Question

Why is heat given out when a vapour condenses into a liquid ?

Answer 1

An exothermic reaction gives off heat energy. Condensation is the process by which water vapor turns into liquid water. This typically occurs when water vapor molecules come into contact with cooler molecules. This causes the water vapor molecules to lose some energy as heat. Once enough energy is lost, the water vapor changes state into liquid.
In condensation the latent heat of vapourization is given up at a constant temperature, the boiling point of liquid. so the heat is given out when a vapour condenses to a liquid