Explain why particles of a colloidal solution do not settle down when left undisturbed,while in the case of a suspension they do.

(N/A) The particles in a colloidal solution are very small (ranging from $1 \ nm$ to $1000 \ nm$) and remain in a state of continuous random motion known as Brownian motion. This motion,along with the electrostatic repulsion between charged colloidal particles,prevents them from settling down due to gravity. In contrast,particles in a suspension are much larger (greater than $1000 \ nm$). Because of their larger size,gravity acts more effectively on them,and the intermolecular forces are not sufficient to keep them suspended,causing them to settle down when left undisturbed.