View Full Version : Brownian Motion Demonstration
02-12-2005, 09:37 AM
I'm wondering if anyone can suggest what to use to demonstrate Brownian Movement.
Is there any substance that could be introduced into a glass-sided water tank which would visibly create the effect for several hours (or longer!)?
It's for a science/art crossover thing for Einstein Year...
There is a substance called lycopodium powder which is, I believe, spores from a fungus. A small amount of that mixed into some water, then dropped onto a slide can illustrate it. I've also used chalk dust. I think it must have been artificial blackboard chalk, vs. calcium carbonate chalk, but I'm not sure. But I'm talking about a microscopic direct viewing of Brownian motion's effects. Maybe you could use a microprojector to show that on a large screen. As to the large scale version, I'm thinking about those cages that they draw the lottery ping pong balls from. It's not actually Brownian motion, per se, but you could color one ball and watch its more or less random motions in a mock up of one of those machines. One of my 8th grade students made one once, using a hair dryer as the engine. Not impossible. And, of course, you could always just drop a crystal or two - or many - of Potassium permanganate into the water. It would take a good amount of time, but after a while, you'd see the purple of the mineral diffusing through out the tank. That's simply the result of Brownian motion of the water molecules banging up against the crystals. THis may be the cleanest and most dramatic over time. xo C.
02-12-2005, 12:47 PM
lycopodium powder which is, I believe, spores from a fungus
Lycopodium powder comes not from fungus, but from Clubmoss (http://en.wikipedia.org/wiki/Club_Moss).
02-12-2005, 01:20 PM
A fresh cup of really Hot tea.
02-14-2005, 11:20 AM
Thanks for the responses, guys.
Potassium permanganate is a possibility but initial tests of this didn't look impressive enough apparently! Maybe trying again but using more might be better.
And, now that I've bumped this after the weekend, anyone else got any good Brownian Motion ideas?
02-14-2005, 10:46 PM
http://www.northstar.k12.ak.us/schools/joy/Science/demo4.html scroll down to the section on brownian motion and look at the picture. Perhaps you could do something like the soda bottle demonstration? Failing that, perhaps you could use talcum powder in your tank. It's easily obtainable and I would think it would look much more impressive than potassium permanganate.
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