Describe an activity to demonstrate that warm air is lighter than cool air.
- Take two paper bags of the same size and hang them in inverted position on the two ends of a wooden stick.
- Tie a thread in the centre of the stick and hold the stick by the thread to balance it.
- Place a burning candle below one of the bags.
- The bag above the candle goes up, as the air above the candle becomes warm, it rises, and pushes the bag up.