The Conservation Of Mass (The Mass Of Gas)

Jake Carter Douglass Math and Science Academy
543 North Waller
Chicago IL 60644


This experiment will help students with their understanding of matter in
all of its phases. It will show that in a chemical reaction where a gas is
produced, the mass does not change. The mass does not change provided none of
the gas is allowed to escape. This will give evidence for conservation of
mass. In furthering their knowledge of the laws of conservation of mass, the
loss in mass can be accounted for, when the gas is allowed to escape from the
container which it is produced in. This will prove that gas does have mass.

Materials Needed:

Balance 1/8 Alka-Seltzer tablet
Pegboard and clamps (optional) Paper towel
Small, thick-walled bottle with Safety glasses
tight-fitting cap Tape


Students are asked to work with their lab partner to carry out this
experiment. The Students will collect all materials from the teacher's
material lab station in the front of the room. The students must return to
their lab stations to set up the apparatus. Now, begin by massing the small
thick-walled bottle, 3/4 full of water, the cap and the 1/8 piece of Alka-
Seltzer tablet on the balance. The initial massing of the bottle, cap, water,
and 1/8 piece of Alka-Seltzer tablet should be recorded on the sample data
The final massing of the small, thick-walled bottle, cap (put the Alka-
Seltzer table in the water) and solution should now be done. Record your
results on the data graph. To avoid any gas from escaping the students must
work quickly to drop the 1/8 Alka-Seltzer tablets into the bottle of water and
close the cap. Students should at this time compare data from the initial
massing with that of the final massing. The students are now ready to
complete the final part of the experiment. The cap on the bottle should be
loosened slowly, so that no water bubbles out when the gas escapes. When the
gas escapes, the solution shows a small change in mass. Record the data on the
data graph. The mass difference would suggest that:__________________________.
Repeat the entire experiment for a second time, record and compare results.

Performance Assessment:

1. The student will be able to communicate their results of the experiment
in a written lab report, using a standard lab reporting form.
2. They will be able to articulate the experiment in our post lab
3. Students will create a scientific graph showing results of the experiment.
4. Students will be able to draw conclusions about the conservation of matter
based upon the experiment.

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