Effects of Temperature and Pressure

Temperature Effects

The effect of temperature and pressure on a liquid can be described in terms of kinetic-molecular theory. The following figure illustrates the molecular behavior of a liquid at a low temperature near its freezing point and at a higher temperature near its boiling point.


Microscopic view of a liquid at a low temperature.	Microscopic view of a liquid at a high temperature.

Note how temperature effects the motion of the atoms or molecules in a liquid. As the temperature of a solid, liquid or gas increases, the particles move more rapidly. As the temperature falls, the particles slow down.

If a liquid is cooled sufficiently, it forms a solid.
If a liquid is heated sufficiently, it forms a gas.

Pressure Effects

Changes in presure have very little effect on the volume of a liquid. Liquids are relatively incompressible because any increase in pressure can only slightly reduce the distance between the closely packed molecules.

If the pressure above a liquid is increased sufficiently, the liquid forms a solid.
If the pressure above a liquid is decreased sufficiently, the liquid forms a gas.