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