Question

Define the following terms with an example in each case:
(i) Macromolecular sol
(ii) Peptization
(iii) Emulsion

Answer 1

Macromolecule indicates a very large sized molecule. Peptization occurs because of the electrolyte added to a freshly precipitated substance. Emulsion is dispersion on one liquid into another liquid. One of them we call as dispersed phase and the other one as dispersion medium.

Complete Step by step answer: (i)The colloids in which the molecules having very large molecular mass strongly bond to each other with strong van der Waals forces is known as a macromolecular sol.
The macromolecular sols contain one large sized single molecule as a dispersed phase. Strong chemical bonds are present between the particles of macromolecular sols.
The examples of macromolecular sols are: Nylon, rubber, starch etc.
(ii)The process which helps in the formation of stable dispersion colloidal particles in dispersion medium is known as peptization.
The process in which a precipitate is converted into colloidal sol by shaking it with the dispersion medium in the presence of a small amount of electrolyte is known as peptization.
The process of peptization is used in the synthesis of nanoparticles.
The examples of peptization are: Ferric chloride added to the precipitate of ferric hydroxide so that the hydroxide precipitate transfers to the sol by absorbing ferric ions.
(iii)A fine dispersion of minute droplets of one liquid into another liquid in which it is not soluble is known as an emulsion.
Emulsions are of two types:
Oil in water emulsion: In these emulsions, oil is the dispersed phase and water is the continuous phase.
Water in oil emulsion: In these emulsions, water is the dispersed phase and oil is the continuous phase.
The examples of emulsion are: Milk, paints, smoke, etc.

Note: Lyophilic (fat loving) sols are macromolecular sols. The colloidal dispersion of natural macromolecules like starch, proteins, cellulose, gelatin, nucleic acids, etc. and synthetic polymers like polyethylene, polypropylene, etc. are macromolecular sols.