Why does an evaporating liquid cool down according to the Kinetic Molecular Theory? Heat is required to evaporate a liquid. Heat is lost through elastic collisions. The highest velocity molecules are lost. Heat must be dissipated to break the liquid bonds.

3. The loss of high velocity molecule

Explanation:

Evaporation happens naturally when a liquid has a contact surface with surrounding environment and the environment is not saturated with liquid vapor. It happens due to that high velocity molecules/atoms is fast enough to overcome the intermolecular/atomic force that holds them together in liquid phase. This means that the liquid now has lower amount of fast atoms/molecule, and, according to Kinetic Molecular Theory, average kinetic energy of particles in the systems determine the temperature of the system. Thus, as high velocity particles escape, the average kinetic energy drops, which results in lower temperature

The highest velocity molecules are lost.

Explanation:

When liquid gets energy, its molecule kinetic energy increases. So molecules move so fastly, as result few highest velocity molecules breaks the forces and evaporates. Due to this removal, overall energy of the system become less which causes the liquid to be cool.