ABSTRACT
Diffusion is a spontaneous and random movement of molecules or particles in a fluid (gas or liquid) from a region of high concentration to a region of lower concentration. The difference in concentration between two such regions is called the concentration gradient. Diffusion occurs because particles in a liquid or gas are free to move according to the kinetic theory of matter. This phenomenon occurs simply because there are more diffusing molecules in the higher concentration region than in the lower one, and consequently, there is a net transfer from the lower to the higher concentration side as a result of random molecular motion. Transfer of heat from high temperature region to low temperature region provides an example of the diffusion process.
