Expo 12 Discussion QuestionsThink about the cooperative learni.docx

Expo 12 Discussion Questions
Think about the cooperative learning lesson plan you have
developed for studying Crystal Growing and the Rock Cycle.
What problems do you envision occurring? Select the most
problematic issue and elaborate on it on the discussion board.
Module 5 Activity
Consider the lab you have just completed, Experiment 12, and
the processes you went through. Now, assume this experiment
were to be conducted in your classroom in groups of four.
Create an age appropriate lesson plan in which you conduct this
experiment using cooperative learning, while still maintaining
the integrity of the 5E Model. Submit your lesson plan as a
word document.
Hands-On Labs SM-1 Lab Manual
91
EXPERIMENT 12:
Crystal Growing and the Rock Cycle
Note: Part One of this lab should be performed at least 10 days
before your report due date.
Read the entire experiment and organize time, materials, and
work space before beginning.
Remember to review the safety sections and wear goggles when

appropriate.
Objectives: To grow synthetic crystals from a supersaturated
solution by evaporation,
To measure the interfacial angles of minerals,
To make sugar “glass,”
To understand the role of evaporation in mineral growth, and
To determine the dissolution point of certain crystals.
Materials: Student Provides: Pan, small
Spoon or blunt knife
Cup saucer
Stovetop burner
Refrigerator
50 g sugar
From LabPaq: Tweezers
Protractor
Ruler
Magnifying hand lens
Digital scale
100-mL Beaker
3 Petri dishes, large
Thermometer
Set of 18 numbered minerals
Igneous rock sample #19
Sedimentary rock sample #36
Metamorphic rock sample #47
Epsom salt: Magnesium Sulfate Heptahydrate,

MgSO4 · 7H2O
Alum: Aluminum Potassium Sulfate Dodecahydrate,
KAI(SO4) 2 · 12 H2O
Discussion and Review: The textbook definition of a mineral is
“a homogeneous,
naturally occurring, solid substance with a definable chemical
composition and an
internal structure characterized by an orderly arrangement of
atoms in a crystalline
structure” (from Earth; Portrait of a Planet; Stephen Marshak
(Norton, 2005).
A crystal grown in a lab is not a true mineral since it did not
form by geologic processes.
However, crystals grown in a lab are virtually identical to true
minerals in many other
92
aspects: they are solid, inorganic, homogeneous, and have a
definite chemical
composition and an ordered structure.
By growing crystals in a laboratory setting you will be able to
investigate the different
properties that define a mineral. In addition, growing synthetic
minerals can offer insight

into the factors that affect the crystal growing process in a true
geologic setting. By
“watching” your crystals grow, you’ll be able to better
understand how crystal faces
develop in rocks and what influences them, plus you won’t have
to wait through
geologic time to view the results!
Since you will know the composition of the material that went
into your crystals and
guided the crystal growth from beginning to end, you’ll be able
to identify your crystals
easily. However, you may have picked up a “pretty rock” at one
point or another in your
life and wondered how to go about identifying it. Since all
rocks are composed of a
mixture of one or more minerals, the first step in identifying
that pretty rock is identifying
the minerals of which it is composed. Minerals are identified on
the basis of several
different physical characteristics which can be determined
through tests, and you will
perform some of these tests with the crystals you grow. This
will help to increase your
confidence about identifying minerals. Eventually you’ll be able
to identify each mineral
in your LabPaq by using those same tests, and this knowledge
will then help you
identify rocks.
The Law of Interfacial Angles, first described by Nicolaus
Steno in 1669, is one
characteristic or test used to distinguish between minerals. This
law states that the
angles between the faces of a crystal are constant for that
particular mineral, no matter

how large or small the faces are. Thus, if you know the
interfacial angles for a particular
mineral, you can identify it by this rule.
Crystal form is another physical characteristic used to identify
minerals. Some of your
larger crystals should show a distinctive geometric shape. Look
at crystals displayed by
several different minerals in your LabPaq and you’ll notice their
different shapes. A
crystal’s shape is indicative of how the individual molecules are
arranged in the crystal
and is an excellent means of identification in minerals that
exhibit good crystal form.
Unfortunately, as you will see in growing your own crystals,
good crystal form is rare
due to competition for space during the growth process. Your
crystals’ edges and
corners may be inter-grown with other crystals, and the bottoms
will be flat due to the
crystals growing upward from the flat surface of a petri dish.
However, most of your
crystals will tend to have the same general shape: perhaps a
cube, an octahedron, or a
rectangular form. This is the mineral’s crystal form. Crystal
form can be distorted into
needles, flattened, or elongated into prisms. Competition for
space can cause a
mineral’s crystals to not have any discernable geometric shape
at all; this is shown well
in igneous rocks which are composed of several different
minerals. To verify how
competition for space distorts their shape, examine your
LabPaq’s igneous rock sample
#19 with your hand lens and try to discern the geometric shapes
of the crystals it

contains.
93
The Rate of Crystal Growth forms a basis for identifying
igneous rocks since all igneous
rocks are formed from the cooling of magma. Igneous rocks are
said to be phaneritic if
the individual minerals are large enough to see and aphanitic if
the individual minerals
are too small to see with the naked eye. This size of the mineral
crystals directly relates
to how rapidly the rock cooled. In some cases, the lava cools so
rapidly that its
molecules do not have sufficient time to organize into crystals
and instead form into a
volcanic or natural glass like obsidian. Volcanic glass is
essentially a super-cooled liquid
blob with no crystals. This lab simulates creating natural glass
with molten sugar.
Chemical Sedimentary Rocks can form from the evaporation of
seawater which
concentrates the chemicals in solution to the point where the
chemicals will eventually
precipitate out of the water and form minerals. The two most
common minerals to form
in this way are gypsum and halite. Gypsum and halite are names
for both minerals and
rocks; if the mineral deposit is large in scale, it is designated a

rock unit as opposed to a
smaller mineral occurrence. Mineral sample #9 and sedimentary
rock sample #36 are
examples of a material in both its mineral and rock forms. An
example of a halite
sedimentary rock unit is the salt flats around the Great Salt
Lake in Utah. An example of
a halite mineral occurrence would be if several halite crystals
were found in the crevice
of an igneous rock along the ocean shoreline. In lab we will
grow Epsom salt and alum
crystals by the evaporation method. The crystals you grow will
be sufficiently small in
scale and so would be considered mineral occurrences if they
were formed by natural
processes.
Metamorphic Rocks are formed by heat, pressure, and/or the
introduction of fluids like
water and magma that alters the preexisting rock. Metamorphic
rocks sometimes
crystallize new minerals as part of the metamorphism process;
garnet crystals are a
good example of this. A metamorphic rock must stay at least
partially solid at all times
and never transform into a liquid during metamorphism;
otherwise it becomes an
igneous rock. However, chemicals in solution can be dissolved
out of the host rock,
transported to another place, and crystallize into new minerals
during metamorphism.
This lab will show how metamorphic rocks crystals can dissolve
and reform naturally.
In all crystal formation cases, the crucial component is a liquid
solution. This lab will

determine the temperatures at which our newly formed crystals
will dissolve into
solution. Dissolved minerals will precipitate out of a saturated
solution at temperatures
below their melting point. As you can see, many aspects of
crystal growing can have
applications to the different types of rock. Hopefully by
completing this lab you will gain
a better appreciation of the rock cycle.
PROCEDURES:
Part One: First, you will investigate the process of mineral
crystallization by allowing
Epsom salt and alum crystals to form by precipitation from
evaporating water.
1. Create Epsom salt crystals as follows:
94
A. Turn on and open the digital scale’s lid. With an empty
beaker on its weighing
surface, press the scale’s tare or zero button so it reads “0”
grams. Add Epson
salt to the beaker until the scale reads exactly 30 grams. Pour
the Epson salt into

a small pan.
B. Measure 50 mL of warm tap water into a beaker and add the
water to the pan of
Epsom salt. Stir well. If the Epsom salt does not fully dissolve,
place the pan on a
stovetop burner and turn the heat on low. Constantly stir the
contents as the pan
slowly heats until you reach the point, but not beyond, where
the Epsom salt is
completely dissolved. Do NOT boil.
C. Remove the pan from the heat and pour its saturated solution
into a petri dish. A
saturated solution is one that contains as much dissolved solute
as it can under
existing conditions and no additional quantity of that solute can
be dissolved in it.
D. Wash the pan and beaker with dish soap, rinse, and dry well
for their next use.
E. Prepare a label by writing on the top half of a 4x4” sheet of
paper: Science
Experiment – Not Dangerous – Please Do Not Disturb. Fold the
paper in half so
that a petri dish can sit on one half and the writing will face out
and be
immediately noticeable.

F. Set the petri dish, uncovered, with its label in a safe place
where it will not be
disturbed, jiggled, bumped, or otherwise moved and where
natural evaporation
can take its course, preferably in a sunny, dry area. Within a
few days you should
see crystals beginning to form in the petri dish. Depending upon
the humidity in
your area, your dish should be fully evaporated and your
crystals fully formed
within 6 to 9 days. Don’t worry if for several days there is
nothing in the Petri
dish. Once crystallization begins, it will proceed quite rapidly.
G. Once the water has completely
evaporated, allow the crystals to dry out
for 24 hours and then examine them
closely with your hand lens. There may
still be some residual water underneath
the crystals. Record your observations
and draw a sketch of the specimen’s
crystal form. The photo at right is of
Epsom salt crystals grown by the
author. As you can see from the
picture, they are not museum-worthy
specimens. Due to competition for space in the Petri dish and
the
supersaturated conditions, the crystals are very crowded
together.
H. Do NOT discard this petri dish or its contents; they are used
again in this lab.

95
2. Create alum crystals by following the above
instructions, A through H, except this time you will
measure and dissolve only 10 grams of alum in
50 mL of water. The photo at right is of alum
crystals. Again, competition for space and rapid
growth in a supersaturated solution leads to
crowding of crystals.
Part Two: Measure the interfacial angles of different mineral
crystals.
1. Select the best four minerals from the LabPaq’s 18 numbered
minerals that show
good crystal form plus one of the best Epsom salt and alum
crystals grown in Part
One.
2. Prepare a data table similar to Table 1 below, and record the
numbers of the
LabPaq minerals selected for measuring.
Data Table1:1

Interfacial angle measurements
Mineral No. Angle 1 Angle 2 Angle 3 Angle 4 Average
#
#
#
#
Epsom Salt
Alum
3. Measure interfacial angles of the four selected mineral
crystals. It will not be easy to
find good crystal interfacial angles as you must try to
differentiate between the
external form the mineral takes when it grows and the form it
may show when it
breaks. Your samples will probably contain many parts of
broken crystals, but they
should also show a few crystals that are reasonably well-
formed. A further
complication is that the crystals of most minerals have more
than one set of
interfacial angles. Try to recognize and measure the
interfacial angles of similar faces for similar crystals at the
same adjacent crystal faces. To do this:
A. Hold the straight edge of a ruler against the line of one
crystal face and the protractor against the adjacent
crystal face as shown in the following illustration. The
straight-edge ruler should intersect the protractor at an
angle as shown. Tweezers and a hand lens will be

helpful in this process. Record the angle in your table.
96
B. Try to find at least two, but preferably four, interfacial
angles in each mineral to
measure. Record each measurement in your data table.
C. For your home-grown crystals, disregard the angles between
the bottoms of the
crystals where they adhered to the petri dish. Since your
crystals were prohibited
from growing into the petri dish, they will not show interfacial
angles or crystal
form in all directions. Measure the angles as best you can, using
your hand lens
and tweezers to assist you if needed. You may have trouble due
to the small size
of the crystals. Record any measuring problems you encounter
in your lab notes.
D. Compute and record the average interfacial angles of the
crystals for each
mineral and your home grown crystals. You need to compute the
average for the
measurements taken because the method of measuring is too
imprecise to
discover the actual constant angles. To compute an average, add
together the

measured angles of each mineral and divide this total by the
total number of
measurements taken. For example, assume the angle
measurements for mineral
#8 were 102, 104, 100, 101, 103, and 102 which totals 612.
Divide 612 by 6 and
you arrive at an average angle of 102.
Part Three: Now you will observe how a crystal growth is
affected by its cooling rate.
1. Forming crystals through rapid cooling:
A. Look closely at the sugar crystals in your packet. Use your
hand lens to observe
them carefully and make a sketch of the sugar crystals’ shape.
B. Place a clean, dry petri dish on a saucer.
C. Measure 50 grams of table or raw sugar and place it in a
small dry saucepan.
Heat and stir over very low heat until, but not beyond, the point
where all of the
sugar is completely melted into a liquid solution. Do not add
any water. Also, do
not overheat the sugar or you’ll soon have caramel candy!
Continuously stir the
sugar over very low heat just until it is completely melted into a
liquid. BE
CAREFUL! MOLTEN SUGAR CAN CAUSE NASTY BURNS!

D. Once the sugar has completely melted, immediately pour it
into a petri dish
resting on the saucer which will guard against spills and
potential burns while
transporting the melted sugar. Also, take care because the Petri
dish may melt!
Place the saucer with petri dish of sugar solution into your
refrigerator and leave
it undisturbed until it cools completely. This should take only a
few minutes. What
you are doing is trying to replicate lava solidifying while it
cools in the air after
being shot out of a hot volcano.
2. Once the sugar has cooled, take the petri dish out of the
refrigerator and inspect it.
Hopefully you have just made sugar glass, where the cooling
rate was so fast that
no sugar crystals were able to form.
97
3. Use your magnifying hand lens to examine the sugar glass
and observe if there are

any crystals in the sugar glass.
4. Save the petri dish of sugar glass in your LabPaq to observe
in a future experiment.
Part Four: In this step, you will re-dissolve the alum and
Epsom salt crystals you grew
in Part One and find their melting temperatures which by
inference should be the same
as their maximum crystallization temperatures.
1. Re-dissolve the Epsom salt crystals by doing the following:
A. First, remove from the dish of Epsom salt any large crystals
you might like to
save or try to grow into larger crystals (optional instructions
follow).
B. Place 50 to 100 mL of tap water into a pan. Measure the
water’s temperature
with a thermometer and record it in your notes. [Note: The
quantity of water used
is not important here, but use the smaller amount if you want to
have a well
saturated solution for further crystal growing. See Optional Fun
below.]
C. With a spoon or blunt knife, scrape all of the crystals from
the petri dish into the

water. Stir and observe. Do the crystals dissolve?
D. If the crystals do not dissolve in Step 1C, heat the pan’s
contents slowly while
stirring. When the crystals are completely dissolved, promptly
remove the pan
from the heat source and measure the liquid’s temperature with
a thermometer.
E. After you have finished this and any chosen optional
experiments (see below),
discard your crystal solution by washing it down the sink with
water.
2. Re-dissolve the alum by following Steps 1A through 1E
above using alum crystals.
Optional Fun Experiments with Crystals:
1. You can pour the saturated solution liquids from Part Four
back into their petri
dishes or other containers and let them evaporate again! If you
wish, you can
crystallize and dissolve your crystals over and over again this
way.
2. Sprinkle a few grains of table salt in your hand, examine
them with your hand lens,
and note their perfectly cubical shape. You can grow larger salt
crystals in a petri

dish or other container similar to the way you grew crystals in
Part One. To make a
saturated solution of salt water, continue to add and stir in small
amounts of salt into
any quantity of warmed water until an additional amount will no
longer completely
dissolve. That’s when you know your solution is fully saturated.
98
3. To grow a larger crystal, first allow the saturated solution to
cool to room
temperature and then pour it into a narrow glass or container.
Tie a piece of thread
around a single crystal you’ve already grown. Suspend the
crystal in the middle of
the solution. Tie the opposite end of the string to a spoon or
knife placed across the
top of the glass. This seed crystal should be suspended in the
middle of the solution
and not be touching the glass. Observe the crystal daily for the
next week and you
should see it grow much larger! You may need to periodically
adjust the string’s
length to ensure the crystal is always submerged in the saturated
solution.
Note: Your LabPaq contains sufficient alum and Epsom salt to

perform Part One’s
instructions twice in case you have a problem on your first try.
Thus, you should
have ample materials left over to make extra solutions and grow
very nice large
crystals. It’s fun to see how large a crystal you can grow!
4. You can also use your new knowledge about crystal growing
to make rock candy.
Prepare a saturated solution of sugar water and suspend a line of
string or a thin
wooden skewer into the water as you would to grow a seed
crystal. Within a few
days crystals will begin growing along the string or skewer and
you’ll eventually
produce a nice sweet snack of rock sugar crystal candy. To
prepare a saturated
sugar solution, continue to add and stir in small amounts of
sugar into any quantity
of hot water until an additional amount will no longer
completely dissolve. That’s
when you know your solution is fully saturated.
Results and Conclusions: Include in your formal report all
tables, graphs, calculations,
lists, sketches, charts, etc. that you produced in this lab.
Questions: (Please give thoughtful and complete responses to
the questions following
this lab and all future labs as required.)
A. Describe in detail the crystal form of Epsom salt, alum, and
sugar.

B. Regarding your sugar glass, how can you relate what you did
to the way in which
obsidian forms? Is your sugar glass phaneritic, aphanitic,
porphyritic, or glassy?
Explain your answer.
C. Do evaporate minerals tend to show good crystal form? Why
or why not? Did the
Epsom salt or alum show better crystal form?
D. Review your table of interfacial angle measurements. Does
the Law of Interfacial
Angles hold true for your mineral samples and the crystals you
grew?
E. At what temperatures did the Epsom salt and alum dissolve?
In a metamorphic
process where there was an introduction of water into a surface-
temperature rock,
would these two minerals probably be among the first or last to
dissolve? What if the
rock was buried deep in the earth and heat was also part of the
metamorphic
process?
SM-1 Manual COLOR 105 08-17-07.pdf

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