Question

the desert sand is very hot in day and very cool at night explain the reason

Answer 1

Because sand cannot hold heat, it needs a constant source of energy to staywarm(The Sun). so during the nightwhen the sun is not shining the sandloses all its heat, making the desert night cold. Sand is the biggest reason why deserts are hot during the day and cold during the night.

Answer 2

The particles of liquid in desert cooler absorb energy from the surrounding to regain the energy lost during evaporation. In summer this is fast. Hence desert cooler cool better in a hot dry day.