Write a short note on liquefaction of gases.
For the liquefaction of gas, the condition should be so arranged that intermolecular attraction forces are increased and kinetic energy is decreased. If the pressure is sufficiently high and the temperature is lowered enough, the intermolecular attractive forces overcome the tendency of molecules to move apart and the gas molecules condense to the liquid state. Gases cannot be liquefied by pressure alone, they must be at the same time below their critical temperatures for this purposes. The following requirements are necessary for the liquefaction of gases:
(i) The gases should be pure and free from water vapours.
(ii) The temperature of the gas must be brought below its critical temperature.
(iii) The pressure applied must be great enough to cause the liquefaction.
