Question

Distinguish between the meaning of the terms adsorption and absorption. Give one example of.

Distinguish between the meaning of the terms adsorption and absorption.

Answer 1

Adsorption is a surface phenomenon of accumulation of molecules of a substance at the surface rather than in the bulk of a solid or liquid. The substance that gets adsorbed is called the ‘adsorbate’ and the substance on whose surface the adsorption takes place is called the ‘adsorbent’. Here, the concentration of the adsorbate on the surface of the adsorbent increases. In adsorption, the substance gets concentrated at the surface only. It does not penetrate through the surface to the bulk of the solid or liquid. For example, when we dip a chalk stick into an ink solution, only its surface becomes coloured. If we break the chalk stick, it will be found to be white from inside.

On the other hand, the process of absorption is a bulk phenomenon. In absorption, the substance gets uniformly distributed throughout the bulk of the solid or liquid.

Answer 2

No.	Adsorption	Absorption
1.	Adsorption is a surface phenomenon as the adsorbed matter is concentrated only at the surface and does not penetrate through the surface to the bulk of adsorbent.	Absorption is a bulk phenomenon as the absorbed matter is uniformly distributed inside as well as at the surface of the bulk of a substance.
2.	The concentration of the adsorbate is high only at the surface of the adsorbent.	The concentration of the absorbate is uniform throughout the bulk of the absorbent.
3.	It is dependent on temperature and pressure.	It is independent of temperature and pressure.
4.	It is accompanied by the evolution of heat known as the heat of adsorption.	It may or may not be accompanied by evolution or absorption of heat.
5.	It depends on the surface area.	It is independent of surface area.
6.	Adsorption of a gas or liquid-like acetic acid by activated charcoal.	Absorption of water by cotton, absorption of ink by blotting paper.