Question

a new earthenpot keeps water cooler than the old one why

Answer 1

these coz they have small pores that helps in keeping water cooler.

Answer 2

There are fine pores on the surface of new earthen pots. The water rises in these pores due to capillary action and spreads over the surface. The water from the surface of pot, when evaporates, cools down the pot and keeps the water cold. With time, the dust particles fill the capillaries of pot and hence the above phenomenon do not take place in old pots.