Question

explain why particles of a colloidal solution do not settle down when left undisturbed while in case of suspension they do

Answer 1

The colloidal practicals are smaller but not heavy. They always remain in state of zig-zag motion called Brownian movement, which counters the force of gravity acting on colloidal particles and hence , help in providing stability to colloidal sols by not allowing them to settle down . Apart from this, colloidal particles are charged and repel each other. While particles of suspension are larger and heavy and have less momentum , this settle down due to gravity .

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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.