whale sharks (Butanding) are friendly species. Studies
have discovered that sharks, attack people mistaking them for prey or food
especially those wearing silvery wetsuits. Seals, food to sharks have silvery
covering. Some shark species are attractions in zoos and ecotourism spots. Care,
however, should be taken that these fishes are not abused.
Fish supply has also decreased because of another fishing practice like use
of big boats and fine nets. You can then ask students how this method cause
decrease in fish population. Emphasize the need for people of all ages to be aware
of conserving fish species by following rules set by the government for marine
sanctuaries and laws against dynamite and cyanide fishing. For students living in
fishing villages, they should help the Bantay-dagat in their efforts to implement these
laws. Those living in urban or mountain areas may check the internet, listen to news
or watch TV features and inquire from local government officials on what these
organizations are doing to protect and conserve fish species.
Amphibians
Point out differences of frogs and toads which are the more familiar
amphibians. Mention that there was a time when toads were introduced to the
Philippines to control mosquito population. Mention too that in other places frog legs
are eaten with some restaurants serving them as exotic food. They should however
be aware that these vertebrates also suffer from population decline due to loss of wet
or moist areas where they live.
Reptiles
The large saltwater crocodile Crocodylus porosus are not a threatened
species. They are found in rivers, large lakes, coastal waters, mangroves and
especially in estuarine or brackish water. It can swim long distances. In the
Philippines, they have become extinct in certain areas where they abound before.
“Lolong,” the largest caught saltwater crocodile of Agusan Marsh in Mindanao,
which died recently should be teaching people a lesson on biodiversity. Check out
the internet for an article (http://www.rappler.com/move-ph/23498-lolong-angel-
alcala) written by a Filipino expert on crocodiles. Because of this incident, a non-
government organization encourages government to ban capture of animals from the
wild.

185
The smaller threatened Philippine crocodile can be found only in Philippine
rivers, freshwater lakes and creeks. This crocodile species should be given priority in
study and conservation activities.
Birds
Some members of the bird group have also become a major source of food to
humans like chickens and ducks (including their eggs).
If you are in areas other than those mentioned where Philippine Eagles live,
ask students what they have read or heard about causes of the destruction of the
birds’ habitat.
In 2010, the International Union for the Conservation of Nature (IUCN) has
declared the Philippine Eagle as critically endangered species. Aside from the
causes of its decline in number presented in the student module, add to these illegal
hunting and collection, lessening availability of food, pollution brought by mining and
use of pesticides in nearby farmlands close to where they live. Students should know
that pollution affect the eagles’ breeding. It causes the thinning of their eggshell
resulting to nonhatching of the eggs. Encourage students to read more about
activities of the IUCN.
Mammals
The spiny anteater lives on land. It has spines in between the hairs all over
its body. Platypus on the other hand have thick water proof fur and lives both in
water and land.
Mention that whales are mammals that lack hair. Dugong is also called sea
cow. Ask students to give their observations regarding differences of humans and
other primates.
Ask students if they are aware of television shows that teach about
biodiversity. Convince them that current technologies must be used for learning and
not just as entertainment.
LOW AND HIGH BIODIVERSITY
Tropical rainforests are found mostly in Latin America. Others are in West
Africa, the Pacific Islands and South East Asia including the Philippines. Add that
rainforests serve to trap rainwater that flows into rivers and streams. Plants that
abound in forests minimize soil erosion, landslides and floods. They are also sources
of crops that may resist pests and diseases or produce more harvest and chemicals
that can be made into medicines.
Discuss monocroping. Let them describe and classify it as to having low or
high diversity. This would help them in doing Activity 4.

186
Teaching Tips
1. This is a group work. Make copies of the following photos depending on the
number of groups. If not, just provide names of ecosystems and have
members discuss each for them to be able to answer the questions in the
activity.
A tropical rainforest
Rice Farm
(Source: Philippines. Department of Education. (2009). Science and Technology II. Textbook
What is the importance of
biodiversity to ecosystems?
Activity
4

187
(Rev. ed.). Pasig City: Instructional Materials Development Corporation. p. 337 & 340)
Lake Rotting Log
(Adapted from: Philippines. Department of Education. (2009). Science and Technology II. Textbook
(Rev. ed.). Pasig City: Instructional Materials Development Corporation. p. 335)
Mangrove
(Source: Philippines. Department of Education. (2009). Science and Technology II. Textbook (Rev. ed.).
Pasig City: Instructional Materials Development Corporation. p. 338)
2. Answers to Q69 will depend on the ecosystems you presented.
3. Students should be able to recognize that a banana plantation is an example
of monocroping.
4. In answering Q75, have them recall the discussion about the sea star, crown
of thorns.
5. In answering Q78, encourage students to think of familiar places that have
low biodiversity.
Protecting and Conserving Biodiversity
Pose the questions: What are your responsibilities towards biodiversity for a
sustained supply of food and other resources for all organisms? What actions must
you take to protect and conserve biodiversity? If some of the abundant species
present thirty or fifty years ago in your community are lesser now or have
disappeared, what would the future look like for these organisms?

188
Teaching Tips
1. Have ready copies of the “Priority Pyramid” and the “Making it Happen”
handout. There should be one for each student and for each small group.
2. Part I: My Future World. Brainstorm students’ ideas about the conditions that
they want to see present in the world they will live in the future. Direct
students to answer the questions, “What do you want the future world to be?
“What things or conditions do you want to see 50 years from now?” Give
them time to individually list down about five of such conditions. Then, get
them to share their ideas to the class. Write on the board students’ ideas.
3. Once students have shared their ideas, give them a copy of the “Priority
Pyramid” worksheet. Explain to them that they are going to fill up the blocks
in the pyramid with what they consider as important conditions of the future
that they want. Direct them to the ideas written on the board. Tell students to
rank the conditions from most important to the least. They are supposed to
write on the topmost block the most important condition, the second most
important conditions on the second level, and so on. Students may write
down up to ten conditions. Assist students so that they are able to arrive at a
pyramid with at least three levels (about six conditions).
4. Assign students to groups of four or five. If students have previously been
grouped, you can split their original group into two. Have the students share
their pyramids with their groupmates. They should show their pyramid and
explain how they arrive at the ranking. Then, have students work together to
arrive at a group pyramid. Be ready to help groups who may have difficulty
arriving at a consensus.
5. Then, call the small groups to a whole-class sharing of their pyramids. Ask
each team’s representative to share their top three priorities. The
representative can also briefly talk about how they were able to reconcile
their differences to come up with a group pyramid.
As each group presents their priorities, discuss with them what their priorities
entail. For example, if they prioritized “food for all people”, then they should
see that vast spaces with the appropriate environment and resources are
needed so that a great variety of plants and animals that serve as food can
survive and grow.
I create the future
Activity
4

189
As students discuss each condition, they should realize that everything they
want to see in their future world can be traced, at least in part, to a healthy
environment.
6. Part II: Making it Happen. Lead students to discuss strategies that will help
make their dream future to happen. Distribute copies of the “Making it
Happen” handout. The handout contains various projects, initiatives,
legislations that are on-going and in effect that may in one way or another
already contribute to the realization of the conditions that students wish to
happen in the future.
In preparing the Project/Legislation descriptions, you can include projects that
are initiated by government agencies (local and national), non-government
organizations (national, regional and global), private sector, and even
individuals. You can farther help students to appreciate what other people are
already doing and the value of taking action by describing projects and
legislations that affect their community or locality. When choosing a law or
policy on protected areas for example, you can describe those that pertain to
their locality or community. A great site for information and resources on
biodiversity conservation projects is the Protected Areas and Wildlife Bureau
(PAWB) of the Department of Environment and Natural Resources
(http://www.pawb.gov.ph).
7. Part III: Future Log. Require students to keep a future log for a week. Explain
to them that they should use the log as a diary, where they write all their
activities, behaviors, conversations and thoughts each day of the week. To
make their log easier, instruct them to write these in bullet form, instead of
complete sentences and paragraphs the way they would on a diary.
Encourage students to realize that their actions, words and thoughts can
actually affect their future. At the end of each day, require them to think and
write about how each item in their bulleted list may affect the world around
them, either positively or negatively, and what the consequences could be for
the future.
As students progress from day to day, encourage them to add more ways,
that is, engage in more actions, thoughts and words that will help them
contribute to the conservation of biodiversity in their locality.
“Ocean Treasures”, is a video lesson developed by UPNISMED that can be
used as an alternate activity. It identifies both plant and animal resources found in
our oceans. It also shows how these resources can be used wisely by protecting and
maintaining balance in the different shallow ecosystems in the ocean. The package
consist of a DVD and a Teacher’s Guide with emphasis on concepts, what questions
to ask, a short activity and some formative assessment items which teachers can
give as students view it. You can check out the UPNISMED website for details on
how to procure it.

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Remind students that with understanding of what biodiversity can do for
humans and the whole world, there is no choice but to care for and conserve them.
Encourage them to help in promoting awareness of the importance of biodiversity,
help minimize threats to biodiversity and actively participate in programs and projects
for the protection and conservation of biodiversity.
As a culminating activity, you may have students have a field trip to just a
nearby forest park, zoo or even your school’s medicinal or botanical garden. They
then, can make a report of the biodiversity in such areas.
To summarize the lesson, ask some students what they have learned from it.
Take note if they have alternative conceptions in any of the topics taken up. Check
if they are able to answer the key questions found at the beginning of the module.
Q1. Answers may vary. It is possible that in their community organisms may have a
local name and thus, organism/s may be called with the same name. Or due to
parents’ background, may differ. Examples should be given for those with
same names.
Q2. Answers may vary. Examples should be given for those which are differently
named.
Q3. Students may say that they are confused which is really to be used or they may
wonder why organisms are called in different ways.
Q4. Domesticated cat, dog, wolf and lion.
Q5. Dog and wolf. They belong to the same category up to the genus level.
Q6. No, they cannot produce a fertile offspring because they belong to different
species. Only organisms that belong to the same species can breed and
produce fertile offspring.
Q7. The species row consist of two words/names.
Q8. The first name refers to the genus, the second one to the species.
Q9. Water in both is up to ten (10) times more salty than sea water or both are very
salty environments.
Q10. Possible answers: dirty, small, disease, harmful, present in some food, used
in making medicine, vaccine.
Q11. Cocci are round/spherical/circular. Bacilli are rod-like/narrow and
cylindrical/long. Spirilla are spiral/coiled/twisted.
Q12. Avoid wading, swimming or playing in flood waters which may be
contaminated with animal urine, wear gloves in gardening, cover cuts on the
skin while working in farms, wear footwear in walking in mud, keep homes
and surroundings clean, thoroughly wash hands with soap, wash vegetables
well before cooking.

191
Q13. Farmers, veterinarians, people involved in raising carabaos, people who have
the practice of eating meat from animals which are suspected to die from the
disease (carabaos).
Q14. For clearer observation of the specimen.
Q15. Possible answers: Rodlike/cylindrical and round structures/bacteria.
Q16. The rod-shaped are Lactobacillus, while the round ones are Streptococcus
bacteria.
Q17. Bacillus bacteria are rod-like and cocci bacteria can form chains and called
streptococcus.
Q18. Crops will be supplied with usable form of nitrogen for their growth and
development.
Q19. Through the bladders brown algae would be able to capture light energy by
chlorophyll present in their cells.
Q20. Light is important to algae because they need it to produce food (for
photosynthesis).
Q21. These clams may have fed on the dinoflagellate with poison causing
paralysis of the diaphragm
Q22. Foraminiferans have threadlike extensions, radiolarians have sharp
needlelike extensions while amoeba have blunt extensions.
Q23. They produce food for organisms, green algae serve as food, some brown
algae are source of alginic acid, some red algae are source of food and agar
and carageenan.
Q24. Ascus, ascopores.
Q25. Basidiospores, basidium.
Q26. Many fungi would grow.
Q27. In moist/damp, humid, dark places.
Q28. Liverworts are flat and ribbonlike. Mosses have many small leaflike
structures. Hornworts grow flat leaves on top of each other.
Q29. They have no true roots, stems and leaves that can transport food and
materials to different parts.
Q30. It has big leaves and it is tall almost reaching 1st
floor of the building
Q31. They will provide usable nitrogen to plants or serve as natural/organic
fertilizer.
Q32. Some serve as food, or used in making handicraft items.
Q33. In cool, elevated areas.
Q34. Less oxygen will be available. There will be erosion, less timber, no home for
birds and other animals.
Q35. Alternate cashew, radial garlic, opposite coffee.
Q36. Dicot.
Q37. Monocot.

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Q38. Food (meat and juice), cleaning implements, oil, etc., (accept right answers of
students)
Q39. Home for birds, provide seeds for food, nectar for butterflies, leaves food to
worms, etc. (accept other correct answers)
Q40. Production of oxygen, food for other organisms.
Q41. Weeds, which often grow along with food crops, compete for nutrients
needed by the latter. Such competition results in decreased harvest.
Q42. Animals react quite rapidly to stimuli. (act fast, move fast)
Q43. Sea fan, sea pen (enumerate those in sand ). Jelly fish, etc.,(enumerate
those floating in water).
Q44. They feed on digested food.
Q45. Two.
Q46. They have a single shell. Bivalves have two shells.
Q47. Bivalve, univalve, bivalve.
Q48. Arthropods have exoskeleton, echinoderms have endoskeleton.
Q49. For protection.
Q50. Arachnids.
Q51. Arachnids have four pairs of legs, insects have three pairs.
Q52. The adult A. aegypti has white spots/bands on its body and legs. It has three
body parts: head, thorax and abdomen. It has a pair of wings, three pairs of
legs and pair of antenna.
Q53. It breeds in clean, non-flowing or standing water.
Q54. Possible places in the home where Aedes mosquito can breed include:
containers with water placed under the table’s legs, flower vases, old tires
left outside which can collect rainwater, roof gutters which can retain
rainwater, containers placed under flower pots that collect excess water, tin
cans, bottles, and plastic cups left outside which can collect rainwater,
uncovered water containers like drums and pails, tree holes, bamboo posts
of fences around the house. Breeding places in the school can be flower
vases, containers placed under flower pots, plastic cups or bottles left in the
grounds which collect rainwater, and also tree holes and bamboo posts.
In the surroundings, it can be animal food containers, clean stagnant waters
in canals, potholes, and any container or items that can collect and retain
water.
Q55. It will die.
Q56. Water is important to Aedes mosquito because it is where they reproduce.
If there is no clean, nonflowing water available, no egg will develop into adult
mosquitoes.

193
Q57. Reproduction of Aedes mosquito can be stopped by removing all possible
breeding places of mosquitoes. The following are some ways to do this:
 changing water in flower vases once or twice a week,
 regular cleaning of roof gutters which can retain water,
 draining water from unused old tires, flower pots, tin cans, bottles, and
plastic cups and keeping them in areas where they cannot collect water,
 draining water from containers placed under flower pots or table legs from
time to time,
 covering water containers like drums or pails, and
 draining water from tree holes or bamboo posts
Q58. Insects because it has three body parts: head, thorax and abdomen. It has a
pair of wings, three pairs of legs and a pair of antenna.
Q59. Skeleton of the shark is made of cartilage, that of tilapia is made of bone.
Q60. Toad and tree frog.
Q61. Caecilian.
Q62. Sharp hooked beaks bite, cut or tear prey into pieces,
Q63. Only the legs of birds have scales.
Q64. Possible answers: hunting for food or income, kaingin
Q65. Whales, dolphins, dugong and manatee live in salty waters.
Q66. Some answers are: humans have the ability to walk erect, they have well
developed arms and hands, nails in fingers and toes, lemurs, monkeys and
apes live in trees, humans have communities.
Q67. Mammals differ from other animals in that they have mammary glands that
produce milk to nourish their young and most have hair or fur.
Q68. It has a single or few number of species.
Q69. The answers will depend on the pictures shown.
Q70. Low diversity.
Q71. Many of the banana plants will be affected/damaged or die.
Q72. Banana plants will be toppled down, some may be washed to other areas, or
whole plantation will be wiped out. Small animals living in the plants will also
die.
Q73. Farm helpers will have no income (cannot be paid by owner) and owner will
lose his harvest and consequently his profit.
Q74. There are corals, fishes, sponges, algae, molluscs, seastars, sea anemone
etc. (Students may give other answers as long as they should be organisms
associated with a coral reef)
Q75. Fishes come to the coral reef to breed, molluscs eat the algae present,
sponges will feed on the floating algae near the reef, clownfish feed on
leftover food of sea anemone, etc.

194
Q76. Crown of thorns may eat all the algae in the reef that provide oxygen to the
other animals, leading to death of these organisms.
Q77. With high biodiversity, the risk of damage from pest infestation is minimized
leading to better income or profit, low input of pesticides because different
pests feed on different plants, various soil nutrients will be available to
different plants because of presence of other organisms or nutrients are
recycled, it can support more organisms
Q78. Competition among organisms is less as there are more choices for food,
more shelter and water available to organisms, balance of consumers and
decomposers, less possibility of species extinction, support more organisms.
Biodiversity is importance to ecosystems because of interdependence of
organisms to one another.
Q79. Cornfield, ranch containing grass and cows only, coffee plantation,
Q80. Actual students’ answers. May include: cure for illnesses, food for all people,
etc.
Q81 to Q84. Actual student answers.
Q85. Examples of acceptable answers: Bantay Dagat, Clean Air Act
Q86. DENR, Local government units, PAWB, BFAR
Q87. Actual student answers.
Q88. Actual student answers.

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Making It Happen
(Note: These are some examples. Each project to be included should be described
in detail to enable students to match the project to their priority conditions for the
future.)
1. Programs and projects of the Protected Areas and Wildlife Bureau (PAWB) of the
Department of Environment and Natural Resources
a. Invasive Alien Species Project
b. New Conservation Areas in the Philippines Project
c. The Coral Triangle Initiative
d. Peatland Project
e. Integrated Coastal Resource Management Project
f. Samar Island Biodiversity Project
2. Laws and Policies related to protection and conservation of biodiversity in the
Philippines
a. Republic Acts (e.g., Philippine Clean Air Act of 1999: Republic Act 8749)
b. Executive Orders (e.g., Guidelines for Ecotourism Development:
Executive Order No. 111)
c. Presidential Proclamations (declaring certain places as protected areas
and buffer zones)
d. DENR Administrative Order (declaring certain places for specific
biodiversity conservation activity; e.g., DENR AO 2011-10 declaring
Cabusao Wetland Area in Camarines Sur as critical habitat)
e. DENR Memorandum Circular/Order (e.g., DMO No. 2011-04: Strict
regulation of activities, projects and land uses in all areas proposed for
inclusion in the National Integrated Protected Areas System)
3. The Ramsar Convention and Ramsar Sites in the Philippines
4. Palawan Council for Sustainable Development
5. Organic farming
6. “No fishing” : species, zone and timeframe (e.g., Zamboanga waters: sardines)
7. Herbal medicine
8. Planting of mini-forests in cities and municipalities
9. National Ecotourism Strategy (database of ecotourism sites and protected areas
in each region)
10. Biodiversity Hotspots of the World
11. “No plastic” drive in some cities and municipalities
12. IRRI Rice Seed Bank
13. Species Conservation Programs (e.g., Philippine Eagle Center, crocodile,
tamaraw, tarsier, etc.)
14. SM (Shoemart’s) M.O.B. Day Campaign

197
References
Crisci, J. V., Mclnerney, J. D., & McWethy, P. J. (1993). Order and diversity in the
living world: Teaching taxonomy and systematic in schools. Reston, VA: The
Commission for Biological Education of the International Union of Biological
Sciences in Cooperation with UNESCO.
Hernandez, R.S. (1993, March). Microorganisms in biotechnology [Module]. Quezon
City: UP Institute for Science and Mathematics Education Development.
Khan, M. M. (1988). Azolla agronomy. Laguna: IBS-UPLB and SEARCA.
Strauss, E., & Lisowski, M. (1998). Biology: The web of life (Teacher’s ed.). Reading,
MA: Scott Foresman-Addison Wesley.
Reece, J. B., Taylor, M. R., E. J., & Dickey, J. L. (2012). Campbell biology: Concepts and
connections (7th
ed.). Singapore: Pearson Education
Philippines. Department of Education. (2009). Science and Technology II Textbook.
(Rev. ed.). Pasig City: Instructional Materials Development Corporation
Philippines. Department of Education. (2009). Science and Technology II Teacher’s
Guide. (Rev. ed.). Pasig City: Instructional Materials Development Corporation
University of the Philippines Institute for Science and Mathematics Education
Development. (1996). Plants of the Philippines (2nd
ed.). Manila: Pundasyon
sa Pagpapaunlad ng Kaalaman sa Pagtuturo ng Agham.
Links
Extreme Science. (2013). Deep sea hythermal vents. Retrieved from
http://extremescience.com/deep-sea-vents.htm
Globio. Glossopedia. (n.d.). Species. Retrieved from
http://www.globio.org/glossopedia/article.aspx?art_id=34
Karser, G. E. (2006). The prokaryotic cell: Bacteria. Retrieved from
http://faculty.ccbcmd.edu/courses/bio141/lecquide/unit1/shape/shape.html
http://www.stuartxchange.com/Dilaw.html
www.aquaticcommunity.com/crocodiles/philippine.php
www.mabuwaya.org/index.cfm?p=1EB9CC43-F1ED-2AA3...
en.wikipedia.org/wiki/Tunicate
marinelife.about.com › Education › Marine Life › Sharks

198
What causes malaria? (n.d). Retrieved from
http://www.davidson.edu/academic/psychology/ramirezsite/neuroscience/psy32
4/rebergner/what_causes_malar...2/20/2013
www.iucn.org/about/
http://www.philippineeagle.org/index?pageval=the thephileagle

199
INTERACTIONS
In this module, students will learn about the concept of “Interactions” in which
organisms in the ecosystems acquire energy for their survival. Students should know
that all organisms they observe in the environment interact in order to survive. This
module introduces the idea of flow of energy in an ecosystem through interactions of
organisms in the ecosystems. These interactions can be observed in many ways.
Some interactions are beneficial; others are harmful. There are also interactions in
which populations of organisms are neither benefitted nor harmed.
Teachers should also emphasize the idea that organisms interact with each
other and their environment to meet their basic needs and survive. Interactions
between organisms and their environment are also a familiar scene: carabaos
helping farmers till the soil, earthworms burrowing in the ground may contribute in
the fertility of soil which is beneficial to plants, and birds gathering twigs to build their
nests.
Human intervention has had a range of effects on natural biodiversity.
Agriculture has expanded into environmentally sensitive regions. In its natural state,
an area of land that has shrubs and grasses on it has an inherent tolerance against
flooding, drought and insect infestation. Because of expanding lands for agriculture
and diversification of crops such as growing corn, some ecosystems have become
more vulnerable.
In this module, students will identify the roles of organisms in food chains and
food webs. Students conduct a simulation to investigate how energy is transferred
from one source to another. Students will be able to:
 sequence a food chain to show the transfer of energy from one trophic level
to another trophic level
 identify the organisms comprising a food chain and the function of each
 identify the organisms comprising a food web and the function of each
 describe a food pyramid in terms of the amount of biomass or energy at each
level
 analyze the relationship between energy and matter
 analyse the harmful effects of some farming practices to increase crop yield
 identify alternative agricultural practices which can minimize or possibly
eliminate the problem that go with some farming practices
The module has activities that will help students construct their science ideas
and develop science thinking skills through embedded questions. The understanding
of these concepts and skills will be strengthened through inquiry-based activities
Unit 4
MODULE
2

200
such as making observation, analyzing information and discovering on their own
relationships and connections from the data gathered. The concepts learned in
these modules will prepare students to tackle more abstract science concepts about
transfer of energy in higher grade levels particularly in the topic of photosynthesis
and cellular respiration.
In this module, students gather evidence to understand that organisms in an
ecosystem are tied together by their need for energy. Students execute the activities
that provide them the idea that the Sun's energy is captured by producers and
passed along to other consumers in the food chain. They then demonstrate their
understanding of the flow of energy in an ecosystem by feeding on other organisms.
They will learn these in the succeeding activities. There are embedded questions
both in the discussion portion of the text and within the activities.
Answers to the Questions:
Q1. What raw materials from the environment are needed in the process of
photosynthesis?
Answer: Water and carbon dioxide
In Activity 1, students will read a short article about “Monfort Bat Cave.”
Remind the students to read the procedure. Student should answer the questions
within the activity.
Q2. What are the organisms found in the surrounding area of Monfort Bat Cave?
List them down in the table below.
How do you identify the
components of a food chain in an
ecosystem?
Activity
1
How does energy become transferred from
one organism to another?

201
Table 1. Organisms found in Monfort Bat Cave
Plants Animals
durian trees bats
other trees crows
rats
pythons
monitor lizards
dogs (untamed)
cats (untamed)
humans
Q3. What groups of organisms are considered producers?
Answer: In this situation, the durian trees and other trees are the producers,
providing food to the bats.
Q4. What part of the durian trees and other trees served as food for the bats?
Answer: nectar, fruits
Q5. The population of cave-dwelling bats is declining because they are being eaten
by other organisms. What are these organisms that feed on bats?
Answer: crows, rats, pythons, monitor lizards, cats (untamed), dogs (untamed),
humans
Q6. Among the organisms that feed on bats, are there organisms that possibly feed
on the predators of bats?  Yes _ No
3. Divide the organisms into the following categories as shown in the table below:
Table 2. Categories of organisms living in the Monfort Bat Cave
Producers 1st
Order Consumer 2nd
Order Consumer
durian trees bats crows
other trees rats
pythons
monitor lizards
cats (untamed)
dogs (untamed)
humans
4. Based on Table 2, construct a food chain with at least 3 organisms
representing the producer, 1st
order consumer and 2nd
order consumer.
Producer 1st
order consumer 2nd
order consumer
Energy
from the
Sun
durian trees bats pythons

202
Q7. You have just analyzed by categorizing the organisms according to their trophic
level. In your own words, describe a food chain.
Answer: A food chain is a transfer of energy from the Sun in sequence, for
example, from green plants (convert energy from the Sun into
chemical energy), to animals that eat plants, to animals that eat other
animals. The feeding of one organism upon another in a series of
energy transfers is known as a food chain.
Q8. Without decomposers will producers stay alive? Why?
Answer: No. Decomposers act on dead organisms and change these to simple
nutrients which plants can use again. Without decomposers, nutrients
needed by producers will not be available. Producers cannot stay
alive.
Q9. Without producers, will consumers stay alive? Why?
Answer: Without producers, there will be no food for consumers.
Think of the food your family ate for supper last night. Make a food web
based on your meal. Remember, your food web must have producers,
consumers, and decomposers.
Q10. To which group of organisms do you belong?
Answer: Consumer
Q11. Which trophic level do you occupy?
Answer: Answer will depend on the food web constructed by students.
Definitely, humans occupy the top trophic level in the students’ food
webs.
Q12. Which group of organisms has the greatest biomass? Which has the greatest
energy?
Answer: The producers, example grass, cabbage, and shrub – greatest
biomass and greatest energy
Q13. Which group of organisms has the least biomass? Which has the least
energy?
Answer: The top consumer: hawk
Q14. What happens to the amount of biomass from the bottom to the top of the
pyramid?
Answer: The amount of biomass decreases at each succeeding level from
the bottom to the top of the pyramid.
Making food webs
Activity
2

203
Q15. How much biomass of chicken can 5 000 kg of corn support?
Answer: 500 kg
Q16. How much biomass of humans can the chickens support?
Answer: 50 kg
Q17. How much biomass of humans can 5 000 kg of corn support?
Answer: 500 kg
Q18. Which is more efficient in converting biomass of producers to biomass of
consumers – a meat eater or a plant eater? Give your explanation.
Answer: Plant eater; the same biomass of producers (corn) can support a
greater biomass of consumers (humans) than if one were an animal
eater. (Note: The teacher can explain that in the illustrated
pyramids, if each person has a mass of 50 kg. 5 000 kg of corn can
support 10 plant eaters with a total mass of 500 Kg and only 1 meal
eats with mass of 50 kg.)
Q19. What gas do plants produce that animals use?
Answer: oxygen
Q20. What gas do animals produce that plants use?
Answer: carbon dioxide
Q21. Describe one way by which the following practices may disrupt a food chain
or food web:
 monoculture
 use of insecticides
 use of fertilizers
Note: There are several ways that are suggested in the module. Students can pick
up from the text in the module.
Meat eaters vs. plant eaters
Activity
3

204
Summary
 Energy flow in the ecosystem is a one-way process. Energy flows from the sun,
to the producers, and to the consumers. An ecosystem consists of all the
organisms in an area interacting with one another and the nonliving environment.
 Producers such as plants, algae, and certain bacteria capture the energy of
sunlight to produce food molecules. Consumers such as animals eat or consume
producers and other organisms to obtain energy.
 The flow of energy between organisms can be shown by a food chain or a food
web.
 A food chain is a sequence of organisms used as food and the organisms that
feed on them. It starts with a producer followed by a series of consumers.
 A food web shows the complex feeding interrelationships between organisms in
an area. It consists of interconnected food chains.
 Energy flows through different feeding levels called trophic levels in food chains
and in food webs. Producers occupy the first trophic level. Consumers are at
succeeding trophic levels ending with the top or highest-level consumers.
 A food chain or a food web can be arranged in the form of a pyramid. A pyramid
of biomass shows the decreasing amount of matter or tissue while an energy
pyramid depicts the decreasing amount of energy. The greatest amount of
biomass or energy is at the base of the pyramid. The amount of biomass or
energy decreases towards the top.
 While matter is recycled in ecosystems, energy flows only in one direction 1st
order from producer to consumer to 2nd
order consumer, etc.
 People are the top consumers in many food webs. To increase food production,
they use methods which may disrupt food chains or food webs. They have to
learn how to make decisions to correct these mistakes.
References
Campbell, N. A., Reece, J.B., Taylor, M.R., Simon, E.J., Dickey, J.L. 2012. Campbell
Biology: Concepts and Connections. Seventh Edition. Pearson Education,
Inc. publishing as Pearson Benjamin Cummings, USA.
Lantaw - Philippines Outdoor and Travel Photos 2009: Retrieved March 13 2013
http://www.lantaw.com/2009/10/samal-monfort-bat-cave.html
Department of Education, Culture and Sports. Instructional Materials Corporation.
(1990). Science and technology II: Textbook. Quezon City: Author.

205
THE DIGESTIVE SYSTEM
This module revisits the lessons on organ systems taken up in Grades 6 and
7. In Grade 6, the students learned how the different organ systems work together. In
Grade 7, they were introduced to the levels of organization in an organism of which,
organ systems are but a part.
In this module, the students will learn not just the structures of certain organ
systems that work together but also the processes they undertake to keep the state
of balance in organisms. Emphasis will be given on the digestive system.
Four of the major functions of the digestive system are covered here:
ingestion of food, digestion of food, absorption of nutrients, and elimination of waste
materials. This module covers also the complementary role played by the respiratory
and circulatory systems in the digestion of food.
Start the lesson with a review of the different structures of the digestive
system and their functions. These are lessons the students have learned in Grades
5, 6, and 7. Draw out in your review with the students the concept of interaction
among these structures and the importance of such interaction in the survival of
species. Activity 1A may serve as a motivational activity.
How does the digestive system break down food to
nourish the body?
Unit 4
MODULE
3

206
Activity 1 is a board game that is played with tokens and a die (refer to the
board game on the next page. This game aims to help students identify the organs
that make up the digestive system and describe the function of each organ.
Moreover, the game should also be able to help students describe the interaction
taking place in the digestive system as these organs carry out the digestion of food.
Guide the students through the procedure. The game may be played in pairs
or in groups of 5, at the most. There should be as many tokens as there are
members of the group. The first member to make it all the way through the digestive
system wins the game. As the students play the game, guide them through the
questions that follow. After they have finished the game discuss with the class their
answers to the questions.
Teaching Tips
13. The game is an analogy
of some processes
involved in the digestive
system and not a
simulation. As such, it
has its limitations. The
game aims to help
students to identify the
organs that make up the
digestive system and to
describe the function of
each organ.
14. Discuss with the
students what they
understood about the
concept of digestion and
the processes involved
in the digestive system
after playing the game.
After which, ask them
what other things they
would like to learn
about the digestive
system.
A gutsy game
Activity
1A
Figure 1. The human digestive system.

208
15. During the game, it helps if you post on the board an illustration of the digestive
system or display a model of the human torso -- if available. If not, the students
can refer to Figure 1.
The playing pieces or tokens used in the game represent the food we eat. The
spaces on the game board are a representation of the different parts of the digestive
system through which food passes. Have the students describe the illustrations in
the board game and how these illustrations relate to the digestive system and the
process of digestion. Notice that there are spaces or boxes on the game board that
asks the players to move back several spaces. Ask the students if they can think of
an instance when the food that was just eaten moved back.
Q1. The tokens represent the food that was eaten.
Q2. The spaces on the board game represent the different organs or structures of
the digestive system.
Q3. The directions on some of the spaces describe the different physical and
chemical conditions that affect proper functioning of the digestive system.
Q4. The digestive systems of different representative species of animals are
similar to each other in that they are all made up of a continuous tube
with two openings: the mouth and the anus. But as shown in Figure 2,
certain differences are also noted particularly on the structures that
compartmentalizes the different digestive tracts.
Digestion in Animals
Digestion in animals is carried out physically and chemically. Physical
digestion refers to the physical breaking down of food to smaller pieces; chemical
digestion changes the large molecules in food into their building blocks. In the lower
grades, the students have learned how these processes are carried out in the human
digestive system.
At this point, call the students’ attention to Figure 2. Have them compare the
different structures of the digestive systems of different representative organisms.
How are they alike and how are they different? What structures do some species
have in their digestive system that other species do not have? What purpose do
these structures have in the digestive system of these species?
At the end of the activity, have them visit the library or certain trusted
websites to read more about the parts or structures that are unique to each of these
organisms. Ask the students how these structures and their functions are the same
or different from those of humans.

209
The process of digestion is not unique to humans. Even the simplest animals
-- the invertebrates -- have structures they use to digest food. Refer the students to
Figure 3 and have them describe the process of digestion in Hydra. The students
should be able to note that the Hydra has a ‘digestive system’ that has only one
opening -- the mouth! This is called an Incomplete Digestive System.
Have the students read more about digestion among invertebrates and have
them name other organisms that have incomplete digestive systems. In your
discussion have them compare the digestive system of invertebrates with those of
the vertebrates.
Figure 2. Digestive systems of different representative species of animals.

210
Figure 3. (a) Hollow body of Hydra. The animal takes in food, digests food in its
digestive cavity, and removes wastes through its mouth, (b) is an enlarged part of the
body wall, and (c) the outer part of the wall shows the nematocysts.
Revisit these lessons with the students to help them better understand the
importance of the whole process of digestion. Activity 2 gives emphasis on the
chemical digestion of food. They will discover what enzymes are, which ones are
involved in digestion, and the role these enzymes play in making the nutrients in food
available to organisms.
Chewing breaks down food into smaller pieces. To help students draw out
the idea of smaller pieces of food being more easily chemically digested, have them
think of what happens when they chew a piece of candy rather than waiting for the
whole candy to dissolve.
Breaking down food to smaller pieces increases the surface area of the food
on which enzymes like the amylase found in saliva act. Amylase breaks down large
carbohydrate molecules like starch into simple sugars. This is why you might notice
that a boiled sweet potato tastes a little sweeter after chewing it for a while. Note
however that the sugar in sweet potatoes is starch; it is the simple sugars released
from the breaking down of starch that tastes sweet.
This activity should enable students to describe what happens to food as it
gets digested mechanically and to infer the importance of breaking down food to
speed up its digestion.
A sweet break!
Activity
1B

211
Teaching Tips
1. Explain to students that simple sugars dissolve readily in water. They require
little digestion and are quickly absorbed into the bloodstream. Starches are
also relatively simple and are converted to sugars in the mouth.
2. While sugars and starches quickly can be prepared to go into the
bloodstream, most foods are more complex. Ask students to respond to this
question: if they placed a piece of food (lettuce, meat, bread) into their
mouths without chewing, would it completely dissolve in their mouth so that
the body could absorb the nutrients in it?
3. Explain that the digestive system produce many different chemicals called
enzymes that help digest nutrients. Introduce students to the concept of
enzymes and enzyme actions. The following activities will help them better
understand the role that enzymes play in the digestion of food.
Q5. Breaking the candy to smaller pieces increases the surface area of the food on
which solvents like water and digestive juices act. For which reason, the rate of
the food’s dissolution and chemical digestion also increases.
Q6. Crushing the candy represents the chewing of food -- a form of mechanical or
physical digestion of food.
The stomach is made up of muscles that perform both in the mechanical and
chemical digestion of food. These muscles contract and help the stomach churn its
contents; this turns the food into even smaller particles as it gets mixed with the
gastric juices. The stomach also produces hydrochloric acid -- a strong acid -- and
pepsin -- a digestive enzyme. Together, they start breaking down protein. After
digestion of food in the stomach, it gets moved on to the small intestine as a chyme.
Activities 2 and 3 will try to simulate the chemical environment of the stomach
and the processes it carries out to help in the digestion of food.
The importance of enzymes in the proper functioning of the body cannot be
overstated. The different biological processes such as reproduction, growth, and
development are all influenced by enzymes.
In this activity, the students will be introduced to the nature of enzymes and
their role in the digestive system and the digestion of food. As an introduction, the
discussion on enzyme and its function does not include the chemical reactions in
How do enzymes affect
digestion?
Activity
2

212
which they are involved. Note that the topic on chemical reaction will be taken up in
Grade 9 Chemistry.
After performing this activity, the students should be able to infer the role that
enzymes play in digestion.
Teaching Tips
1. Activity 2 simulates a part of chemical digestion that takes place in the
stomach and the small intestine. In your discussion, the students should also
be able to realize that what they observed is not the whole of chemical
digestion. There are other enzymes involved in the process and each of
these enzymes has a specific reaction that it can catalyze or speed up.
2. This activity is best carried out in groups. A week before you perform this
activity, assign each group to bring the materials that will be used for this
activity.
3. It helps also if you have prepared in advance, setups to show the class.
These setups can serve as their guide.
4. Walk the students through the procedure. There may be steps in the
procedure where close supervision is needed such as in the preparation of
gelatin and bromeliad leaf juice. Remind the students of the precautionary
measures they need to observe in handling heating equipment, hot materials,
and hazardous chemicals such as acids and bases.
Q7. Bromelain prevented the solidification of gelatin.
Q8. Observations made on test tubes 2 and 3 showed this effect.
Q9. Enzymes speed up the digestion of food.
Digestive Enzymes
In Activity 2, the students have explored an important part of the nature of
enzymes; they speed up the chemical reactions that help in the digestion of food.
There are different enzymes involved in the digestive system. In fact, there is a
specific enzyme involved in the chemical breakdown of each of the different food
groups.
Carbohydrases -- which include amylase among others -- facilitate the
digestion of carbohydrates – breaking them down into simple sugars, Proteases such
as Bromelain help in the digestion of proteins into amino acids. Lipases on the other
hand, aids in the digestion of fats and lipids into fatty acids and glycerol.
Bromelain, which is a protease, was used in Activity 2. It breaks down
collagen -- the protein present in gelatin. This change should have been observed in

213
test tubes 2 and 3. Bromelain is an enzyme that is naturally present in the leaves,
stems, and fruits of bromeliad plants such as pineapple, kiwi, and papaya.
Enzyme activity of bromelain and the other enzymes is influenced by different
factors such as pH, temperature, and enzyme concentration. There are certain
conditions to these factors that allow the enzymes to work optimally. In the next
activity, only pH will be considered. Here, the students will investigate the effect of
pH on enzyme activity.
The stomach is naturally acidic. This acidic environment of the stomach helps
kill microorganisms to keep the food safe to the body as it gets moved along the
digestive tract. It also enables enzymes to do their job like in the case of proteases
that work best under acidic conditions. Proteases help in the digestion of proteins.
Activity 3 simulates the acidic chemical environment of the stomach and its
effect on one particular group of enzymes -- the proteases. Some enzymes like a
number of proteases need a certain degree of acidity to optimize their enzyme
activity. That is to say that at a given pH range, some proteases are better able to
help in the digestion of proteins.
Activity 3 should enable students to infer the function of the acidic chemical
environment of the stomach and the intestine in providing an optimal condition for
certain enzymes to speed up the digestion of proteins. They should also be able to
infer the relationship of pH to enzyme activity in general.
Teaching Tips
1. Activity 2 simulates the effect of pH on the chemical digestion of proteins.
This activity is best carried out in groups.
2. Assign each group in advance to bring the materials that will be used in the
activity. Most of the materials they will need in this activity have already been
made available in Activity 2. Replenish only those that have already been
consumed or those that needed replacement.
3. It helps also if you have prepared setups to show the class. This serves as
their guide.
4. Walk the students through the procedure. There may be steps in the
procedure where close supervision is needed such as in the preparation of
gelatin and bromeliad leaf juice. Remind the students of the precautionary
measures they need to observe in handling heating equipment, hot materials,
and hazardous chemicals such as acids and bases.
How does pH affect enzyme
activity?
Activity
3

214
Q10. Digestive enzymes speed up the digestion of food.
Q11. The greatest degree of protein digestion is shown in Test Tube A.
Q12. The least amount of protein digestion is shown in Test Tube B.
Q13. Results show that Bromelain -- a kind of protease -- is better able to speed up
the digestion of proteins under acidic environments.
Q14. Yes, the data support our hypothesis that the greatest degree of protein
digestion will take place under acidic conditions. Or,
No, the data do not support our hypothesis that the greatest degree of protein
digestion will take place under acidic conditions.
(Either way the students answer the question, they should be able to account
for their answers using the data they have gathered.)
Q15. Protein is chemically digested in the stomach and the small intestine.
Start the lesson by revisiting Activities 1A, 1B, 2, and 3 of Module 3. At this
point, they should have learned already that food goes through physical and
chemical digestion. In Activity 4, which is an optional activity for this module, you will
present a video clip to the class. This video clip shows the changes that food
undergoes as it gets digested and what happens to it next once digested. Activity 4
provides an audiovisual summary of Module 3.
Activity 4 is an optional activity. A video clip that tracks the changes that
food undergoes as it gets moved to the different parts of the digestive tract will be
shown to the class. Have the students take down notes as they watch the video clip.
After watching the video clip, guide the students through the questions embedded in
the activity. You can also use these questions to start a discussion on the topic.
In your discussion, the students should be able to describe how the different
organs of digestion – including those of the circulatory, respiratory, and excretory
systems – and the different enzymes and gastric juices released, work together to
break down food, nourish the body, and maintain overall wellness.
More specifically, the students should be able to explain how the nutrients are
broken down into small particles that can be used by the body. They should also be
able to explain how these particles are absorbed into the bloodstream. In the human
body, most of the process of absorption takes place in the intestine. Inside the
digestive tract, the surface area is increased by folds and protrusions (villi and
microvilli) to allow more contact with the materials that pass through it.
A journey into the digestive
system
Activity
4

215
Teaching Tips
1. Activity 4 features a video clip that tracks the fate of food as it is moved all the
way through the digestive tract. You can access the video clip through this
link: http://www.youtube.com/watch?v=e3O1AdlC8bI. Note however, that you
are not limited to using just this video clip. You can use other similar
multimedia resources.
2. It will help if you watch the video clip in advance. This way, you can help the
students to understand the narration better.
3. Have the students take down notes as they watch the video clip.
Alternatively, you can start discussion
4. After watching the video clip, have the students narrate what they understood
about the video clip. You can also use the questions in the Learning Material
to guide the class through the discussion.
Q16. The video clip shows the changes that food goes through as it gets digested
and moved through the different parts of the digestive tract.
Q17. What was shown in the movie is the digestion of a mashed food for infants.
The food disintegrates as it mixes with the liquid content of the stomach.
Other changes were also shown as the food is moved from one part of the
digestive tract to the other.
Summary
The digestive system
carries out the following
processes: ingestion of food,
digestion of food, absorption
of nutrients, and elimination
of wastes (refer to Figure 5).
Have the students
describe each of these
processes. They should also
be able to infer that all these
processes are part of a
continuous biological event
called digestion and
therefore, are related to each
other. These processes work
together to enable
organisms to obtain energy
from the food they eat. Figure 4. Peristalsis in the esophagus.

216
In your discussion, draw out from the students the concept of interaction
among the different organ systems. In this particular case, describe how the
circulatory system helps the digestive system in transporting the soluble particles to
the different parts of the body.
In Grade 9, this topic will be revisited to kick start the topic on respiration –
cellular respiration, in particular – and the respiratory system. Interaction of the
respiratory system with the digestive and circulatory systems will also be covered as
well as the system’s role in the derivation of energy from food.
Figure 5. The process of digestion.
References
Beckett, B. & Gallagher, R. (2001). Modular science: Biology. Oxford: Oxford
University Press
Goldsmith, I. (1969). Human anatomy for children. New York: Dover
Publications
Guyton, A. (1964). Function of the human body. Philadelphia: W. B. Saunders
Ravielli, A. (1963). Wonders of the human body. New York: The Viking Press.
VanCleave, J. (1995). Jan VanCleave’s the human body for every kid: Easy
activities that make learning science fun. New York: John Wiley
Link
Journey of the digestive system
Link: http://www.youtube.com/watch?v=e3O1AdlC8bI

217
NUTRITION AND
WELLNESS
This module explores the connection between nutrition and wellness, the
effects of nutrients in maintaining a healthy body, and how students can apply the
concepts of nutrition to their daily lives.
There are three activities in this module. Activity 1 familiarizes the students
with the food pyramid and the food plate and enables them to track down their food
intake. Activity 2 will lead them into understanding that the human body has nutrient
requirements for proper maintenance, growth, and development, and the severe
consequences of nutritional deficiencies. Finally, in Activity 3, the students plan a 3-
day menu where they can now apply the concepts they have learned in Activities 1
and 2.
What are the nutritional needs of our body?
What happens when the body’s nutritional needs are not
met adequately?
Unit 4
MODULE
4

218
In Part A of this activity, the students will make a record of their daily meals
for 3 days. Give this as an assignment before the start of this module. Show the
Sample Daily Meal Journal (Table 1) to the class. The Daily Meal Journal will
provide the students with a record of what their food intake is. The journal is not
meant to be shared to the class.
Invite a resource person (a school nutritionist, school nurse, or barangay
health worker) to impart information on what nutrients are important for a healthy
diet. Request the resource person to share the recommended dietary allowance of
nutrients for teenagers.
Divide the class into groups of 4-5 students. Ask the students to gather data
on what local produce are available in their province and two nearby provinces.
Use the Food Pyramid (Figure 1) to classify the local produce they have
identified into the food groups indicated in the food pyramid.
Am I eating right?
Activity
1

219
Figure 1. The Food Pyramid for teenagers recommends eating a variety of
foods to ensure that all nutrients are provided in proper amount and balance.
Source: Food and Nutrition Research Institute, Department of Science and Technology
To wrap up Activity 1, have the students compare their food intake with the
recommended variety and number of servings. Inform them that the recommended
number of servings vary across age, activity level, gender, if pregnant or
breastfeeding, or body size.

220
In this activity, the students will be divided into groups of five. Each group
researches on specific nutrients including food sources, functions, and symptoms of
deficiency of the nutrient. If possible, examples of food sources should include local
produce. All of the groups present their findings to the class.
One of the main objectives of Activity 2 is for students to realize that food
directly affects and makes up the structures of the body. A complete diet is
necessary to supply the nutrients that organisms need for growth, development, and
maintenance. Dietary deficiencies in these important nutrients can result in
complications and diseases.
In this activity, students will now apply the concepts that they have learned in
Activities 1 and 2. They will develop a 3-day menu that meets the daily nutritional
requirements as identified in the food pyramid for teenagers. Menus should include
breakfast, lunch, dinner, and two snacks. Emphasize that their menu should include
food products that are locally available. You may ask representative students to
present their outputs.
Using essential concepts in nutrition
in planning a menu
Activity
3
What happens when nutritional needs
are not adequately met?
Activity
2

221
Criteria
4
Outstanding
3
Proficient
2
Satisfactory
1
Needs more
instruction
Required information
in menu
-variety and amount of
food groups
-inclusion of local food
produce
-inclusion of required
meals
All meals are
balanced in
terms of the
variety and
amount of
food groups.
Menu
includes local
food produce.
Menu
includes
breakfast,
lunch,
snacks, and
dinner.
Most of the
meals are
balanced in
terms of the
variety and
amount of
food groups.
Menu
includes
local food
produce.
Menu
includes
breakfast,
lunch,
snacks, and
dinner.
Some (80%
and below)
of the meals
are balanced
in terms of
the variety
and amount
of food
groups.
Menu
includes
local food
produce.
Menu
includes
breakfast,
lunch,
snacks, and
dinner.
Most of the
meals are
not balanced
in terms of
the variety
and amount
of food
groups.
Menu does
not include
local food
produce.
Some meals
(breakfast,
lunch,
snacks, and
dinner) are
missing or
incomplete.
Decide on the appropriate intervention to help the students improve when the
output reflects that the students need more instruction.
You may wrap up the Unit with this statement: Your body needs nutrients for
growth, development, and maintenance. Eating healthy and balanced meals
provides you nutrients that your body needs.
Q1. Rice, rice products, corn, root crops, bread, noodles
Q2. Rice
Q3. Fruits, vegetables
Q4. Fruits – 3 servings; Vegetables – 3 servings
Q5. Include servings of fruits and vegetables in his diet

222
Sample Output for the Take Home Activity
Province Fruits / Vegetables / Root
crops / Seaweeds
Poultry / Livestock /
Fisheries
Albay Malunggay Chicken
Rice Duck
Coconut Beef
Kamansi (ogob) Galunggong
Sigarilyas (puro-pagulong) Kuhol
Jackfruit Shellfish
Sweet potato (kamote)
Seaweeds (lato)
Papaya
Kangkong
Mongo
Sorsogon Rice Crabs
Corn Shrimps
Coconut Native chicken
Banana Beef
Root crops Kuhol
Seaweeds (lato) Dilis
Guyabano Grouper (bataway)
Peanut Shellfish
Ampalaya
Santol
References
Daily Nutritional Guide Pyramid for Filipino Children (13-19 years old). Retrieved
from:http://www.fnri.dost.gov.ph/index.php?option=content&task=view&id=16
76
Philippines. Department of Education. (2009). Science and Technology II textbook.
(Rev. ed.). Pasig City: Instructional Materials Development Corporation.
Philippines. Science Education Center. (1971). Plants of the Philippines (2nd
ed.).
Quezon City, Philippines: Pundasyon sa Pagpapaunlad ng Kaalaman sa
Pagtuturo ng Agham, Ink.

223
CELLULAR
REPRODUCTION AND
GENETICS
This module will focus on the relationships of the chromosome and heredity.
Emphasis is given on the behaviour of the chromosomes during meiosis to
understand the basis of the Mendelian laws of modern genetics.
In this activity, the students should be able to identify in the white fish blastula
and onion root tip slides the mitotic cells based on the descriptions given. The
students should also be able to distinguish these cells from the interphase or non-
dividing cells. Note that during interphase, the chromosomes are not readily seen
because they are thin and uncoiled. For the onion root tip, the interphase cells have
distinct nucleoli, which are readily seen as one or two darkly stained bodies inside
the well-defined nucleus.
Answers to questions:
Q1. Centrioles are found in animal cells.
Q2. Cleavage furrows form in animal cells but not in plant cells. Plant cells have cell
walls, which do not permit the formation of the cleavage furrows.
Observing mitosis
Activity
1
What are the different types of cell division?
How are traits passed on to the next generation?
Unit 4
MODULE
5

224
In this activity, the students should distinguish between mitosis and meiosis.
At the end of the activity, they should also know the role of meiosis in the production
of gametes. Meiosis produces daughter cells that become gametes with only half the
chromosome number in order to prevent the doubling of the chromosome number
every time the gametes fuse during fertilization.
Completed table:
Mitosis Meiosis
Number of daughter cells produced Two Four
Number of chromosomes is halved.
(Yes/No)
No Yes
Pairing of homologous chromosomes take
place. (Yes/No)
No Yes
The daughter cells produced are always
identical in terms of genetic material.
(Yes/No)
No Yes
The teacher should emphasize to the students that during the S phase of the
cell cycle, each chromosome will undergo replication; from one sister chromatid,
each chromosome will now have two identical sister chromatids. During crossing
over in Pachytene stage, however, segments of sister chromatids from homologous
chromosomes are exchanged. This will result in non-identical sister chromatids for
each chromosome, which is seen in Figure 3 (see below). Thus, the daughter cells
produced during meiosis will not be identical in terms of the genetic material they
contain as a consequence of crossing over.
Comparing mitosis and meiosis
Activity
2

225
Figure 3. Crossing over of homologous chromosomes during meiosis I.
This activity would introduce the principle of probability to students using a
simple exercise involving tossing coins. This principle could also be applied to predict
the outcomes of genetic crosses.
In the first part of the activity involving a single coin toss, the students should
discover that because a coin has two sides (Head and Tail), each side would have
an equal probability of coming up. Therefore, a single coin tossed 50 times should
have a ratio of approximately 25 H: 25 T or 1:1. A small deviation might be expected
if the result is not exactly 25:25 due to chance.
If we assume the coin to represent the genotype of a parent, and each face is
an allele, with the head as the dominant allele (H) and the tail as the recessive allele
(h), then this would make the parent a heterozygote.
Tossing coins and probability
Activity
3

226
Q2: As with the coin toss exercise, this parent would be able to produce two types
of gametes, one with H and the other with h, each with equal probability of
occurring.
Q2: Assume that by tossing two coins, you are crossing two heterozygote parents,
and each time the two coins face up, the combination represents the genotype
of the offspring. Therefore, the expected ratio should be ¼ HH, ½ HT and ¼
TT.
Q4: The ratio should remain the same even if the number of tosses increases. In
fact, as the number of tosses increases, the closer the results should be in
approximating the expected ratio.
Q5: The results should approximate the expected ratio of Mendel’s experiments
involving a single hybrid cross.
This activity would allow the students to recognize the different Mendelian
ratios based on the different types of crosses involving parents of various genotypes.
The students are strongly encouraged to remember these phenotypic and genotypic
ratios as it would help them solve for genetic problems involving crosses.
Completed table.
Cross Genotypic Ratio Phenotypic Ratio
1. DD x DD 100% DD 100% dominant
2. DD x Dd (½) DD: (½) Dd (1 or 100%) dominant
3. DD x dd (1 or 100%) Dd (1 or 100%) dominant
4. Dd x Dd (¼) DD: (½) Dd: (¼) dd (¾) dominant: (¼) recessive
5. Dd x dd (½) Dd: (½) dd (½) dominant: (½) recessive
6. dd x dd (1 or 100%) dd (1 or 100%) recessive
Comparing genotypic and phenotypic
ratios for a typical Mendelian trait
Activity
4

227
This activity would teach the students how to solve for genetic problems
involving two loci. In this example, the two loci are both heterozygous (hybrid),
although the technique can also be performed using other genotypes. One thing the
students should bear in mind is that, if the pairs of alleles are found in separate
chromosome pairs, then they should segregate independently of each other.
Therefore, different possible combinations will arise, as shown in Figure 10.
Figure 10. Gametes produced by a dihybrid genotype.
Once the different types of gametes and their expected frequencies are
determined, then the expected frequencies of the different genotypes can be
computed.
RrYy
Round, yellow seeds
RY Ry rY ry
¼ ¼ ¼ ¼
Filling up the Punnett square for a
dihybrid cross
Activity
5

228
Completed table:
NOTE: G = Genotype; P = Phenotype
Q1. Since both parents have the same genotype (RrYy), they would have the
same types and frequencies of gametes: ¼ RY, ¼ Ry, ¼ rY, and ¼ ry.
Q2. For RY: 1/16 RRYY + 2/16 RrYY + 2/16 RRYy + 4/16 RrYy = 9/16
For Ry: 1/16 RRyy + 2/16 Rryy = 3/16
For rY: 1/16 rrYY + 2/16 rrYy = 3/16
For ry: 1/16 rryy = 1/16
Q3. There are 9 genotypes in all (see answer in Q2).
Q4. For RRyy = 1/16
For RrYy = 1/4
For Rryy = 1/8
For RRYY = 1/16
¼ RY ¼ Ry ¼ rY ¼ ry
¼ RY 1/16
G:RRYY
P:RY
1/16
G:RRYy
P:RY
1/16
G:RrYY
P:RY
1/16
G:RrYy
P:RY
¼ Ry 1/16
G:RRYy
P:RY
1/16
G:RRyy
P:Ry
1/16
G:RrYy
P:RY
1/16
G:Rryy
P:Ry
¼ rY 1/16
G:RrYY
P:RY
1/16
G:RrYy
P:RY
1/16
G:rrYY
P:rY
1/16
G:rrYy
P:rY
¼ ry 1/16
G:RrYy
P:RY
1/16
G:Rryy
P:Ry
1/16
G:rrYy
P:rY
1/16
G:rryy
P:ry

229
For this activity, the students should remember that in incompletely dominant
traits, the heterozygote condition is expressed as a distinct phenotype. Therefore,
the genotypic ratio of a particular cross would also become the phenotypic ratio.
Q1. Since the parents produce pink flowers, this makes them heterozygotes (R1R2).
They would produce two types of gametes: R1 and R2, each with ½ probability.
Q2. The genotypes of the offspring are as follows: (¼) red, (½) pink and (¼) white.
Q3. The genotypic and phenotypic ratios are the same: (½) red or R1R1: (½) pink or
R1R2.
This activity should develop in students the ability to infer the most probable
genotype(s), and therefore the phenotype(s), of an unknown individual if the
phenotypes of his/her family members are known.
Completed table:
Mother’s Blood Type Father’s Blood Type Child’s Blood Type
A
A or O A
B
A or AB AB
AB
A or B or AB or O B
O
O O
Inferring genotypes of ABO blood types
based on the parental blood types
Activity
7
Phenotypes and genotypes in
incomplete dominance
Activity
6

230
Brooker, R.J. (2008). Genetics: analysis and principles (3rd
ed). Irwin/McGraw-Hill.
Cold Spring Harbor Laboratory DNA Learning Center. (2 February 2013). How
insulin is made using bacteria. Retrieved from
http://www.dnalc.org/view/15928-How-insulin-is-made-using-bacteria.html.
Klug, W. S., M. R. Cummings, and C. A. Spencer. (2007). Essentials of genetics (6th
ed). New Jersey, USA: Pearson Education, Inc.
Lewis, R. (1999). Human genetics: concepts and applications (3rd
ed).
WCB/McGraw-Hill.
Philippines. Department of Education. (2004). Biology: Science and
technology textbook for 2nd
year. (Revised ed.). Quezon City: Author.
Ramirez, D.A., Mendioro, M.S. and Laude, R.P. (2010). Lecture notes in genetics (9th
ed). San Pablo, Philippines: 7 Lakes Printing Press.

Grade 8 science teacher's guide

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Grade 8 science teacher's guide