2. First you need to know some facts about air and water: 1. Water evaporates and is called water vapor which behaves like all other gases. 2. When any gas expands rapidly it cools; when compressed rapidly it heats up. 3. Cool air cant hold as much water vapor in it as warm air can. 4. In the center of any cloud droplet (a tiny drop of water too small to fall to the ground) there is a tiny piece of matter…dust, salt etc.. 5. When water vapor condenses to liquid it must have an object or surface to condense on.

3. A. Does dew form when air heats up or cools off? B. When you pump air into a tire does the valve stem get warm or cool…..what happens when you let air out rapidly out? C. Why does dew collect on the outside of a glass of ice? D. Why do clouds form primarily on the windward sides of mountains? Why is there more rain there also? E. Why is the air more moist on one side of a mountain than on the other side usually?

4. Cloud chamber Bulb for pumping air into the bottle. There is a check valve here that only allows air to go one way

5. First, pump air into the bottle raising the pressure. After a few seconds the temp of the air is the same as the room

6. Open the hose to the air will rush out and the pressure will suddenly drop inside

7. 1. Does the temp of the air suddenly drop? 2. Where is the SURFACE on which water vapor may condense inside the bottle… could this make a cloud?

8. Do you see any clouds?

10. Adding a little liquid water to the bottle will help…..why?

11. Adding the smoke from produced when blowing out a match will help. Why?

12. Lets try again….this time with lots of very tiny smoke particles in the bottle and a lot more water vapor in the bottle.

13. A cloud is born!!!

14. Now you can explain what causes the cloud to form….next is a movie showing the Making of a Cloud… Can you explain, now, what makes the cloud quickly go away?

15. Click on slide to start movie; here to stop

16. ocean mountain Garden GrovePalm Springs Warm moist air less pressure more pressurerain dry