Conservation of Matter/Mass
Matter cannot be created or destroyed by a chemical change. This very important
principle is known as the Law of Conservation of matter. This law applies to ordinary
chemical reactions (as opposed to nuclear reactions, where matter may be changed to
energy). During a chemical change, the atoms of one or more substances simply undergo
some rearrangements. The result of these rearrangements is the formation of new,
different substances. All of the original atoms are still present. It is because of the Law
of Conservation of Matter that we are able to write balanced chemical equations. Such
equations make it possible to predict the masses of reactants and products that will be
involved in a chemical reaction.
In this experiment, aqueous solutions of three different compounds will be used to
produces two separated and distinct chemical reactions. The fact that change occurs
during each reaction will be readily observable. The combined masses of the three
solutions (and their containers will be measured before and after each reaction has
occurred. This experiment should give you a better understanding of the Law of
Conservation of Matter and its importance in chemistry.
Purpose: to determine experimentally if mass is conserved in a particular set of chemical
reactions.
Procedure:
1. In a graduated cylinder measure exactly 10.0mL of sodium carbonate(Na2CO3)
solution. Pour into a clean dry 250 mL Erlenmeyer flask. Stopper the flask.
Rinse and dry the graduated cylinder.
2. Measure exactly 3.0mL of calcium chloride(CaCl2) solution and pour into a clean,
dry test tube. Stopper and label the tube.
3. Rinse and dry the graduated cylinder.
4. Repeat step 2 with 3.0 mL of sulfuric acid (H2SO4)solution.
5. Place the stoppered flask and the test tubes together on the balance. Record the
combined mass of these containers, stoppers, and solutions. This will be mass A.
in your data table.
6. Remove the flask and the test tube containing calcium chloride. Pour the calcium
chloride into the sodium carbonate in the Erlenmeyer flask. Swirl the flask to
thoroughly mix the two solutions.
7. Replace the stoppers in their containers and remass all three containers, even the
empty one. Record as mass B in data table.
8. Remove the flask and test tube containing sulfuric acid and carefully pour into the
flask. Leave the flask unstoppered. Feel the bottom of the flask while you
are swirling. Once all the bubbling stops, add the stopper
9. remass all three containers, even the empty ones..record as mass C in your data
table.
10. Thoroughly clean and rinse the flask Use your test tube brush and plenty of water.
Clean both test tubes and rinse with plenty of water.
Questions:
1. What indications that a chemical reaction was taking place did you observe in
procedure 5? Procedure 8?
2. Why were you instructed to leave the stopper off in step 8? What might have
happened if you did not?
3. Compare masses a, b, and c. Account for any differences.
4. In your opinion, does this experiment verify the Law of Conservation of Matter?
How might the experiment be improved?