Raising the temperature of a gas causes the gas to fill a greater volume as long as pressure remains constant. Gases expand at a constant rate as temperature increases, and the rate of expansion is similar for all gases. Charles's law (also called Gay-Lussac’s law) describes the relationship between volume and temperature of an enclosed gas. The law says that at constant pressure, the volume of a fixed number of particles of gas is directly proportional to the absolute (Kelvin) temperature, mathematically expressed as:
V = k T
where T is temperature on the Kelvin scale (see Temperature: Temperature Scales). If the temperature of a given amount of gas is doubled, for example, its volume will also double (as long as pressure remains unchanged).
