What you need:
A rubber band, a small box, a small piece of cardboard, a few pins, a candle, a matchbox, a pair of scissors and a felt pen
What you do:
1. Put the rubber band around the box.
2. Cut out a cardboard arrow, put a pin through it and push the pin under the rubber band as shown in the picture.
3. Mark points A and B on the box.
4. Light the candle and bring it to point A of the rubber band. Next bring it to point B.
What happens?
When you bring the candle to point A, the arrow moves towards the left and when you move it to point B, it moves to the right.
Why does this happen?
The heat of the candle makes the rubber band contract at the point at which the heat is applied. When it contracts, the arrow turns to the left or right.
Unlike most things which expand when heated, rubber contracts when heated.
Picture Credit : Google
