ABSTRACT
Figure 8.1 schematically shows the macroscopic results of the microscopic or atomistic processes of diffusion. The diffusion process sketched in Figure 8.1 is pure nitrogen and oxygen of equal amounts initially separated by some kind of barrier, and at t = 0, this barrier is removed without introducing convection allowing the gas molecules to diffuse into each other. In this case of nitrogen and hydrogen, as in all diffusion processes, the kinetic energy of the molecules is determined by the temperature. Even at room temperature, gas molecules have rapid thermal motion-speeds on the order of thousands of miles per hour-and they travel only about 0.1 μm before colliding with another gas molecule. So they experience over a billion scattering collisions per second, which leads to their mixing or randomization.
