Brownian Motion

Brownian motion is observed when small visible particles (such as smoke particles or pollen grains) are suspended in a fluid. The particles move in random, jerky paths because they are bombarded unevenly by invisible fluid molecules from different directions.

This provides evidence for the kinetic particle model: it shows that fluid molecules exist, are in constant motion, and move randomly. At higher temperatures, the motion becomes more vigorous because the fluid molecules move faster.