Question

explain why particles of colloidal solution do not Settle Down When left undisturbed, while in the case of suspension they do

Answer 1

It is because this particle size of colloidal sol.is much smaller than suspension sol.

Answer 2

In a colloidal solution the colloidal particles are small and they are being continuously hit upon by the molecules of depression medium.

It is very unlikely that the dispersed face particles will be hit upon by an equal force from all the sides.

Therefore there is a resultant force acting upon the colloidal particles in a particular direction.

And colloidal particles execute zigzag motion called Brownian movement.

Because of this the colloidal particles do not settle down under the influence of gravity.