CBSE Class 12 Chemistry Notes: Surface Chemistry – Some Important Properties

Colligative properties:- The properties of a solution which depends upon the no. of moles of solute particles present in the solution are called as colligative properties like osmotic pressure, elevation in boiling point etc.

Mechanical Properties:-

It does not depend upon the nature of the colloid but depends upon the size of colloidal particles and viscosity of the sol.

Cause of Brownian moment:- reason is the molecules of dispersion medium due to their kinetic motion strike against the colloidal particles from all sizes with different forces.

Optical properties [Tyndall effect]:- this effect may be defined as the scattering of light by the colloidal particles present in a colloidal sol.

The illuminated path of beam is called Tyndall effect cone. The phenomena is observed when a beam of light is projected in a cinema hall and it becomes visible due to scattering by colloidal dust particles.

Tyndall effect is observed only when following properties are satisfied:-

1. The diameter of the dispersed particles is not much smaller as compared to wavelength of light used.
2. There should be a large difference in refractive indices of dispersed phase and dispersion medium.

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