Author: David B. McWhorter
Book Description: The molecules in a gas are in constant, chaotic thermal motion. Because the molecules are free to move about, constituent molecules intermingle, collide with one another, and impinge upon particles that may be embedded in the gas. If the concentration of a particular constituent is non-uniform, there occurs an aggregate motion of that constituent from locations of high concentration toward locations of low concentration. This aggregate motion is diffusion and can be attributed to differences in partial pressure or chemical potential, as well as concentration.