Effect of Temperature

The effect of temperature on deviations of gas can be studied from the graph between compressibility factor and pressure at different temperatures for a particular gas say Nitrogen (N₂).

From the graph, it is observed that the deviation from Ideal behaviour is quite large at low temperatures. But as the temperatures is increased, the dip in the curve becomes lesser and lesser. In other words, the deviation goes on decreasing as temperature increases. However, at a certain temperature the value of ‘z’ remains close to one over an appreciable range of pressure i.e. the gas shows Ideal behaviour. For example, in case of nitrogen gas at 50°c it shows nearly Ideal behaviour (close to Ideal gas line) upto nearly 100 atm.

This temperature at which a real gas behaves like an Ideal gas over an appreciable pressure range is called Boyle Temperature or Boyle Point because at this temperature Boyle’s law is obeyed over an appreciable pressure range.