Critical Temperature and Pressure (original) (raw)

Critical Temperature and Pressure

Critical Temperature

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.

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.

Tubes containing water at several temperatures. Note that at or above 374oC (the critical temperature for water), only water vapor exists in the tube.

Critical Pressure

The critical pressure of a substance is the pressure required to liquefy a gas at its critical temperature. Some examples are shown below.