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Bottled Clouds

Illustrate the temperature drop of a sample of gas during adiabatic expansion. The temperature drop is manifested withthe formation of tiny water droplets suspended in the air inside the bottle. For this demo, we add some liquid water to a transparent jar and shake it well to saturate the air inside the jar (100\% relative humidity). We then increase the pressure in the bottle by some 20 psi. Finally, with a quick motion, we release the pressure from the bottle. The sudden release of pressure is important to insure that the expansion is close to being adiabatic. The temperature drop in the sample of saturated air should be enough to bring the sample to supersaturation. Supersaturated water vapor will condense over condensation nuclei and with enough condensation nuclei, there will be a large collection of tiny droplets to form a little cloud inside the jar. Normally there are plenty of condensation nuclei present in the air. However, to make the demonstration more dramatic, you could add some nuclei of your own (a smoking burned-down match or a few drops of rubbing alcohol are fine). The cloud can be visualized better by scattering some light from a lamp (or flashlight).
ID: d0010
Set up time:
5 to 10 minutes in class.
Requires:
water Components.
Notes:
You may need assistance the first time you use this demo.Add enough liquid water to cover the bottom of the jar with 2 to 3 cm of water- use a funnel to minimize spills.Shaking the water is important to get enough water vapor in the jar -keep the jar closed. While pressurizing the jar, you may need to keep your hand on the stopper. Don't forget to dim the lights in the room. You may want to show the experiment without the extra nuclei first.The choice between alcohol and matches is yours, but it seems thatmatches work best.
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Table of Components

Qty. name location notes
1 Transparent glass jar W106; South Wooden Shelves U1-L1 (by sink)
1 One-hole rubber stopper (Jar's plug) on Jar
1 Hose on Jar
1 Bicycle pump W106; South Metal Shelves; U2-L0 Optional, some people find it easier to just blow directly into the hose.
1 Funnel W106; South Wooden Shelves; U1-L1 (by Jar) optional to pour water into jar.
Optional, but matches are recommended