Brownian MotionBrownian Motion

Thermal Physics Lesson 8Thermal Physics Lesson 8

Homework

Finish the past paper questions by next Friday (October 16th).

Learning Objectives

Describe evidence supporting the kinetic theory of gases.

Robert Brown (1773-1858)

In 1827, the botanist Robert Brown was looking at pollen grains in water.

He noticed that they constantly moved with a zigzag random motion.

Brownian Motion Experiment

We can observe Brownian motion in the lab.

We put smoke in a brightly lit glass jar and observe the particles using a microscope.

Observe bright specks moving haphazardly from side to side and up and down.

Brown couldn’t explain it…

Einstein used it 80 years later as evidence for the existence of molecules in the air.

The randomly moving molecules were hitting the smoke particles unevenly, causing the motion.