What is diffusion?

Diffusion is defined as the transfer of particles from an area of higher concentration to an area of lower concentration. This is because diffusion is a property of equilibrium. It means that diffusion tries to find a state of uniformity in which the particles are of equal concentration everywhere. This can only take place with liquid and gas particles as solid particles are unable to move.

However, when solids are raised to a temperature where they melt, they also exhibit the property of diffusion. An extension of this property to water molecules is called osmosis. Here, water particles travel from an area of high-water concentration to an area of low water concentration.