How does the water kept in an earthen pot (matka) become cool during summer?

Q.:- How does the water kept in an earthen pot (matka) become cool during summer?

 

Answer:-

An earthen pot (matka) has many small pores. Water seeps out through them and evaporates from the surface of the pot. The energy needed for evaporation is taken from the water kept in the earthen pot. As a result, water kept in earthen pot becomes cool.