Question

Describe an experiment to show that air expands on heating.

Answer 1

(i) Take an empty bottle. Actually the empty bottle contains air. Attach a rubber balloon to its neck as shown in the following figure. Initially, the balloon is deflated.

(ii) Place the bottle in a water bath containing boiling water. After some time you will notice that the balloon gets inflated as shown in the following figure. The reason is that the air inside the bottle expands on heating and it fills the balloon.

Thermal expansion of air

(iii) Take the bottle out of the water bath and 7 allow it to cool by itself. We will notice that the balloon gets deflated and it collapses. This is because the air inside the balloon and the bottle have contracted on cooling. The air from the balloon passes to the bottle, so the balloon gets deflated.