Question

Write short notes on the following: (i) Tyndall Effect
(ii) Brownian Movement
(iii) Coagulation

Hint:

The Tyndall effect helps differentiate colloids from true solutions, while Brownian movement provides evidence of the kinetic nature of particles.

Answer 1

(i) Tyndall Effect:
The Tyndall effect refers to the scattering of light by colloidal particles in a medium. When a beam of light passes through a colloidal solution, the particles scatter the light, making the path of the beam visible. This effect is used to distinguish between a true solution and a colloidal solution. The scattering is more intense in colloidal solutions due to the larger particle size compared to true solutions.
(ii) Brownian Movement:
Brownian movement is the random motion of particles suspended in a fluid (liquid or gas) due to collisions with molecules of the surrounding medium. This erratic movement was first observed by Robert Brown in 1827 and provides evidence of the kinetic nature of matter. The movement is more prominent in smaller particles and decreases as the size of the particles increases.
(iii) Coagulation:
Coagulation refers to the process in which colloidal particles aggregate to form larger particles. This occurs when the charges on the colloidal particles are neutralized or when the stability of the colloidal dispersion is disturbed, typically by adding an electrolyte. Coagulation can result in the separation of the colloidal particles from the dispersion medium, as seen in the formation of a precipitate.