Weird Science: Smoke in a Bottle

HONOLULU (HawaiiNewsNow)-  Dr. V from Oceanit and Taizo are joined by a very smart, and brave little helper on Sunrise. It takes some work to show how pressure can cause smoke to appear out of thin air!

Dr. V Show:  Cloud-in-a-bottle

November 16, 2010

Things you need:

  • Empty 2-liter bottle
  • Rubbing alcohol
  • Bike pump
  • Rubber stopper

The experiment

Please do this and all experiments with adult supervision. Pour a little bit alcohol into your empty bottle. You want to get some particles in the bottle, so roll the bottle around to let the alcohol evaporate. Using the rubber stopper, have an adult have you create an attachment for your pump that will plug into the mouth of the bottle. Put the plug into the mouth of the bottle and give it ten good pumps. Then take the plug out quickly. What do you see? Try putting the plug back in and pump up the bottle again. What happens?

How does it work?

In your bottle you have water vapor, air and alcohol particles. When you pressurize the bottle by pumping air in, the air in the bottle squeezes together or compresses. When you release the plug, the pressure drops, letting the air expand. When that happens, the temperature of the air becomes colder. This cooling procedure allows the water molecules to stick together more easily, forming tiny water droplets, or in other words, a cloud. The alcohol particles help this to occur. Most water droplets are created when water vapor condenses around a condensation nucleus, a tiny particle of smoke, dust, ash, or salt. Clouds in the sky form when the unseen water vapor in the air condenses into visible water droplets or ice crystals.

Why do clouds sometimes form over the mountains?

What is fog? What is the weather like when it's foggy? Cold or warm?

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