Theory based on a simple description of a gas, from which many properties of gases can be derived. Established primarily by James Clerk Maxwell and Ludwig Boltzmann, the theory is one of the most important concepts in modern science. The simplest kinetic model is based on the assumptions that (1) a gas is composed of a large number of identical molecules moving in random directions, separated by distances that are large compared to their size; (2) the molecules undergo perfectly elastic (no energy loss) collisions with each other and with the walls of the container; and (3) the transfer of kinetic energy between molecules is heat. This model describes a perfect gas but is a reasonable approximation to a real gas. Using the kinetic theory, scientists can relate the independent motion of molecules of gases to their pressure, volume, temperature, viscosity, and heat conductivity.
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