Hi Mary,
Good question! A substance's state can
normally be a solid, liquid, or gas, depending on its temperature and
pressure. (I'll talk only about pure water for the moment, and your
bottle of mineral water may indeed have less dissolved stuff in it than
some tap waters.)
The molecules in a gas are loosly arranged
and move freely, colliding with each other occasionally. The molecules
in a liquid are constantly interacting with their neighbors, but they
still have too much energy to settle down. The molecules in a solid are
locked in a rigid pattern in space and for most substances are closer
together on average in the solid than they are in the liquid. Water is
an exception to this -- it expands when it freezes at ordinary
pressure, which is why ice floats on the top of a frozen lake. And also
why you will break a glass bottle of mineral water if you put it in the
freezer.
So for most substances, (except water for now, I'll
get back to it!) you can get them to solidify at room temperature if
you squeeze on them hard enough, forcing the molecules to get close
together and arrange themselves in the rigid solid pattern. Water's the
peculiar one and it works backwards -- you can get ice to melt by
squeezing on it! See our answer to this question: .
So
you might think this one's hopeless. But have no fear, ordinary water
has even more surprises locked up inside of it,if you squeeze it
*really really really* hard. I'm getting this information from .
Room temperature is about 300 K, so squeezing the water to a pressure
of one billion Pascals -- about 10,000 atmospheres or the pressure
you'd get under 64 miles of water (if there were such a place), then
the water at room temperature will turn to ice, and your bottle will be
broken. The funny thing is that the ice won't be the usual ice we get
in our freezers, but one with a different ordering pattern for the
water molecules (the ordinary one takes up too much space).
So,
yes, you can do it, but it is really difficult. A more popular
demonstration sometimes done is a bit of a cheat on this question but
also illustrates some fun physics. If you pump all of the air out of
the bottle with a vacuum pump, then the water inside will start to
boil. It takes heat energy to release a water molecule from the liquid
to the gas, and so the whole thing cools down when this happens.
Eventually the remaining water will get cold enough to freeze, which is
very entertaining because it is done without the aid of a freezer. It
isn't quite the answer to your question, because the water gets very
cold in the process, and so this whole thing doesn't happen at room
temperature as asked. Also, the time I saw it done was with a small
amount of water in a very tiny dish -- it may be hard to get a bottle
of mineral water to work because heat may leak in through the sides
faster than it can be removed by the boiling.
Tom
(published on 10/22/2007)
