CHEMICAL CHANGES AND EQUATIONS __________________________________________________________
PURPOSE
In this experiment, you will work with four classes of chemical reactions – synthesis/combustion,
decomposition, single displacement and double displacement. You will attempt to identify some of the products
and write balance chemical equations.
MATERIALS
2 large test tubes, 2 small test tubes, glass bend with stopper, burner, scoopula, test tube holder, ring stand,
test tube clamp, test tube rack, funnel beaker, wire gauze, Limewater, copper II sulfate, 3M hydrochloric acid,
mossy zinc, filter paper, sodium carbonate
PROCEDURE
DECOMPOSITION
1. Obtain one small scoopula full of copper II carbonate and place it in a large dry test tube.
2. Fill a small test tube about half full of limewater, Ca(OH)2 (aq), into a small test tube. Place the end of
the right angle glass tube in the limewater as shown in Figure 1.
3. Heat the tube containing the copper II carbonate while holding the end of the glass tube in the
limewater solution. Continue heating until you observe a change in both test tubes. A cloudy
appearance in the limewater indicates the presence of CO 2. Take the test tube with the limewater away
from the glass tube and then shut off the heat.
4. Let the test tube cool and empty the solid into the proper container and rinse the limewater down the
drain.
SINGLE DISPLACEMENT AND SYNTHESIS/COMBUSTION
1. Use the apparatus from the Decomposition part and arrange it as in Figure 2. Place a small piece of
mossy zinc in a large test tube and add 5 mL of 3M hydrochloric acid. Insert the rubber stopper
containing the glass tube. CAUTION: Keep away from open flame!
2. A reaction should occur and a gas should escape from the tubing. With the glass tubing turned up and
the small test tube turned up side down, collect some of the gas being liberated.
3. Remove the test tube containing the gas from the glass tubing, keeping it inverted, and bring a burnin
splint near its mouth. (This can be obtained from the teacher’s desk.) A “pop” or “bark” indicates the
presence of hydrogen gas.
4. Dispose of solid waste in the appropriate container and rinse the liquid down the drain.
DOUBLE DISPLACEMENT
1. Place of small scoopula full of copper II sulfate in one large tst tube and a small scoopula full of sodium
carbonate in another large test tube.
2. Add approximately 5 mL of distilled water to each test tube. Swirl or shake until the solid is dissolved.
3. Pour the copper II sulfate solution into the sodium carbonate solution. Mix thoroughly.
4. Filter the products of the reaction. Collect and save the filtrate and the solid. Rinse the solid in the
filter paper three times with distilled water
5. Using a nichrome wire perform a flame test and the solid and then on the filtrate.
6. Dispose of solid wate in the appropriate container and rinse the liquid down the drain.
CONCLUSION
1. How can you tell if a chemical reaction has occurred? What are some distinctive changes that can be
observed?
DECOMPOSITION
2. Write the word equation for the two reactions in this section.
3. Write the balanced equations for the reaction in this equation. Be careful to include the correct
formulas, states of matter and energy.
4. Label the balanced equations as exothermic or endothermic.
SINGLE DISPLACEMENT AND SYNTHESIS/COMBUSTION
5. Write the word equation for the two reactions in this section.
6. Write the balanced equations for the reaction in this equation. Be careful to include the correct
formulas, states of matter and energy.
7. Label the balanced equations as exothermic or endothermic.
8. In this section the test for hydrogen was the sound resulting when some of the gas explodes. Do
any other gases have this characteristic? If so, name one.
DOUBLE DISPLACEMENT
9. Write the word equation for the reaction in this section.
10. Write the balanced equation for the reaction in this equation. Be careful to include the correct
formulas, states of matter and energy.
11. Label the balanced equation as exothermic or endothermic.
FIGURE 1
FIGURE 2
small
test
tube
small
test
tube