Brownian motion

Definition

Brownian motion is the random movement of particles suspended in a fluid (liquid or gas) resulting from their collision with fast-moving atoms or molecules in the fluid. It provides evidence for the existence of atoms and molecules.

5 Must Know Facts For Your Next Test

1. Brownian motion was first observed by botanist Robert Brown in 1827 while looking at pollen grains in water.
2. Albert Einstein provided a theoretical explanation for Brownian motion in 1905, which supported the atomic theory of matter.
3. The phenomenon is caused by collisions between the suspended particles and the molecules of the surrounding medium.
4. Brownian motion can be mathematically described through stochastic processes and diffusion equations.
5. Observations of Brownian motion helped to confirm the kinetic theory of gases, demonstrating that atoms and molecules are always in constant, random motion.

Review Questions

• Who first observed Brownian motion and when?
• What fundamental theory did Albert Einstein's explanation of Brownian motion support?
• Why do particles exhibit Brownian motion?

Related terms

Kinetic Theory of Gases:

A theory that describes a gas as a large number of small particles (atoms or molecules), all of which are in constant, random motion.

Diffusion:

The process by which particles spread from areas of high concentration to areas of low concentration due to random thermal motion.

Stochastic Process: A mathematical object usually defined as a collection of random variables representing an evolving system over time subject to inherent randomness.