Dancing Sultanas

What you need:

• sultanas or raisins
• sparkling water or lemonade
• a glass

What to do:

1. Fill the glass with sparkling water or lemonade.
2. Drop in several sultanas (small ones will work best).
3. Watch as the sultanas dance up and down in the water, floating and then sinking.

What happens:

The sparkling water has the gas carbon dioxide in it (CO₂). This is what causes the fizzing. When the sultanas are dropped in, little bubbles of carbon dioxide form on the surface, making the sultanas bigger, but not heavier. This causes the sultanas to be less dense than the water, causing them to float. Once they are at the top, the bubbles can pop, causing them to sink. This happens over and over again, until the drink goes flat and all the carbon dioxide is released.