What is condensation?
Condensation is the process by which a gas turns into a liquid, usually when it cools. Water vapor condensing forms clouds, dew and the droplets on a cold glass.
Air contains invisible water vapor. When warm, moist air touches a cold surface or cools as it rises, its water molecules slow down and clump together into tiny liquid droplets. Condensation is the opposite of evaporation and releases heat into the surroundings.
You can see condensation every day: water droplets forming on the outside of a cold drink, fog on a bathroom mirror after a hot shower and dew on grass on cool mornings. Your breath becomes visible on cold days because the water vapor you breathe out condenses into a tiny cloud.
Condensation in nature and machines
In the atmosphere, condensation forms clouds and fog and is essential for rain. The temperature at which air becomes saturated and starts to condense is called the dew point. Air conditioners, refrigerators and power plants all rely on condensation to move heat around.
Did You Know?
The white trails behind high-flying planes, called contrails, form when hot, moist engine exhaust condenses and freezes in cold air.