The concepts of Newtonian mechanics, fluids, and ideal gas law physics are often treated as separate and isolated topics in the typical introductory college‐level physics course, especially in the laboratory setting. To bridge these subjects, a simple experiment was developed that utilizes computer‐based data acquisition sensors and a digital gram scale to estimate the molar mass of the gas in an inflated balloon. In this experiment, the comparable density of an inflated balloon to that of atmospheric air introduces a significant role for buoyancy that must be accounted for. The ideal gas law approximation is assumed for both the isolated gas mixture within the balloon and the surrounding air, which defines the relationship between the gas pressure, volume, temperature, and molar quantity. Analysis of the forces associated with the inflated balloon with the incorporation of Archimedes' principle and the ideal gas law into Newton's second law results in an experimental method for the measurement of the molar mass and mole fraction of a gas that is easy to implement yet academically challenging for students. The following narrative describes the basic setup of this experiment, along with a sample set of data as acquired and analyzed by a typical physics student from one of my classes.

Topics
Ideal gas, Newtonian mechanics, Data acquisition, Chemical elements, Chemical properties, Education, Buoyancy
1.
Vernier Software & Technology, Beaverton, OR; www.vernier.com.
2.
S. S. Zumdahl, Chemistry Principles, 3rd ed. (Houghton Mifflin Publishing Co., Inc., Boston, 1998), p. 172 (Table 5‐4).
3.
Worthington Cylinders, Columbus, OH; www.balloontime.com.
4.
B. A.
Jackson
 and
D J.
Crouse
, “
Experimentally determining the molar mass of carbon dioxide using a mylar balloon
,”
J. Chem. Educ.
73
,
997
(
1998
).
Google Scholar
 
5.
M. T.
Graham
, “
Investigating gases' masses in impecunious classes
,”
Phys. Teach.
40
,
144
–
147
(March
2002
).
Google Scholar
Crossref
Search ADS
 
6.
PASCO scientific, Roseville, CA; www.pasco.com.
7.
E. E.
Nalence
, “
Using automobile road test data
,”
Phys. Teach.
26
,
278ndash
;
279
(May
1988
).
Google Scholar
Crossref
Search ADS
 
8.
C. M.
Graney
, “
A treasure trove of physics from a common source ‐ Automobile acceleration data
,”
Phys. Teach.
43
,
506
–
509
(Nov.
2005
).
Google Scholar
Crossref
Search ADS
 
9.
F.
Solomon
 and
P.
Gluck
, “
An exercise in vehicle kinematics and energetics
,”
Phys. Teach.
47
,
137
–
141
(March
2009
).
Google Scholar
 
10.
In 2000, I developed an introductory physics experiment to measure the muzzle velocity of a Nerf gun using video capture technology. We have used this experiment at PCC Campus now for several years much to our students' delight.
This content is only available via PDF.
© 2010 American Association of Physics Teachers.
2010
American Association of Physics Teachers
AAPT members receive access to The Physics Teacher and the American Journal of Physics as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.