Robert Boyle (1627-1691), a contemporary of Newton, experimented on gases and came to the conclusion that the volume V of a gas varies inversely with the pressure P at a fixed temperature. Thus, If we double the pressure, while holding both the temperature T and amount of substance n constant, the gas is reduced to one-half of its initial volume. The mathematical expression for this is

It was later shown by van der Waals (1837-1923) that this simple expression does not hold for high density gases or gases at low temperature and he was able to correct Boyle's law by assuming that the molecules of the gas interact through what are now called van der Waals forces. In extreme cases it is these forces that cause gases to liquify.

In this experiment you will investigate Boyle's law and see how system pressure depends on density (which is inversely related to the volume) at fixed temperature.