Description: Clouds are water. As you probably know, we can find water in three forms: liquid, solid and gas. Water as a gas is called water vapor. Clouds form when water vapor turns back into liquid water droplets. That is called condensation. It happens in one of two ways: when the air cools enough, or when enough water vapor is added to the air.... ( +expand to view full text )

Description: Clouds are water. As you probably know, we can find water in three forms: liquid, solid and gas. Water as a gas is called water vapor. Clouds form when water vapor turns back into liquid water droplets. That is called condensation. It happens in one of two ways: when the air cools enough, or when enough water vapor is added to the air. You've seen the first process happen on a summer day as drops of water gather on the outside of a glass of ice tea. That's because the cold glass cools the air near it, causing the water vapor in the air to condense into liquid. Unlike the drops on the side of your glass though, the droplets of water in a cloud are so small that it takes about one million of them to form a single raindrop. Most clouds form this way, but the cooling comes not from ice in a glass, but as the air rises and cools high in the sky. Each tiny cloud droplet is light enough to float in the air, just as a little cloud floats out from your breath on a cold day.