A U-Tube Experiment To Discover the Curve in Boyle's Law

A discovery-style experiment is described to enable introductory chemistry students to determine the pressure versus volume behavior of a gas over a wide pressure range to "discover" Boyle's Law. A small volume of air is trapped by water or mineral oil in the sealed end of a 10-mL graduated pipet that has been bent in the shape of a U. The external pressure is reduced using a water aspirator to expand the gas sample as far as possible. The volume of the gas as a function of pressure (measured with a Bourdon tube absolute pressure gauge) is recorded as air is leaked back into the system through a needle valve. The experiment overcomes some of the limitations of previous methods and offers opportunities for several levels of data analysis.