* A Balloon, * A Ball, * A tank of water
Blow the balloon to the size of the ball. Then put the balloon and ball in a tank of water. Observe what happens to the ball and balloon in the water tank and note the difference. .
The gas filled balloon is lighter than a ball because air is lighter than the solid material used in the ball.
The balloon filled with gas sinks lesser than the ball of the same size. In some cases the ball may sink fully. The amount of water displaced is equal to the weight of the balloon or the ball. In some cases the ball may even sink.