Adsorption refers to which phenomenon?

• A. Dissolution
• B. Evaporation
• C. Adsorption
• D. Absorption

Answer: (C)

Adsorption is the process where molecules stick to a surface, accumulating at the interface rather than entering the interior of the material. This surface-based adhesion can be due to physical forces or chemical bonding, and it often depends on the surface area available for binding.

This distinguishes it from dissolution, where a solute disperses uniformly into a solvent to form a solution; from evaporation, where a liquid changes to a vapor phase; and from absorption, where a substance is taken up into the bulk of a material rather than staying at the surface. The surface-concentrating nature of adsorption is what makes it the correct phenomenon in this context.