Question

No heat is supplied to a liquid during evaporation. How does then the liquid change into its vapour$?$

Answer 1

Liquid molecules are in perpetual random motion and keep colliding with each other. When the liquid molecules collide with each other some particles acquire kinetic energy, and some lose their kinetic energy. By getting sufficient energy, some liquid molecules near the surface overcome the attractive forces of other molecules and escape from the surface. That’s how liquid changes into vapour even when no heat is supplied to it.