The phenomenon of accumulation of the molecules of a substance on a solid or liquid surface resulting in the increased concentration of the molecules on the surface is called adsorption. In absorption, the substance is uniformly distributed throughout the bulk of the solution. A distinction can be made by taking an example of water vapours. Water vapours are absorbed by anhydrous calcium chloride but adsorbed by silica gel.
It is a surface phenomenon, i.e.,it occurs only on the adsorbentsurface.
It occurs throughout the bodyof the material. It is called bulkphenomenon.
The concentration on theadsorbent’s surface is differentfrom that in the bulk.