1. Clouds

2. Cool Condensation 
Clouds are water. We can find water in three forms: liquid, solid and gas. Water as a gas is called water vapor.

3. Clouds form when water vapor turns back into liquid water droplets
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.

4. Cool Condensation 
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.

6. Cool Condensation 
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 looses heat energy.

7. Cool Condensation 
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. 

8. Too Clean for Clouds? 
Our air has to be just a little bit dirty for clouds to form. That’s because water vapor needs a surface on which to condense. Fortunately, even the cleanest air has some microscopic particles of dust, smoke or salt for water droplets to cling to, so the air is rarely too clean for clouds to form. 

9. Cloud Classifications
Meteorologists name clouds by how high in the sky they form and by their appearance. Most clouds have two parts to their name.
first part: height
second part: appearance  

10. Cloud Classifications
Cloud name
Height
Cirro
High, wispy – so high they are made of ice crystals
Alto
Middle
No prefix
Low clouds   

11. Cloud Classifications
Name
What it means
Cumulus
Puffy like a cotton ball, usually means fair weather
Stratus
Layered, cover much of the sky
Nimbo/nimbus
rain

13. Name That Cloud! Click to see pictures of clouds.
Can you name each cloud type?
Click to see if your answer is correct.

15. Stratus Clouds These clouds look like blankets of gray.
long low clouds
These clouds look like blankets of gray.

17. Cirrus
high thin clouds
Cirrus clouds are too high and too thin to drop any rain or snow on us.

19. Cumulus
puffy clouds
Cumulus clouds may be low in the sky, but they can be tall enough to reach to the middle of the sky.

21. Stratus
Do you remember why they are stratus clouds?

23. Cumulus
This puffy cumulus cloud is dark, because it is so full of water.
It is a cumulonimbus cloud. Nimbus means “rain” in Latin.
Big dark clouds like this are seen in thunderstorms.

25. Cirrus
Do you remember why they are cirrus clouds ?

26. How did you do? Are you ready to go out and practice on real clouds?
Do you want to go back and practice some more?
Click on the cloud to play again.