Supercharge your learning!

Use adaptive quiz-based learning to study this topic faster and more effectively.

Brownian motion

Brownian motion is the random movement of particles suspended in a fluid (a liquid or a gas).

The discovery of Brownian motion served as important evidence for the kinetic model of matter:

Observation: When viewed through a microscope, particles of smoke or pollen in air do not stand still but instead are in constant motion in jerky randomly changing directions.

Explanation: The air must be made up of many tiny particles which are colliding with the smoke particles. These collisions cause the random motion of the dust particle.

Brownian motion of a big dust particle that collides with a large number of smaller air molecules.
Brownian motion of a big dust particle that collides with a large number of smaller air molecules.
A dust particle undergoing Brownian motion due to collisions with smaller air molecules. The random line is the path taken by the dust particle.
A dust particle undergoing Brownian motion due to collisions with smaller air molecules. The random line is the path taken by the dust particle.