During evaporation, water is not turning into a gas or steam, but random movement of molecules on the surface of water provides some of the molecules enough energy to escape from the surface into the air. Evaporation takes place only on the surface of the body of water.
How long does it take for the water to evaporate?
According to these web sites, the average time a water molecule spends in the atmosphere is 8-9 days. This is pretty fast! So on average, it takes just 8-9 days for a water molecule to evaporate, enter the atmosphere, and then leave it again as rain.
How does water evaporate?
When liquid water meets dry air, it is not in equilibrium; water molecules evaporate off the surface until the amount of water in the air creates enough vapour pressure to achieve equilibrium. When water is heated to a temperature of 100C, the vapour pressure equals that of sea-level air pressure.