Water kept in an earthen pot (matka) becomes cool during summer due to the following reasons:

Porosity of Earthen Pot
Earthen pots are made up of clay which is porous in nature. The tiny pores in the clay allow the water to seep through and evaporate from the surface of the pot. This evaporation process causes a cooling effect on the water kept inside the pot.

Capillary Action
The clay used in earthen pots has capillary action. When water is poured into the pot, the clay absorbs the water and the water moves up through the pores of the clay due to capillary action. This upward movement of water helps in keeping the water cool.

Heat Absorption and Radiation
During summers, the temperature outside increases and the sun’s rays are stronger. The earthen pot absorbs the heat energy from the sun’s rays, and the temperature inside the pot increases. However, the water inside the pot does not get heated up because the heat energy absorbed by the pot is used to evaporate the water from the surface of the pot. This process of heat absorption and radiation helps in keeping the water cool.

Chemical Composition
Earthen pots are made up of clay which contains minerals like silica, alumina, and iron oxide. These minerals have the property of ionization which helps in purifying the water. The water stored in an earthen pot becomes alkaline in nature due to the presence of these minerals. Alkaline water has several health benefits like improving digestion and boosting immunity.

Conclusion
In conclusion, the water kept in an earthen pot (matka) becomes cool during summer due to the porosity of the pot, capillary action, heat absorption and radiation, and the chemical composition of the clay. Drinking water stored in an earthen pot is not only refreshing but also has several health benefits.

Bcoz it has holes between that which makes air easily come and out