How will you demonstrate that water vapour is present in air?
Take a dry glass and ensure it is dry from outside.
Now place a few ice cubes inside the glass.
Now wait for a few minutes.
You would observe droplets of water appear on the outside of the glass.
This takes place because of condensation.
So we can conclude that water vapour is present in air and when it comes in contact with cold objects changes into liquid form.
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