CBSE Class 9 Answered

(a) The particles of water attract one another with intermolecular forces of attraction and these forces hold the particles together in the liquid state. The heat which we supply to water during boiling is used to overcome these forces of attraction between the particles so that they become totally free and change into a gas. This latent heat does not increase the kinetic energy of water particles and hence no rise in temperature takes place during the boiling of water.

(b) When a little of spirit is put on our hand, the spirit evaporates rapidly by taking the required latent heat of vaporisation to change from liquid state to vapour state from our hand. So, our hand loses this heat to spirit and gets cooled.