What is the difference between multimolecular and macromolecular colloids ? Give one example of each. How are associated colloids different from these two types of colloids?

Explanation

(i) Multimolecular colloids. These colloidal solution consists of aggregates of atoms or small molecules with diameter less than `10^3` pm. These atoms or molecules are held by weak van der Waal.s forces e.g ., colloidal solution of sulphur, gold, silver etc.
(ii) Macromolecular colloids. In these molecules of dispersed phase are of colloidal dimensions (`10^3 - 10^5` pm). These have very high molecular masses, e.g., colloidal solutions of proteins starches, gums etc.
(iii) Associated colloids (Micelles). These behave as normal, strong electrolytes at low concentration but show colloidal properties at higher concentrations i.e., these get associated to give micelles. e.g., soap. Formation of micelle takes place above a certain concentration called critical miceller concentration (CMC) and above a particular temperature called Kraft temperature `(T_k)`. When the solution has less concentration than CMC, it behaves as normal electrolyte as the micelle become unstable on dilution.
Difference between associated colloids and multimolecular and macromolecular colloids, Multimolecular colloids are formed by the aggregation of a large number of simple molecules (eg. `S_8`) whereas, macromolecular colloids are due to large size of the molecules themselves (e.g., starch) so large that their size lies in the colloidal range, e.g., soaps. This happens above a particular concentration (called critical micelle concentration) and above a particular temperature, called Kraft temperature.
Normal colloidal solutions (i.e., multimolecular or macromolecular) when diluted do not become a true solution like associated colloids or miscelles.