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What is responsible for Brownian motion?

1. Thermal agitation in the liquid
2. Convection currents in the liquid
3. Collisions of dispersion-medium molecules with colloidal particles
4. Attractive forces between colloidal particles and the molecules of the dispersion medium

Correct answer: Collisions of dispersion-medium molecules with colloidal particles

Solution

Brownian motion is the random zig-zag movement of colloidal particles due to collisions with molecules of the dispersion medium. Thermal agitation is the underlying reason, but the direct cause is the bombardment by medium molecules.

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