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Names: ___________________________________________________
Class Period:____
The Rock Candy Lab
Objective / Purpose:
Students will understand how crystals are
formed in rock by mimicking the process of
crystallization.
Materials:
A large beaker
(500 mL)
100 mL Water
200 mL Sugar
String
Thermometer
Styrofoam Cup per
a group member
Wooden stirrer
per a group
member
Foil
Balance
Scissors
Hot Plate
Background Information:
Ions are the basic building blocks of crystalline material. A solid consists only of
round ion spheres stacked up in an ordered pattern. Ions in the solid are arranged
much like billiard balls in a rack, marbles in a box, cannon balls in a pyramid in the
town square, or round stones in a field stonewall. Since all of these are stacked
spheres there are lots of gaps between the spheres, but like a stonewall the gaps
do not matter, the wall is solid in spite of the voids. Also, like a chipmunk in a
stonewall, things (in our case other ions) can pass through the openings in the solid
without destroying the solid.
Igneous rocks are crystallized from a liquid, molten rock. Because the medium from
which the igneous rock crystallizes is a fluid, the ions that will form the minerals
are able to move freely. The hotter the fluid the greater the movement and
freedom, and the quicker the crystallization takes place. (Did you know that hot
water freezes faster than cold? It does! The ice-resurfacing machine at the iceskating uses hot water!). As the melt cools down the freedom of movement
decreases and the ions must fit together into a solid. The ions are of different
sizes and there are only certain ways that they can fit together depending on their
chemistry. But the ions are still in a fluid so they can still easily get to where they
ought to be and form a strong solid. Have you ever run out of ice cubes and been
Names: ___________________________________________________
Class Period:____
impatient for new cubes to freeze? When you check the ice cube tray, you find
that you have a hollow ice cube with water in the center. Crystallization starts at a
point, the water ions move to where crystallization started and add to the already
formed crystals until the whole cube is solid.
In Metamorphic rocks there never is a melt. The recrystallization takes place in the
solid. The metamorphic process forms new minerals from the ions already in the
rock. Just like igneous rocks, the new crystals start at a point and bring to them
the ions they need to grow. The ions are not freely moving as they were in the fluid
igneous rock. The only way they can reach the new mineral is through the voids
(spaces) in the ions that are already there, just like the chipmunk in the stonewall.
In this way, new minerals form by bring to them the material they need and sending
away the material they do not need, all in the solid, until you have a new rock made
up of new minerals consisting of new arrangements of the same old ions.
Pre Lab Questions:
1. How are metamorphic rocks formed?
2. How are igneous rocks formed?
3. Draw the rock cycle. Make sure to include the following terms:
sedimentary rock, igneous rock, metamorphic rock, compacted
sediments, melting and then cooling of rock, heat and pressure
applied
4. How is crystallization different in igneous rock versus metaphoric
rock?
Names: ___________________________________________________
Class Period:____
Procedure:
Part 1
5. Find the mass of your small 100 mL beaker. (Data Table)
6. Get 200 mL of sugar and measure the mass of the sugar. (You may
have to weight the sugar in increments of 100 mL because the mass
is too large to find in one try.) (Data Table)
7. Once you have weighed the sugar, dump it into your large beaker.
8. Get 100 mL of water in your small beaker and measure its mass.
Record the mass of the 100 mL of water. (Data Table)
9. Dump the water into your large beaker.
10. Record the temperature of the sugar water solution. (Data Table)
11. Put the large beaker with your sugar water solution on the hot
plate. Make sure the outside of the beaker is clean and dry. Turn
the heat on the hot plate up to 8 or 9. Record the temperature of
the solution every minute until the solution dissolves. The solution
will be fully dissolved when it turns clear. Make sure to record the
final temperature of the solution when it is fully dissolved. (Data
Table)
12. Let the solution cool. Have your teacher carefully remove the
beaker from the hot plate to expedite the cooling process.
13. Once the solution has cooled to below 45 C, get a Styrofoam cup
for each group member. Have the teacher pour the solution evenly
into each cup.
14. Get a piece of string for each group member and rinse it under the
faucet. Tie the string to a wooden stirrer. The string should be
long enough to dip into the solution when hanging from a pencil
above the cup but not touch the bottom of the cup.
15. Rub some sugar crystals onto the string so that the string has a
light coating of sugar crystals on it.
16. Place the wooden stirrer over the mouth of the beaker so that the
string is hanging down into the sugar water solution.
17. Cover your beaker with foil. Label your beaker with your names of
your group members and your class period, using a pencil.
18. Store the beaker in a safe place, following your teacher’s
directions.
Names: ___________________________________________________
Class Period:____
Results:
Data Table #1
Quantity
Recorded Value
Mass of small beaker
Volume of water used in Liters
Mass of 100 mL of water in grams (g)
Mass of 100 mL of water in kilograms (Kg)
Mass of 200 mL of sucrose in grams (g)
Initial temperature of solution before
heating (˚C)
Final temperature of boiling solution (˚C)
Molarity of solution
Molality of solution
Data table #2
Time (minutes
1
2
3
Keep going until all solute is dissolved
and solution is boiling
Temperature (˚C)
Names: ___________________________________________________
Class Period:____
Post Lab Questions:
1. Based upon your observations, did you mimic the process of crystals
forming in an igneous or a metamorphic rock? Explain your answer.
2. Crystals are not formed instantly. Your rock candy will take a few
days to form. Look up and write how long it takes for crystals to be
formed in igneous and metamorphic rock.
3. Quartz is a commonly found crystal. What type of rock quartz is
often found in?