Why does the air near the water's surface become cooler when water evaporates?

Answer 1

Because when evaporation occurs it removes sensible heat in the water and carries it off as latent heat in the water vapour. There is a loss of heat energy in the water making it feel cooler.

Answer 2

The water molecules within that pool of evaporating water have different "energies"-- some are moving faster than others. Temperature is just the AVERAGE kinetic energy of those molecules-- not all are the same temperature. SO, the molecules with more energy near the surface (essentially, the ones bouncing aroung faster-- moving faster-- "hotter" particles) are leaving the pool of water. This leaves the cooler molecules behind, so the average kinetic energy left in the pool (the temp) decreases as those "hotter" molecules escape.

Think about beans in a box with no lid-- you shake the box and faster beans escape.

also-- if the water is hot-- molecules are moving faster (greater ave kinetic energy), they move around, collide more. The water hits the glass of the thermometer, like a pool ball, the glass molecules are hit and move faster. The glass particles hit the Mercury in the thermometer. The Mercury moves faster ("heats up"-- more motion), the Murcury expands -- the thermometer reads an increase in temp.

Answer 3

When any material changes its state (in this case from the liquid state to the gaseous state), a certain amount of (thermal) energy is needed to make this change. With the water to vapor state, this amount of energy is (relatively) large, much larger than most materials. This is the reason that cities near large bodies of water have small temperature changes whereas in desert areas the temperature changes are large.