Question

How are colloids classified on the basis of the nature of interaction between a dispersed phase and a dispersion medium? Describe an important characterstic of each class. Which of the sols need stabilising agents for preservation?

Answer 1

Basing on the affinity between dispersed phase and dispersion medium, colloidal solutions are classified into Lyophilic Sols and Lyophobic Sol.

Lyophilic Colloids :-

• Colloidal solutions in which great affinity exists between the dispersed phase and dispersion medium are called lyophilic sols. (Lyo = liquid, Philic = affinity or love).

• These are solvent loving colloidal solutions.

• They are reversible colloids.

• They are prepared by direct mixing of dispersed phase and dispersion medium.

• The particles are solvated.

• These sols are quite stable and are not easily coagulated.

• Eg: Starch, Protein, Polymer solutions.

Lyophobic sols :-

• Colloidal solutions in which little (or) no affinity exists between the dispersed phase and dispersion medium are called lyophobic sols. (Lyo = liquid, Phobic = hate).

• These are solvent hating colloidal solutions.

• They qre irreversible colloids.

• They are not prepared by direct mixing of dispersed phase and dispersion medium.

• The particles are not solvated.

• Lyophobic sols need stabilising agents for their preservation.

• Eg: Gold sol, metal sols, sols of metal sulphides and oxides etc.

Answer 2

How are colloids classified on the basis of the nature of interaction between a dispersed phase and a dispersion medium? Describe an important characterstic of each class. Which of the sols need stabilising agents for preservation?