Question

Explain why particle of a colloidal solution do not settle down when left undisturbed, while in case of a suspension, they do?

Answer 1

Colloidal particles are smaller in size. They remain in state of zig-zag motion

(Brownian motion) always,

so the force of gravity is encountered and they do not settle down.

But the particles in suspension are larger in size,

so they settle down under the influence of gravity.