The process when water turns into vapor is called evaporation. This occurs when liquid water is heated to a point where its molecules gain enough energy to transition into the gas phase. Evaporation can happen at any temperature, but it occurs more rapidly at higher temperatures. Factors such as surface area, air movement, and humidity can also influence the rate of evaporation. This process is a crucial part of the water cycle, contributing to the formation of clouds and precipitation as water vapor cools and condenses back into liquid.