The process by which water changes from liquid to gas is called evaporation. This occurs when water molecules at the surface gain enough energy, usually from heat, to escape into the air as water vapor. Evaporation is a crucial part of the water cycle, facilitating the transfer of water from oceans, lakes, and rivers into the atmosphere. Factors such as temperature, air movement, and humidity influence the rate of evaporation. It's essential for weather patterns, agricultural practices, and maintaining the overall balance of ecosystems by contributing to precipitation when the vapor condenses back into water.