Mottmann1 described an excellent way to measure the ratio of specific heats for air (γ = Cp/Cv) by suddenly compressing a plastic 2-liter bottle. His arrangement can be simplified so that no valves are involved and only a single connection needs to be made. This is done by adapting the plastic cap of a 2-liter plastic bottle so it connects directly to a Vernier Software Gas Pressure Sensor2 and the LabPro3 interface.

1.
J.
Mottmann
, “
Laboratory experiment for the ratio of specific heats of air
,”
Am J. Phys.
63
,
259
260
(March
1995
).
2.
Vernier Software; http://www.vernier.com, Item GPS-BTA.
3.
Vernier Software; http://www.vernier.com, Item LABPRO.
4.
Digi-Key; http://www.digikey.com, Item 738K-ND.
5.
Cole-Parmer; http://www.coleparmer.com, Item C-06405-02.
6.
Cole-Parmer; http://www.coleparmer.com, Item C-06359-31.
7.
D. F.
Krause
and
W. J.
Keeley
. “
Determining the heat capacity ratio for air from ‘almost adiabatic’ compressions
,”
Phys. Teach.
42
,
481
483
(Nov.
2004
).
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