Evaporation is what happens when a liquid turns into a gas or vapor, usually slowly and at the surface. When you leave a glass of water on the counter overnight, the water seems to disappear. It hasn't vanished: it evaporated into the air as invisible water vapor.

The sun's heat makes puddles evaporate after a rainstorm. Sweat evaporates from your skin on a hot day, cooling you down as it changes from liquid to gas. A wet towel hanging on a line slowly dries as water molecules escape into the air. The hotter it is, the faster evaporation happens.

Evaporation is different from boiling, which is when a liquid turns to gas rapidly throughout the whole liquid, creating bubbles. Water boils at 212°F (100°C), but it evaporates at any temperature, even on a cold day. That's why ice cubes slowly shrink in your freezer: the ice turns directly into vapor without melting first (a process called sublimation).

Evaporation is crucial to the water cycle that makes life on Earth possible. Water evaporates from oceans, lakes, and rivers, rises into the atmosphere, forms clouds, and eventually falls as rain or snow. Without evaporation, we wouldn't have fresh water or weather as we know it.