Elementary Gas Laws:
Boyle's Law

Robert Boyle (1627-1691)
Birth: 1660, Ireland
Published book on Gases: 1680.
"The Sceptical Chymist"

Boyle studied the compressibility of gases in 1660. In his experiments he observed "At a fixed temperature, the volume of a gas is inversely proportional to the pressure exerted by the gas." The experiment is simple: (see figure on left)

A cylinder with a piston and a gas is immersed in a bath (e.g. water). The purpose of the bath is to have a ready heat source to maintain the temperature of the gas constant throughout the experiment. A mass is placed on top of the piston which results in a pressure on the gas. The gas volume is measured and 1/V vs P data point plotted. The mass is increased and the new 1/V vs P data point plotted. This is continued over several larger masses. to see what happens place the mouse cursor over the image.

The straight line implies


Which is Boyle's law.

Example: In the experiment above the initial volume and pressure of the gas is 2L, 3 atm. Assuming the temperature and moles of gas is constant, what is the pressure if the volume is reduced to 1.25 L? Let P1 and V1 be the initial pressure and volume and let P2, V2 be the final pressure and volume. Then according to Boyle's law,

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C101 Class Notes
Prof. N. De Leon