OBJECTIVES:
1. You will observe a decomposition reaction.
2. You will use a model to write a balanced equation of the reaction.
MATERIALS:
1 gram of glucose
an old test tube
wire test tube holder
test tube rack
burner
atomic models: red (6), black (6) and yellow (12)
22 sticks, 2 springs
cobalt chloride paper
PROCEDURE:
1. Place one gram of glucose in the test tube.
2. Use a wire test tube holder to hold the test tube in the burner flame.
Heat the side near the bottom. Be sure the test tube is facing
away from all classmates.
3. Observe the contents of the test tube as you heat it.
4. Touch the cobalt chloride paper to the liquid at the mouth of the test
tube. If the liquid is water, the paper will change from blue to pink.
over
5. Referring to the diagram, construct a model glucose molecule using the
following colors: black = carbon, red = oxygen, and yellow = hydrogen.
6. Simulate the decomposition you observed in the test tube by breaking your
glucose model into water molecules (H2O) and carbon atoms (C). Make as many
water molecules as possible using only the atoms contained in the glucose
molecule. Make a pile of the loose carbon atoms.
ANALYSIS:
1. How many water molecules did you make from your glucose model?
How many carbon atoms did you count?
Realize that all these water molecules and carbon atoms came from a single
model glucose molecule, which we can represent as C6H12O6.
2. In sentence form, explain what happens to glucose when it is heated. Describe
and name the products.
3. Using chemical symbols for glucose, carbon, and water, translate your
sentence into a chemical equation.
We refer to this equation as a balanced chemical equation, meaning
that the equation has the same number of each kind of atom on each side of
the arrow.
Questions? Comments??
Kathleen R. Kreidler