Name_______________________________________ Date ___________________ Section ________
Chemical Reactions and Mass Lab
Problem: How does the mass of the reactants (all the stuff before the reaction) compare to the mass of the
products (all the stuff after the reaction)? In other words, what happens to mass during a chemical reaction?
Hypothesis: ____________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
Variables:
Manipulated Variable: Mass before the reaction
Responding Variable: Mass after the reaction
Materials
• Triple Beam Balance
• 1 graduated cylinder
• 200 mL of tap water
• Scissors
• 1 Alka-seltzer tablet
• 1 large Ziploc bag
• 1 small Ziploc bag
Procedure
1. Place the Alka-Seltzer tablet into the small Ziploc bag, push any air out and seal it.
2. Measure about 200 mL of water in the beaker. Pour the water into the large Ziploc bag. If needed,
dry the outside of the bag with a paper towel.
3. Place the small Ziploc bag inside the large Ziploc bag. Push any air out and seal the large bag.
4. Place the large Ziploc bag (with the small one in it) on the balance. Record the mass as “mass before”.
5. Open the large bag; take out the small bag just enough to reach inside and cut the bottom corner of
the small bag. DO NOT LET THE ALKA-SELTZER TABLET FALL OUT AT THIS TIME. KEEP
THE CUT BAG CORNER IN THE LARGE BAG.
6. Press any air out of the large bag and SEAL THE LARGE ZIPLOC BAG COMPLETELY. Then
push the Alka-Seltzer tablet into the water through the hole cut in the small bag.
7. If needed, dry the outside of the large Ziploc bag and place the large Ziploc bag back on the balance.
Record the mass as “mass after.”
8. Make any observations of the contents of the bag.
9. Once observations and masses have been recorded, dispose of both bags and return any other
materials to where you found them.
10. Collect class data on before and after masses and record in a data table.
[Change in mass = mass after – mass before]
11. Answer the analysis questions.
Name_______________________________________ Date ___________________ Section ________
Observations:
_______________________________________________________________________________________
_______________________________________________________________________________________
Data Table
Group
Mass Before
(g)
Mass After
(g)
Change in Mass
(g)
1
2
3
4
5
6
7
8
9
Analysis Questions.
1. Why is it important to dry the outside of the large bag in Steps #2 and #7?
2. Why is it important to keep the cut corner from the small bag inside the large bag in Step #5?
3. What does the Law of Conservation of Mass (Matter) state?
4. Does any of the data above support the Law of Conservation of Mass (Matter)? Explain.
5. The results may show some errors. What are the possible sources of these errors? (List several)
Name_______________________________________ Date ___________________ Section ________
Data Table
1
Mass Before
(g)
195.2
Mass After
(g)
194.9
2
183
183
3
201
200
4
213.3
212.5
5
108.5
107
6
209
209
7
195
194.7
8
222.7
222
9
205.2
204.9
Group
Change in
Mass (g)
Analysis Questions.
1. Why is it important to dry the outside of the large bag in Steps #2 and #7?
2. Why is it important to keep the cut corner from the small bag inside the large bag in Step #5?
3. What does the Law of Conservation of Mass (Matter) state?
4. Does any of the data support the Law of Conservation of Mass (Matter)? Explain.
5. The results may show some errors. What are the possible sources of these errors? (List several)
Name_______________________________________ Date ___________________ Section ________
Chemical Reactions and Mass Lab
Problem: How does the mass of the reactants (before the reaction) compare to the
mass of the products (after the reaction)? In other words, what happens to mass
during a chemical reaction?
Hypothesis: It is hypothesized that ….because…
Variables:
Manipulated Variable: Mass before the reaction
Responding Variable: Mass after the reaction
Materials
• Electronic Balance
• 400 mL beaker
• 200 mL of water
• Scissors
• 1 Alka-seltzer tablet
• 1 large Ziploc bag
• 1 small Ziploc bag
Procedure
1. Place the Alka-Seltzer tablet half into the small Ziploc bag and seal it.
2. Measure about 200 mL of water in the beaker. Pour the water into the large
Ziploc bag. Dry the outside of the bag completely with a paper towel.
3. Place the small Ziploc bag inside the large Ziploc bag.
4. Place the large Ziploc bag (with the small on in it) on the balance. Record the
mass.
5. Open the large bag; take out the small bag just enough to reach inside and cut
the bottom corner of the small bag. DO NOT LET THE ALKA-SELTZER
TABLET FALL OUT AT THIS TIME. KEEP THE CUT BAG CORNER IN THE
LARGE BAG.
6. SEAL THE LARGE ZIPLOC BAG COMPLETELY. Then push the Alka-Seltzer
tablet into the water through the hole cut in the small bag.
7. Dry the outside of the large Ziploc bag and place the large Ziploc bag back on
the balance. Record the mass.
8. Make any observations of the contents of the bottle.
Name_______________________________________ Date ___________________ Section ________
9. Once observations and masses have been recorded, dispose of both bags and
return any reusable materials to where you found them.
10. Collect class data on before and after masses and record in a data table.
[Change in mass = mass after – mass before]
11. Construct a graph of the class data.
12. Answer the analysis questions.
Observations:
___________________________________________________________________
___________________________________________________________________
Data Table
Change in Mass = Mass After – Mass Before
Group
1
2
3
4
5
6
7
8
9
Mass Before
(g)
Mass After
(g)
Change in
Mass (g)
Name_______________________________________ Date ___________________ Section ________
Analysis Questions.
1. Why is it important to dry the bottle in Step #3?
2. Why is it important to mass the weighing dish or paper with the bottle in Step
#6?
3. What does the Law of Conservation of Mass state?
4. How does this lab support the Law of Conservation of Mass?
5. The results may show some minor errors. What are the possible sources of
these errors?
Name_______________________________________ Date ___________________ Section ________