Evaporation

From HydroWiki

Evaporation is the process in which the molecular bonds between liquid water molecules are broken through the addition of energy (primarily heat from the sun) which results in a phase transition to a gas or vapor. Evaporation is a key component of the hydrological cycle and is responsible for bringing over 90% of water vapor into the atmosphere. Source: http://ga.water.usgs.gov/edu/watercycleevaporation.html