Question

When vapour is cooled it's changes into liquid why

Answer 1

bcz it is the process called condensation.....in this temp will remain constant untill and unless the the vapour has completely transitioned into liquid state

Answer 2

ANSWER:  

When vapor is cooled it changes into liquid because of the Condensation process that takes place due to cooling.

EXPLANATION:

When a vapor is cooled it loses its kinetic energy, so that constituent molecules will begin to associate by means of attractive forces thus resulting in Condensation process.

During this transition, the temperature remains same until the gas changes completely to the liquid state. This reaction is termed as an exothermic reaction because of the liberation of heat.