Explain Liquefaction of Real Gas and Permanent Gas.

Explanation

Liquefaction of Real Gases : All the gases upon compression at constant temperature (isothermal compression) show the sasme behaviour as shown by carbon dioxide.
That gases should be cooled below their critical temperature for liquification. ..Critical temperature of a gas is highest temperature at which liquifaction of the gas first occurs...
Liquefaction of Permanent Gases : Permanent gases (i.e., gases which show continuous positive deviation in Z value) requires cooling as well as considerable compression. Compression brings the molecules in close vicinity and cooling slows down the movement of molecules.
Therefore, intermolecular interactions may hold the closely and slowly moving molecules together and the gas liquifies.