Sometimes, an experiment can be very surprising. You see something weird happening and you want to understand what’s going on. This experiment, where raisins move around inside a drinking glass, is just like that.
Pour sparkling water into the drinking glass, until it’s half-full. Drop about ten raisins into the liquid.
Take a good look at what happens. Try to keep your eye on a few ‘active’ raisins.
Describe – out loud – what you see, hear and smell, as it’s happening. Then try to explain what’s going on.
What did you discover
You see some raisins moving up and down, but not all of them. Raisins are dried grapes. Their skins are covered with water-repellent substances. This protects them against rain, for example.
The bubbles released from the carbonic acid in the mineral water do not dissolve well. Rather, they stick to the skin of the raisins. When enough bubbles stick to a raisin, it rises through the water. When the raisin hits the surface, the bubbles escape into the air. The raisin then sinks again. But on the way down, new gas bubbles stick to the raisin’s skin and the process repeats itself.