Back to Demo ListTo show the formation of clouds from adiabatic cooling and the importance of condensation nuclei.
Insert the rigid tubing into the stopper and connect the flexible tubing to the rigid tubing. Add enough water to cover the bottom of the jar and place the stopper on top. The water in the jar should be at room temperature for the demonstration. Clean the condensation off the sides of the jar by swirling the water to wet the sides.
Step A. Inflate the Jar with ~10 pumps and leave the pressure in the jar momentarily. Suddenly release the pressure, mimicking a rapid ascent, and observe a shocking lack of cloudiness, unless there are already enough particles in the jar (make sure the jar is clean to avoid this problem).
Step B. Attach a match to a long stick and light it. Once the match is burning well, blow it out and poke it down into the jar, hopefully filling the jar with some amount of smoke, don't worry, even a little smoke will make a good cloud. Repeat step A and a cloud should form.
You can dissipate and regenerate the cloud by pumping up the pressure and releasing it.
large glass jar (carboy) with enough water to cover the bottom
single hole stopper
~5 cm rigid tubing & ~10 cm flexible tubing
small hand pump
matches
The rapid decompression should mimic the decompression felt by ascending air parcels, which should produce a slight cooling in the jar. This cooling should facilitate cloud droplet growth, dependent upon the presence of enough CCN.
Clouds in a Glass of Beer - Simple Experiments in Atmospheric Physics by Craig G. Bohren, Wiley Science Editions, 1987.
Mark Roddy, Summer '88
edited by C. M. Bitz,
edited further by R. Eastman