Question

How can you show that water vapour is present in air?

Answer 1

To demonstrate the presence of water vapour in air, take some ice cubes in a glass. Let the glass stand without being disturbed for some time. You will observe droplets of water on the outer surface of the glass.
These water droplets result from the condensation of water vapour from the air on the cold surface of the glass. This shows that water vapour is present in air.