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Unit 13: Thermodynamics Page 21
Activities, Experiments, Projects
Note: This section is an abbreviated overview of the experiments online.
wrapper into a sheet and find a
Experiment: Homemade
way fasten the wrapper so it sits
Thermostat
upright on an index card (we used
If you can remember thermostats the bubble gum itself as the
before they went ‘digital’, then you adhesive). Stick it in the freezer
may know about bi-metallic strips overnight and check it in the
– a piece of material made from of morning! Where can you place it to
two strips of different metals which flex the other direction?
expand at different rates as they
How does that work? A
are heated (usually steel and
bimetallic strip is a stack of two
copper). The result is that the flat
metals stuck together. The metal
strip bends one way if heated, and
with the higher expansion is on the
in the opposite direction if cooled.
outer side of the curve when the
1. Normally, it takes serious skill strip is heated and on the inner
and a red-hot torch to stick two side when cooled. The bi-metallic
different metals together, but strip was invented by the
here's a homemade version of eighteenth century clockmaker
this concept that your kids can John Harrison to compensate for
make using your freezer. Here temperature-induced changes his
what you do: clock springs.
2. Tape a gum wrapper (one side
Experiment: Fire-Water
must be metallic) so it stands
Balloon
upright on an index card. Place
a piece of tape on each side. If you've ever had a shot, you
know how cold your arm feels
3. Insert into the freezer for an
when the nurse swipes it with a
hour.
pad of alcohol. What happened
4. Open freezer – your gum
there? Well, alcohol is a liquid with
wrapper should be curled up!
a fairly low boiling point. In other
Since gum wrappers are paper on words, it goes from liquid to gas at
one side and foil on the other, you a fairly low temperature. The heat
can use one to make your own bi- from your body is more than
metallic strip. Flatten out the
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