Chapter 7_Particulate Model of Matter

Model of Matter — The Particulate Nature of Matter7
T H E M E B : MODELS
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Learning Outcomes
• show an awareness that according to the Particulate
Nature of Matter, matter is made up of small discrete
particles which are in constant and random motion
• show an understanding of the simple model of solids,
liquids and gases, in terms of arrangement and
movement of particles
• use models to explain melting and boiling in terms of
conversion of the three states of matter

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Learning Outcomes
• use models to explain expansion and contraction,
and the conservation of mass during these
processes
• compare the properties of solids, liquids and gases
in terms of arrangement and movement of particles
• show an appreciation of how in practice, models are
constructed to explain phenomena
• show an appreciation of scientific attitudes such as
creativity and open-mindedness in creating models
to explain the fundamental nature of things and the
willingness to re-examine existing models

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Part I

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What differences are there among solids,
liquids and gases?
Why is the particulate model of matter
important?

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What is matter made of?

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What is the
science behind
making
popsicles?

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7.1 What Is Matter Made Of?
• The particulate theory of matter describes
what matter is made of.
• Scientists believe that matter is made up of very
small particles. A particle is a word we use for a
small piece of matter.
• We can see small pieces of sugar.
However, scientists believe that
sugar is made up of even smaller
particles that we cannot see.

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Evidence for spaces between particles
• If 30 cm3
of water is mixed with 30 cm3
of alcohol,
the total volume is less than 60 cm3
. Why is this so?

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Evidence for spaces between particles
• If we mix 30 cm3
of rice and 30 cm3
of
beans, the total volume is also less than
60 cm3
.
• This is because there are spaces between
the rice grains and the beans. On mixing,
the rice grains move into the spaces
between the beans.
• This suggests that water and alcohol are
also made of particles and that there are
spaces between the particles.

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In step 2 of making popsicles, we add
sugar to water and obtain a sugar
solution as a result. Where do the sugar
particles ‘disappear’ to?

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Evidence for different spacing of particles in
solids, liquids and gases
• Gases are easier to compress than liquids or solids.
• Click on the arrows to compress the balloon and the
rock.

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Evidence for different spacing of particles in
solids, liquids and gases
• The particles in a gas are far apart. When we
squeeze a balloon, we are actually pushing the
particles closer together.
• The spaces between the particles of a solid are too
small. We cannot push the particles closer to one
another and hence we
cannot compress solids.

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Evidence for movement of particles
• If a bottle of perfume is opened in a corner of a room,
the smell of perfume spreads to all parts of the room.
This suggests that small invisible perfume particles
are moving.
• The movement of the particles of matter is described
as random, that is, they move in all
directions and not in a specific one.

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1. What do scientists believe matter is made up of?
2. There are spaces between particles of matter.
How do the spaces differ in solids, liquids and gases?
3. Give some everyday examples to show that particles
are in motion.

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• In science, we make models to understand things we
cannot observe directly.
• As particles of matter are too small to be seen,
scientists have constructed a physical model to show
how particles in the solid, liquid and gaseous states
of a substance are arranged. It is called the
particulate model of matter and helps us to explain
the particulate nature of matter.
• This model also helps us to visualise what solids,
liquids and gases are like on the inside.
7.2 How Can We Understand the
Particulate Nature of Matter?

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Using the particulate model of matter to
explain properties of matter

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Solids

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Liquids

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Gases

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explain expansion and contraction
• Substances expand when heated and contract when
cooled.
• When cooled, particles lose energy, move slower and
closer to one another. Thus, the volume decreases.
• When heated, particles gain energy, move faster and
further away from one another. Thus, the volume
increases.

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explain expansion and contraction
• During expansion and contraction, only the
distances between the particles change.
• The size and mass of the particles do not change.
• We can use the particulate model of matter to
predict that the mass of the substance remains the
same, although the volume of the substance
changes when it expands or contracts.

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Some water is heated in a saucepan.
What happens to the motion and spaces
between water particles when heat is
applied? How does this affect step 2 of
making the popsicle?

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1. Use the particulate model of matter to explain the
following.
(a) A liquid is diffcult to compress.
(b) If we squeeze a solid, its shape and size do not
change.
(c) If we squeeze a balloon, its shape can change.
(d) A hot gas is less dense than the same gas when it
is cold.
(e) A liquid can flow and take the shape of its
container.
Journal Entry

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3. In which state of matter are the particles
(a) closest together?
(b) moving the fastest?
(c) able to move short distances only?
Journal Entry

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Part II

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• The particulate model of matter can be used to explain
changes of state.
• During a change in state, the temperature does not
change. The energy added during the change of state is
used to move particles further apart.
• When water boils, the temperature remains at 100 °C
until all the water has changed into steam.
• The energy added during this change is used by the
particles to increase the distance between them.
7.3 Using the Particulate Model to
Explain Changes of State [Optional for N(A)]

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Changes of state in matter
Click the arrows to view the process.
http://www.dlt.ncssm.edu/TIGER/F
lash/phase/HeatingCurve.html

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Heating Curve
Why does the
temperature
remain the
same?Solid melting
Liquid boiling
What do and represent?

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Heating Process

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What happen when heat is applied to
liquid
• Particle will gain kinetic energy
• Moves faster as temperature rises
Boiling
Particles have energy to overcome the forces(of
attraction) that hold them together
Liquid become gas
Temperature where it occurs is boiling point

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In step 4, the lemon mixture is poured
into a mould which is then placed in the
freezer. What will happen to the
distance between the particles of the
mixture as it cools?

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1. In making a solid metal object, a liquid metal is poured into a container called a
mould. The mould gives shape to the metal when it cools and hardens. How does
metal casting make use of the different characteristics of liquids and solids?
2. Solid X turns into a liquid at 80 °C and into a gas at 140 °C. Describe the changes in
the particles of X when it is heated from
(a) 70 °C to 85 °C, (b) 85 °C to 145 °C.

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Chapter Review

Chapter 7_Particulate Model of Matter

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