Name _______________________________________ Date _________________________ Period _____
Conservation of Mass
Question: Will the mass be conserved, the same for the products of a reaction as it was for the
reactants (beginning and end), during a typical chemical reaction?
Materials: balance, baking soda, 150, 400 ml beakers, 100 ml graduated cylinder, zipper-type sandwich
bag, vinegar
Procedure:
1. Place a piece of weighing paper on the balance. Put 4.0 grams of baking soda on the paper.
Carefully transfer the baking soda to the 400 ml beaker.
2. Using the graduated cylinder, measure 50 ml of vinegar into the 150 ml beaker.
3. Place both beakers, and plastic bag on the balance, and determine the combined mass of the
beakers, plastic bag, baking soda, and vinegar to the nearest 0.01 g. Record the combined mass
in your data table as the initial mass.
4. Take the beakers and plastic bag off the balance. Carefully place the beakers into the plastic bag
so that they don’t spill. Close the plastic bag tightly.
5. Tip the beakers over so that all of the vinegar mixes with all the baking soda. Observe the
reaction until it is completely finished. Do not open the bag.
6. Place the bag and all of its contents on the balance. Record the mass to the nearest 0.01 g in the
data table as the final mass.
7. Subtract the initial mass from the final mass and record the difference as the Change in Mass.
8. Rinse out the beakers and the plastic bag and was everything down the sink with plenty of water.
9. Repeat steps 1 and 2.
10. Place both beakers and their contents on the balance. Find the mass to the nearest 0.01 g and
record it as the initial mass.
11. Pour the vinegar into the 400 ml beaker and mix it with the baking soda.
12. Wait until the reaction is completely finished and then put both beakers on the balance. Find the
mass to the nearest 0.01 g and record in the data table as the final mass.
13. Repeat step 7.
14. Clean out both beakers and wash everything down the sink with plenty of water. Put everything
away.
15. Wash your hands.
Data:
Initial Mass (g)
Final Mass (g)
Change in Mass (g)
Trial 1
Trial 2
Observations
Calculations
Conclusion:
1. Compare the changes in mass that you calculated for the first and second trials. What value
would you expect to get for a change in mass if both trials validated t6he law of conservation of
mass?
2. Was the law of conservation of mass violated in the either trial? How do you know?
3. Suppose someone performs a similar (not identical) experiment in trial 2 and finds that the final
mass is much less than the initial mass. Would that prove the law of conservation of mass
wrong? Why?