Dancing Raisins

Make raisins dance in front of your eyes using nothing more sophisticated than some fizz.

What you need

	Raisins, currants, or something of a similar size and weight.		Some fizzy drink
	A large glass or jar

What to Do

What may Happen

You should find that the raisins dance up and down for several minutes until the drink goes flat.

What is going on?

Fizzy drinks are fizzy because they have had a lot of carbon-dioxide (CO₂) dissolved in them under pressure. When you release the pressure by opening the lid, this carbon-dioxide then comes out of the solution and forms bubbles. It is hard for gases to form bubbles in the centre of a glass of water because surface tension crushes them before they can grow large enough to be stable (Find out more in the lemonade volcano experiment). 

This means that bubbles tend to form on the edges of the water, ie on the bottom of the glass, and on your raisin. If you look carefully you can see them growing larger and larger.

Eventually the bubbles make the raisin float and it moves upwards to the surface, where some of the bubbles pop and the raisin sinks again.

Written by Dave Ansell