Question

give reason a)steam produces more severe burns as compared to boiling water.
b)temperature of a liquid does not change when it boils.

Answer 1

b)when water is boiling, adding heat does not increase its temperature. This happens at the boiling temperature of every substance that can vaporize. At the boiling temperature, adding heat energy converts the liquid into a gas WITHOUT RAISING THE TEMPERATURE.
a)When steam condenses, it releases its massive heat of vaporization. At that point, it is just boiling water. The heat released by the steam all at once as it condenses is more than all the heat the boiling water will release in cooling down from 100°C to room temperature.

Answer 2

1) steam produces more severe burns as compared to boiling water because when steam condenses it releases the heat equal to latent heat of vaporisation which it had absorbed to change its state from water to vapour whereas the boiling water does not release any such heat because of which it does not produce any such severe burns
2) the temperature of a liquid does not change when it boils because the water absorbs heat provided (equal to latent heat of vaporisation) to change its state from water to vapour
hope this helps