The variation of pressure with temperature has been important in engineering since the advent of the steam engine. For an ideal gas, this is adequately described by the Universal Gas Law ( PV = nRT ), according to which pressure increases linearly with temperature for a sample of gas at fixed volume. However the Universal Gas Law does not apply to real gases close to liquification nor to liquids themselves. In both these circumstances intermolecular forces are very important, while the are negligible or small in most gases. In this experiment you will investigate how pressure varies with temperature in a system which includes interatomic forces.