Particle model — Describe

What is Brownian motion, and how is it explained in terms of particles?

Brownian motion is the random, continuous, zig-zag movement of small visible particles (such as smoke particles in air or pollen grains in water). It occurs because the much smaller, fast-moving, invisible particles of the surrounding gas or liquid collide randomly and unevenly with the visible particle from all sides, causing it to be pushed in random, changing directions. This provides evidence that gas and liquid particles are in constant, random motion.