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Unit 13: Thermodynamics Page 15
This matrix holds the water to completely liquid, we notice
molecules in a crystalline pattern bubbling.
and the solid water holds its shape.
What’s going on now? If we were
Now, let’s turn on the heat. The
able to see the molecules of water
heat is transferred from the stove
at this point we’d be quite amazed
to the frying pan to the ice cube.
at the fantastic scene before us.
(We’ll talk about heat transfer a bit
later.) At 212° F or 100° C water goes
from a liquid state to
As the ice cube absorbs the heat
a gaseous state. This
the molecules begin to vibrate
means that the loosey
faster (the temperature is
goosey bonds that
increasing).
connected the
When the molecules vibrate at a molecules before
certain speed (gain enough have been stretched
thermal energy) they stretch those as far as they go,
strong, stiff bonds enough that the can’t hold on any
bonds become more like rubber longer and “POW!”
bands or springs. they snap.
When the bonds loosen up, the Those water molecules no longer
water loosens up and becomes have any bonds and are free to
liquid. There are still bonds roam aimlessly around the room.
between the molecules, but they Gas molecules move at very quick
are a bit loose, allowing the speeds as they bounce, jiggle,
molecules to move and flow around crash and zip
each other. around any
container they are
The act of changing from a solid to
in. The act of
a liquid is called melting. The
changing from a
temperature at which a substance
liquid to a gas is called evaporation
changes from a solid to a liquid is
or boiling and the temperature at
called its melting point. For water,
which a substance changes from a
that point is 32° F or 0° C.
liquid to a gas is called its boiling
Now we will watch carefully as our point.
ice cube continues to melt (little is
I don’t know about you, but I think
more exciting than watching an ice
it’s getting a bit hot in here. Let’s
cube melt - golf maybe). A bit after
turn the heat down a bit and see
we see our ice cube go from solid
what happens. If our gaseous
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