Brownian Motion

Produced by the National STEM Learning Centre and Network and the Institute of Physics, this video illustrates how to show the movement of particles by Brownian motion. Instead of using the traditional smoke cell, the video shows how Brownian motion can be observed in a suspension containing micrometre diameter polystyrene spheres.

Using a microscope and video camera, students can observe the motion of the polystyrene spheres. The video also shows how Brownian motion can be simulated using a vibrating loudspeaker, table tennis balls and a small balloon.

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Carol Davenport

The (Whitley Bay) smoke cell takes a bit of practice to get to work. Although there is a certain amount of mystique in having the students troop through the darkened prep room to look down the microscope at the smoke particles, I think that this demo is more useful.


Nice clear demo. Only drawback is that it's with a liquid. Students have less of a problem with the idea of particles in a liquid sitting together, bobbling about (although some took a bit of persuading that the larger particle wasn't just floating on the water as the balloon is on the table tennis balls) than particles in a gas flying all around, which the smoke cell (tedioius & fiddly to set up) does.

Pennine lad

Nice demos. If can suggest another very easy to access material. Very, very dilute milk. Most whole milk is now homogenised and the fat globules are in the desired size range. In some respects milk shows more than the even sized micro-spheres in video as the student will also see that the smaller fat globules get jiggled around more than the larger and some are too large to b moved at all.

A normal flat slide (not cavity so an even thin layer), plus tiny drop of the dilute milk, and place a trace of vaseline around slip edges before placing on slide. this stops drying out.

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