01. Why do we see water droplets on the outer surface of a glass containing ice-cold water?
We know that water vapour is present in the air. So when the air is passing through the glass the water vapour molecule comes in contact with the cold surface and losses energy. As when a substance losses energy it goes to its previous state so the water vapour goes to liquid state and we see water droplets on the outer surface on the glass.
2. Why the water kept in an earthen pot remains cold than the water in a normal pot?
The earthen pot has many small pores on its surface and very small amount of water comes out through these pores and gets evaporated. We know for evaporation some heat is needed. So the amount of heat energy is served as latent heat by the water of the pot. By loosing heat the water becomes cool. But normal pots don't have pores and the evaporation cannot happen.
3. Why do we feel cold if some spirit is applied on our skin?
The spirit gets evaporated by absorbing latent heat from our skin. By loosing heat that particular place of skin becomes cold.
4. Why can latent heat not change the temperature of the substance?
Temperature increases due to the increase of kinetic energy of a substance. But if kinetic energy is constant then the temperature will remain same. When a substance forms its liquid by absorbing latent heat there is no change in kinetic energy. So the temperature remains same only the state of matter is changed.
