Two different gases $A$ and $B$ are filled in separate containers of equal capacity under the same conditions of temperature and pressure. On increasing the pressure slightly,gas $A$ liquefies,but gas $B$ does not liquefy even on applying high pressure until it is cooled. Explain this phenomenon.

(N/A) The temperature above which a gas cannot be liquefied,no matter how much pressure is applied,is called the critical temperature $(T_c)$.
Gas $A$ liquefies upon a slight increase in pressure,which indicates that its temperature is already below its critical temperature $(T < T_c)$.
Gas $B$ does not liquefy even under high pressure unless it is cooled,which indicates that its temperature is currently above its critical temperature $(T > T_c)$. Cooling the gas brings its temperature below the critical temperature,allowing it to be liquefied by pressure.