Ahad, 27 Oktober 2013

Amali Sains: Kismis Menari

Mengapakah buah-buah kismis bergerak ke atas dan ke bawah secara berulang apabila  air minuman berkarbonat dituangkan ke dalam suatu cawan plastik lutsinar yang diiisi dengan 4-5 biji buah kismis?

The reason why the raisins dance in the club soda and then floats to the top is because the bubbles in the soda stick to the rough edges of the raisin making it more buoyant, meaning that it floats easily. The bubbles in the soda are carbon dioxide gas and help bring the raisins to the top, when the bubbles reach the top, they pop and release the carbon dioxide gas into the air. This makes the raisins fall back down again since it is denser than the liquid soda. The bubbles make the raisins float to the top similar to how a life jacket keeps you above water!

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. 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.