Lab 4 What is the Law of Conservation of Mass?
Purpose: To observe the law of conservation of mass in chemical reactions
Method: Students will perform several chemical reactions and analyze the results in terms of the
law of conservation of mass.
Vocabulary: Law of conservation of mass, reactants, products
Hypothesis: Compare the mass of the reactants to the mass of the products for each procedure.
Materials: electronic balance 2 test tubes evaporating dish
Bunsen burner tongs 250 mL beaker copper powder
goggles stirring rod scoop
sodium carbonate calcium nitrate vinegar
½ antacid tablet sodium bicarbonate balloon
Procedure: Part A Copper and Oxygen
1. Find and record the mass of the evaporating dish plus 3 grams of copper powder.
2. Place the evaporating dish containing the copper powder on the wire gauze.
3. Light the Bunsen burner and heat the evaporating dish for 10 minutes.
4. Turn off the burner, take the evaporating dish off the wire gauze and place on
the ceramic tile. Allow the evaporating dish to cool.
5. Place the evaporating dish with the copper oxide (substance in evaporating dish) on
the balance to find its mass and record.
6. Calculate the change in mass.
Part B Antacid and Water
1. Pour 70.0 mL of water in a 250 mL beaker.
2. Place the beaker with water on the balance. Also place the antacid tablet on the
balance. Find the mass of the beaker with water and the antacid tablet. Record your measurement in a data table.
3. Put the antacid tablet in the water. Watch to see when the chemical reaction is
complete.
4. After the reaction is complete, find the mass of the beaker and water again and record
the measurement in the data table.
5. Calculate the change in mass.
Part C Sodium Carbonate and Calcium Nitrate
1. Fill 1 test tube ¼ full of sodium carbonate solution and the other test tube ¼ full of
Calcium Nitrate.
2. Put the two test tubes in the beaker and find the mass of the beaker and test tubes.
Record the mass in a data table.
3. Pour the contents of the two test tubes into the beaker.
4. Find the mass of the beaker and contents along with the two empty test tubes and
record the measurement in the data table.
5. Calculate the change in mass.
Part D Vinegar and Sodium Bicarbonate
1. Fill a test tube about half full with vinegar.
2. Put about 1 scoop of sodium bicarbonate in the balloon.
3. Slide the balloon over the end of the test tube, being careful not to spill the sodium
bicarbonate into the vinegar.
4. Put the balloon and test tube in the beaker and find the mass of the beaker, balloon,
and test tube. Record your measurement in a data table.
5. Hold the balloon the shake the sodium bicarbonate into the vinegar.
6. When the reaction in complete, find the mass of the beaker, balloon, and test tube
again. Record your measurement in the data table.
7. Calculate the change in mass.
Conclusion: For each procedure compare the masses before the reaction to the masses after the
reaction and explain why there is a gain, a loss, or the two are equal. Include a discussion
of conservation of mass. If the before and after are not equal you must give specific,
scientific reasons why.