Lord Kelvin (William Thompson)

Temperature Scales (Lord Kelvin)

At the beginning of the 1800s, a relationship was discovered between the volume and the temperature of a gas. This relationship suggests that the volume of a gas should become zero at a temperature of -273.15oC. In 1848 the British physicist William Thompson, who later became Lord Kelvin, suggested that this observation could be used as the basis for an absolute temperature scale. On the Kelvin scale, absolute zero (0 K) is the temperature at which the volume of a gas becomes zero. It is therefore the lowest possible temperature, or the absolute zero on any temperature scale. Zero on the Kelvin scale is therefore -273.15oC.

0 K = -273.15oC

Each unit on this scale, or each kelvin, is equal to 1 degree on the Celsius scale. There is a subtle difference between the units on these scales, however. Because the Celsius scale is based on two arbitrary references points, the difference between the temperatures of these two points is divided into degrees. The Kelvin scale, however, is an absolute scale. Zero is not arbitrarily defined; it is the lowest possible temperature that can be achieved. Thus, temperatures on the Kelvin scale are not divided into degrees. Temperatures on this scale are reported in units of "kelvin," not in "degrees kelvin."