Dancing grapes

Sparkling water was originally used to make water last longer on long sea voyages. However, sparkling water also has a rather amusing side effect: when you dip something in it, air bubbles (actually CO2 bubbles) form on it and if the objects are light enough, the additional air cushion causes them to rise. When ascending, however, many bubbles detach themselves from the objects and these have then less buoyancy. This causes the objects to sink again. There, additional bubbles form on their surface and the objects dance up and down as a result.

Materials you need for this experiment:

grapes	Instead of grapes you could also use various other objects. However the effect works best, if their density is similar to the density of water (grapes have the advantage that they are basically water and therefore have a very similar density to water).
glass	A glass of water or another transparent container is needed to put the water and grapes in it
sparkling water	The more CO2 is solved in the water (the more sparkling), the better the effect.

How to do the experiment:

	Put some grapes in a glass or transparent container.
	Add sparkling water in the glass.
	The grapes will dance up and down.

Try different objects. Which dance fastest? How does the surface of your objects influence the speed of the up and down movement? Can you find objects that normaly don't float in water but where the few CO2 bubbles from sparkling water are sufficient to keep them permanently at the surface?

Have fun experimenting!