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

Colloid particles resist settling rapidly to the bottom of a vessel due to Brownian motion. Brownian motion is the random movement of colloidal particles suspended in a liquid or gas, caused by collisions with molecules of the surrounding medium. The particles in colloids are in constant motion. It has strong intermolecular forces of attraction between the particles. But, in a suspension, the particles are bigger than that of a colloid and also molecular interaction in a suspension is not strong enough to keep the particles suspended, and hence they settle down.