Question

Define the following terms giving an example of each:
(i) Associated colloids (ii) Lyophilic sol (iii) Adsorption

Answer 1

1. Associated Colloids (Micelles): Associated colloids are those colloids which behave as normal strong electrolytes at low concentrations but exhibit colloidal properties at higher concentrations due to the formation of aggregated particles. The aggregated particles thus formed are called micelles. The associated colloids are usually formed by surfactants (surface active agents) like soaps and synthetic detergents. These agents form micelles when present in solution at a concentration greater than critical micellization concentration (CMC).

2. Lyophilic colloids are formed by substances like gums, starch and proteins. Lyophilic sol can be easily prepared by directly mixing colloid with the liquid. They are very stable and do not precipitate/coagulate easily. However addition of very large quantities of electrolytes can cause particles to precipitate.

3. Adsorption is the adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface. This process creates a film of the adsorbate on the surface of the adsorbent.