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Make a cloud and learn about the Ideal Gas Law

by Tony Wayne and so many others. I think Steve Spangler was the first one I saw doing this.



Materials Picture

  • Air pump (I like the small air pump because student can easily see what is happening when it is placed on the table.)
  • Empty 2 liter bottle (You will not need the cap.)
  • Stopper that will fit on the bottle's opening
  • Needle for inflating a ball. (This one came with the pump.)
  • Drill with a 1/16 inch drill bit. (not pictured.)
  • safety glasses (not pictured)
  • water (not pictured)




Cork with a needle through itCarefully drill a hole in the top of the stopper. Be careful not to drill into yourself. The stopper is can be difficult to hold. I held it with a pair of pliers and placed it on a piece of wood.

Carefully push the needle into the hole you drilled. Push it all the way through.

Attach the needle cork combination to the air pump.


The demo


Put a 7 to 10 drops of alcohol into the bottle. Put about 7 to 10 drops of water also in the bottle. Rotate the bottle in your hands to spread the alcohol around for about 10 seconds. This will generate a lot of alcohol vapor in the bottle. That's what you want.
Put the cork in the top of the bottle.
Hold the cork down very firmly. Have someone else pump the air pump about 10 to 15 times. The cork will try to pop off. Hold it very tightly so it does not pop off and hit anybody in the face.
Quickly remove the cork from the bottle. (It will pop off on its own.) A cloud will form!
Repeat this process and the cloud will disappear while under pressure.


What's going on?


When the air is pumped into the bottle it is warmed by the pump. When the air is suddenly released, this quick expansion causes the air to cool very rapidly and water droplet condense on the alcohol.




Measure the temperature of the air in the bottle before and after the cork is removed.


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