By Contributor | Updated Mar 24, 2022
Diffusion is the spontaneous movement of molecules from an area of higher concentration to an area of lower concentration, driven by their inherent kinetic energy. Over time, this process equalizes concentrations without the need for a catalyst, relying solely on the internal energy of the molecules themselves.
All molecules possess internal energy that manifests as random, microscopic motion. Even in a still-looking bath of water, the molecules inside are traveling at hundreds of feet per second. The rate at which diffusion occurs depends on this internal energy and the specific properties of each substance.
Consider a sealed container divided by a removable barrier. On one side, carbon monoxide (CO) is present; on the other, oxygen (O₂). While the barrier remains, the gases are immobile at the macroscopic level but their molecules constantly collide with the barrier. Once the barrier is removed, the molecules begin to mix, moving from the CO-rich side toward the O₂-rich side. Eventually, the entire container becomes a homogeneous mixture, in this case forming carbon dioxide (CO₂) as the gases react.
