Ask A Scientist© Weather Archive

name         Kim
status     Educator
age          30s

Question -   What is a good junior high science experiment on the
topic of dewpoint?

Kim -

Have you tried the 2 liter bottle/cloud chamber experiement.  It is a good
example of condensation at the dew point, but you must first explain
adiabatic cooling... not too hard.

Raise the humidity in the bottle by adding a little water and sealing the
top.  Squeeze the bottle causing it to adiabaticly warm and therefore hold
more of the water in a vapor form.  Release the pressure on the bottle
causing the temperature to drop adiabaticly and ... Poof!...condensation.
The saturated air must give up some of its water because it has cooled to
the dew point.

Try it... you'll like it.

Larry Krengel
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