Explain the following phenomenon given reason :
(i) Tnndall effect.
(ii) Brownian movement.
(iii) Physical adsorption decreases with increase in temperature.

Explanation

(i) Tyndall effect : Scattering of light by the colloidal particles present in colloidal sol. Tyndall effect is observed only when the diameter of dispersed particles is not much smaller as compared to the wavelength of the light used and there is large difference in the refractive indiaes of dispersed phase and dispersion medium. Due to that calloidal particles show Tyndall effect becuse their particle size lies in the range of `(10A^(@)-10000A^(@)).`
(ii) Brownian movement : Continuous zig-zag movement of colloidal particales in a colloidal sol is called Brownian movement. The reason for Brownian movenent is based on the fact that the molecules of dispersion medium due to their kinetic motion strike against the Colloidal Particles from all sides with different forces. The resultant force cuased them to move.
(iii) Physiisoption is an exothermic process
`underset("adsorbent")("Solid")+underset("adsorbate")(Gas)hArr"Gas/Solid + Heat"`
According to Le Chatelier's Principle, if we increase the temperature, equilibrium will shift in the backward direction, i.e., gas is released from the surface on which it is absorbed.