Consider a surface of a liquid or a solid.
- The molecular forces at the surface of a liquid are unbalanced or in unsaturation state.
- In solids, the ions or molecules at the surface of a crystal do not have their forces satisfied by the close contact with other particles.
- Because of the unsaturation, solid and liquid surfaces tend to attract gases or dissolved substances with which they come in close contact. Thus, the substance accumulates on the surface of solid or liquid i.e., the substance gets adsorbed on the surface.
Hence,
Adsorption is a surface phenomenon.
