We know the process of Condensation-conversion from vapour to liquid at a given temperature. What's the conversion from gas to liquid at a given temperature called..? Doesn't this sound stupid? Like, what's the deal in calling a gas and vapour? Well, if you already know the answer, yeah, you are right. A gas never changes to liquid at a fixed temperature..! Condensation works by increasing the pressure so that matter changes to liquid, a more contained form. But on the other hand, a gas, irrespective of how much high pressure you apply, never reaches the liquid state. Does that mean we can never liquefy the gas? Of course, it's absurd. We have to control the other parameter, temperature. You reduce the temperature, and yeah, it changes to a liquid. To give you a little more info, the temperature, after which we can never liquefy, is called "Critical Temperature." Above the critical temperature, we ca...