Q. Assertion : All the gases should be cooled below their critical temperature for liquification.
Reason : Cooling slows down the movement of molecules therefore, intermolecular forces may hold the slowly moving molecules together and the gas liquifies.

 1515  215 States of Matter Report Error

Solution:

Critical temperature of a gas is the highest temperature at which liquification of the gas first occurs. Above critical temperature, gas cannot be liquefied howsoever high pressure may be applied on the gas.