The Kinetic Theory of Gases
James Clerk Maxwell (1831–1879) was born in Edinburgh, Scotland. He is the chief architect of the electromagnetic theory of light.1 Maxwell also played a significant role in the development of both thermodynamics and the kinetic theory of gases. Regarding the former topic (thermodynamics), Maxwell derived a set of four equations that relate changes in the thermodynamic variables of a substance.
Maxwell’s four thermodynamic relations are completely general in that they apply to any substance whatsoever.
Regarding the latter topic (the kinetic theory of gases) Maxwell argued that the macroscopic properties of a gas, like its pressure and temperature, may be understood in terms of the velocities of the molecules comprising the gas. The kinetic theory also provides a key to understanding phenomena such as the conduction of heat through iron, the viscosity of honey, and the diffusion of pollen through air. In the reading selection that follows, taken from his Theory of Heat, Maxwell provides an introduction to the kinetic theory of gases.