Saturday, March 12, 2011

Lucky Science: Cloud in a Bottle

March may come in "like a lion" but this is one cloud that won't dampen your spirits (or your clothes!)

Cloud in a Bottle

What you need:
  • One liter clear plastic bottle + cap
  • Foot pump with rubber stopper attached
  • Rubbing alcohol
  • Safety glasses
While wearing safety glasses, put just enough rubbing alcohol in the bottle to cover the bottom and swirl it around. Put the rubber stopper on. Pump the foot pump 5 times being sure to hold the stopper tight to the bottle. Then pull out the stopper and you will see a faint "poof" of a cloud. If it's very faint, that means there wasn't enough pressure. Repeat the experiment pumping 10 times this time, still holding the stopper tight to the bottle. This time the cloud should be more visible but you may wish to repeat again with 15-20 pumps, still holding the stopper tight to the bottle. Then after removing the stopper you should see a good cloud.

What's happening?

By pumping the bottle with pressure, you are forcing the water molecules to compress. When the pressure is released, the molecules expand and cool the air. The cooler air allows the molecules to condense and form tiny water droplets. 

You can watch Steve Spangler do the experiment and explain it on this video and you can read about the experiment here

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