Question

Why do we regard the gaseous state of water as vapours while that of ammonia a gas?

Answer 1

Explanation:

Only the gaseous states of those substances are regarded as vapours which are liquid at room temperature. Since water is a liquid, its gaseous state is called vapours. However, the gaseous state of ammonia is called gas because it is not a liquid at room temperature.

Answer 2

Main difference between a vapour and a gas is

A substance that exists in its gaseous state at room temperature is a gas

IN THE PERIODIC TABLE WE HAVE 18 GASES

Whereas a substance that otherwise at the room temperature exists as a liquid or solid but is made to change into its gaseous state with the help of suitable conditions of temperature and pressure is a vapour

WE CAN HAVE VAPOURS OF ANY SUBSTANCE WITH HELP OF TEMPERATURE AND PRESSURE (we even have sodium vapours)

Hence water in its steam form is a vapour whereas ammonia is a gas

Hope it helps