Gases can be converted to liquids by compressing the gas at a suitable temperature.
Gases become more difficult to liquefy as the temperature increases because the kinetic energies of the particles that make up the gas also increase.
|Microscopic view of a gas.||Microscopic view of a liquid.|
The critical temperature of a substance is the temperature at and above which vapor of the substance cannot be liquefied, no matter how much pressure is applied.
Every substance has a critical temperature. Some examples are shown below.
|substance||critical temperature (oC)|
|Tubes containing water at several temperatures. Note that at or above 374oC (the critical temperature for water), only water vapor exists in the tube.|
|substance||critical pressure (atm)|