# NORTHWEST WEATHER WATCH

## Experiment #3: The Great Disappearing Cloud Trick

You can fill out this Lab Sheet on the computer and send it to your teacher's email address by clicking on the submit button when you are finished. Or click on this version, print it out, and fill it in by hand.

Question: How does air pressure affect temperature and cloud formation?

Activity

In this experiment you will be making a cloud appear just as you did in experiment #2. But in this activity you will also be making the cloud disappear. In fact, you will learn how to make your cloud appear and disappear and then appear again with just a touch of your fingers...just by putting a little pressure on the air or by releasing that pressure.

Have you ever watched the weather forecast on TV? Do you remember hearing the terms high pressure and low pressure? What kind of weather do we usually have when we are in a high pressure zone? In a low pressure zone?

In your hypothesis you must decide what effect high pressure has on the temperature of the air and on cloud formation and then how low pressure affects these same weather components.

You will need
for each group:

• 1 clear plastic 2 liter bottle with cap
• 1 thin liquid crystal
• temperature strip
• water (a few drops)
• matches
• safety goggles
for each student:
• Journal Page (definitions)
• 1 Lab Sheet
Procedure

The recorder will record the group's observations below instead of on the Lab Sheet. (We'll use that later.)

1. Place the temperature strip inside the bottle so that you can read it and fasten it to the bottle with tape.
2. Screw the cap tightly on the bottle.
3. Read and record the temperature before you begin the experiment.

The temperature in the bottle before the experiment is ___________________.

4. Lay the bottle on its side and push as hard as you can on the surface of the bottle. After about 30 seconds of pushing on the bottle, have a group member read and record the temperature (while you are still putting pressure on the bottle).

The temperature in the bottle now is ________________.

5. Now release the bottle and observe the temperature strip for 30 seconds. What happens to the temperature?

The temperature in the bottle _______________.

In your group's own words explain what effect "squeezing" or putting pressure on the air had on the temperature of the air inside the bottle.

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

Do you think you created a high pressure zone or a low pressure zone when you squeezed the air in the bottle? ______________________________________________________________________________

And now it's time for us to put a cloud in the bottle. What 3 ingredients will we need to make a cloud?

1. __________________________________________________________________
2. __________________________________________________________________
3. __________________________________________________________________
If you could name all 3 ingredients, you're ready to create a cloud in your bottle and to make it disappear!

Get out your Lab Sheet ....It's time to do some magic! Your recorder will need to list the experiment steps on your group's Lab Sheet.

This Experiment better known as The Great Disappearing Cloud Trick

1. Open the bottle and pour in a few drops of water.
2. Roll the bottle around to wet the surface inside and let stand for several minutes.

3. Lay the bottle on its side and push down on it as before. Have a group member light a match, blow it out, and insert the smoking end into the bottle. Quickly release your pressure on the bottle and screw on the cap.
• What do you see?
4. Now apply and release pressure as you did earlier - observing temperature changes and any visible changes to the air in the bottle.
• Did you see a cloud form?
• Did you see it disappear?
5. Write your observations on the Lab Sheet.
6. Go to Hypothesis Revisited. Do you want to change your hypothesis or keep it the same? Why?
Class Discussion

Following the class discussion your group should reassemble and decide upon your concluding hypothesis. When you have finished, turn in Experiment Sheet #3 and your group's Lab Sheet and go back to your desk.

Seatwork

Take out your Lab Journal and write your own explanation of how high pressure and low pressure affect temperature and cloud formation.