Diffusion is the process by which atoms, molecules and other particles randomly blend together as a result of their kinetic energy. In general this leads to a phenomena where they move from an area of high concentration to an area of low concentration. Several factors that affect the rate of diffusion include temperature, density of the diffusing substance, medium of diffusion and concentration gradient
As temperature increases the average kinetic energy of particles increases. Greater kinetic energies lead to increased velocities. The increased velocity means that there is a greater chance of collisions between particles, resulting in an increased rate of diffusion. Generally, the rate of diffusion increases with temperature.
Density of the Diffusing Substance
Density is defined as the amount of material that exists within a given volume. Regions of high density contain a greater number of particles per unit volume than regions of lower density. An increased number of particles leads to a greater chance of collisions, and this leads to an increased rate of diffusion. A lower number of particles leads to a reduced chance of collisions and this lowers the rate of diffusion. Therefore, high-density regions have a greater rate of diffusion than low-density regions.
Medium of Diffusion
Diffusion also depends upon the medium in which it takes place. Physically, the particles within the medium act as a barrier to diffusion. Collisions between diffusing particles and the molecules of the medium lead to a reduction in the rate of diffusion. This means that the greater the number of molecules or larger particles within the medium, the lower the rate of diffusion.
The concentration of a substance is defined as the number of solute molecules that can be found within a given volume. Volumes of high concentration gradient have a large difference in the concentration of molecules over a unit length. A large difference in concentration leads to a greater probability of molecular collisions over the region and therefore increases the rate of diffusion. Generally, the greater the concentration gradient, the greater the rate of diffusion.