ABSTRACT
Diffusion is one of the basic processes by which material moves. It is a result of continuous motion of atoms, molecules and particles moving from regions of high to low concentration. Besides, there are other processes that produce inhomogeneity, and the combined result of diffusion and other processes is generally not precisely defined. Diffusion depends on three main parameters: (i) temperature, (ii) mass (size) of the diffusing particles and (iii) viscosity of the system. While the temperature is a measure of the average kinetic energy, which is due to the movement of particles in the system, in most systems the energy is equal to a constant times the temperature, and a higher kinetic energy means a higher viscosity, yet the speed of diffusion always increases with temperature. Since heavy particles have a lower velocity for a given kinetic energy, they diffuse more slowly than lighter, smaller ones. Diffusion is most rapid in a gas, slower in a liquid, and very slow or almost zero in a solid.
