Explain the cause of Brownian motion

Question

Briefly define or explain the cause of Brownian motion?

Answer 1

Molecules in the gas move constantly, freely, arbitrarily, in all the directions and at high speeds. They are capable to do so as the intermolecular force of attraction among the molecules is negligible whenever in a gaseous state. This constant motion of molecules causes them to collide with everything in their path. For illustration, the dust particles will be bombarded through the molecules moving at high speeds, causing them to encompass a zigzag motion.

Brownian motion as well occurs in molecules in a liquid, however to a less obvious extent than in the gas.