Question

what is meant by air expands on heating

Answer 1

means if we gave heat then Kinetic energy were increased

Answer 2

Air expands on heating. Why does this happen? It is because the particles of air on becoming warm, move away from each other and take up more space. So we can say that air on becoming hot occupies more space. Since the particles move away from each other, the air becomes less dense and lighter in weight.

As a result, warm air rises up. On the contrary, on cooling the particles of air come closer to each other. Due to this, the volume of air becomes less, the air becomes more dense and heavier.