Brownian Motion
- Brownian motion of particles is the phenomenon when:
Small particles (such as pollen or smoke particles) suspended in a liquid or gas are observed to move around in a random, erratic fashion
Brownian motion is the erratic motion of small particles when observed through a microscope
- Brownian motion:
- Can be observed under a microscope
- Provides evidence for the existence of molecules in a gas or liquids
- The particles are said to be in random motion, this means that they have:
- A range of speeds
- No preferred direction of movement
- The observable particles in Brownian motion are significantly bigger than the molecules that cause the motion
- In most cases, these were observed as smoke particles in air
- The air particles cause the observable motion of the smoke particles that we see
- This means that the air particles were small and light and the smoke particles were large and heavy
- The collisions cause larger particles to change their speed and directions randomly
- This effect provides important evidence concerning the behaviour of molecules in a gas, especially the concept of pressure
- The small molecules are able to affect the larger particles in this way because:
- They are travelling at a speed much higher than the larger particles
- They have a lot of momentum, which they transfer to the larger particles when they collide
