Describe an activity to demonstrate that warm air is lighter than cool air.

Activity:

1. Take two paper bags of the same size and hang them in inverted position on the two ends of a wooden stick.
2. Tie a thread in the centre of the stick and hold the stick by the thread to balance it.
3. Place a burning candle below one of the bags.
4. The bag above the candle goes up, as the air above the candle becomes warm, it rises, and pushes the bag up.
5.