(a) Multimolecular colloid: Multimolecular colloidal solution consists of aggregates of atoms or small molecules with diameter less than 1 nm. e.g., gold sol.
Associated colloid: There are some substances which at low concentrations behave as normal strong electrolytes, but at higher concentrations exhibit colloidal behavoiur due to the formation of aggregates. The aggregated particles thus formed are called micelles. These are also known as associated colloid.
(b) Coagulation is the change in the state from colloidal to suspended colloidal paricles. Peptization is the convesrion of precipitate into colloidal sol by shaking it with dispersion medium in the presence of an electrolyte.
(c) Homogeneous catalysis is the reaction in which reactant and catalyst are in same phase.
Heterogeneous catalysis is the reaction in which reactant and catalyst are in different phase.