Explain the liquefaction of real gases and permanent gases.

(N/A) Liquefaction of Real Gases: All real gases,upon isothermal compression,exhibit behavior similar to $CO_2$. To liquefy a gas,it must be cooled below its critical temperature $(T_c)$. The critical temperature is defined as the highest temperature at which a gas can be liquefied by pressure alone.
Liquefaction of Permanent Gases: Permanent gases (gases that show continuous positive deviation in the compressibility factor $Z$) require both significant cooling and high compression. Compression brings molecules into close proximity,while cooling reduces their kinetic energy. Consequently,intermolecular forces become strong enough to hold the molecules together,leading to liquefaction.