$(a)$ 'Evaporation causes cooling'. Comment on this statement.
$(b)$ Explain how water kept in an earthen pot becomes cool during summer?

(N/A) During the process of evaporation,the particles of the liquid absorb energy from the surroundings to overcome the force of attraction and change into the vapour state. This absorption of energy from the surroundings makes the surroundings cold.
$(b)$ An earthen pot has a large number of extremely small pores on its surface. Water continuously seeps out through these pores and evaporates. The energy required for this evaporation is taken from the remaining water inside the pot. As the heat is lost from the water,it cools down.