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Clouds

This Science Minute was researched and written by Anne B., Ithaca, NY.

Do you know how clouds are formed? It's actually a simple combination of evaporation and condensation. But what does that mean?

Well, let's start with evaporation. Did you ever open a full bottle of water and forget to put the cap back on? You came back later and some of the water was gone! What happened? The liquid water evaporated into water vapor, a gas, and it rose into the air.

Condensation is the reverse process: it's when water vapor turns back into liquid drops. Sometimes when it's cold out, you see water on your window. That's condensation.

Now, let's put it all together to make a cloud. Water evaporates in the air, and the vapor travels up into the atmosphere. But higher up in the atmosphere, the temperature is colder. Then condensation kicks in. The water vapor cools, and if little particles of dust are around, the water droplets will condense on them, forming a cloud.