This month we combine raisins and a carbonated drink for some uplifting science.
What you need:
A handful of raisins
Tap water
Fresh soda water
A glass
What to do:
To start off, fill your glass to about 5cm from the top with regular tap water.
Gently drop your raisins into the glass one at a time. Watch as the raisins slowly sink down to the bottom of the glass. Pour out the tap water and remove the raisins. Now repeat the experiment, this time using the soda water in place of the tap water. What do you think will happen this time?
Why it works:
After watching, in amazement, as your raisins ‘danced’ up and down inside the glass of soda, you may be curious about why these dried fruits are putting on such a curious display.
The ‘dancing’ your raisins have been doing is really just a coordinated sequence of floating and sinking. Think back to the first experiment with the plain old tap water. We didn’t get to see any ‘dancing’ just a bunch of raisins sinking to the bottom of the glass. So why was it different when we used soda water?
Look again at your glass of dancing raisins. Do you see any bubbles in the soda water? Look for a bubble that is on the move and watch where it goes. Does it move up to the top of the glass or down to the bottom? Right, it moves up. Each bubble in the soda will float up to the surface of the water where it pops!
Take a really close look now at the raisins in the soda. Are there any bubbles sticking to their sides? Watch a raisin as it moves up to the top of the glass: it should be covered in bubbles. These little bubbles work like tiny life jackets for the raisin and when enough of them cover the raisin, it floats. Of course, when the raisin reaches the surface, the bubbles pop. The raisin has lost its life jacket so down it sinks and the whole dance starts again.
For more great things to discover – visit the Discovery Centre on Barrington Street in Halifax, check out their website or join them on facebook