Familiar Talks on Science: World-Building and Life; Earth, Air and Water.Gray, Elisha
Science
Familiar Talks on Science: World-Building and Life; Earth, Air and Water.
Gray, Elisha
Science
When water is under pressure the freezing point is reduced several
degrees below 32 degrees Fahrenheit. This fact has been determined by
confining water in a close vessel and putting it under pressure and
subjecting it to a freezing mixture, and by this means determining the
freezing point under such conditions. By putting a bullet or something
of that nature into the water that is subjected to pressure one can tell
by shaking it when the freezing point is reached. If water is put under
pressure and cooled to a point below 32 degrees, and yet still remains
in the liquid state, it may be suddenly congealed by taking off the
pressure; this shows that the pressure helps to hold the molecules in
the position necessary for the liquid state, and prevents the
rearrangement of them that takes place at the moment of freezing. When
the water molecules are arranged for the liquid condition they may be
compared to a spring that is wound up and held in position by the heat
energy that is stored in the water. And when this energy is given up to
a certain degree the power that holds the spring wound up is suddenly
released, when it unwinds and occupies a larger space. There is a force
that we may call polar force, which is constantly tending to push the
molecules of water into an arrangement such as we see when
crystallization takes place--as it always does in the act of freezing.
These polar forces cannot act so long as the energy in the form of heat
is sufficient to hold the water in the fluid state. But the moment this
energy, which tends to hold it in the fluid state, falls below that
which tends to rearrange it into the crystalline form, it is overcome by
the superior power of the latter force, and we have the phenomenon of
solidified water.
A very interesting experiment may be performed with a block of ice by
anyone when the ice is near the melting point. If a wire is put around
the ice and a sufficient weight is suspended to it, the pressure of the
wire on the ice will gradually liquefy that portion immediately under
the wire, which allows it to sink into the ice slowly, and as this
process goes on the ice freezes together again behind the wire, so that
in time the wire will pass entirely through the block and leave it still
a solid block, as it was before the experiment began.
Public-domain text, read in full here on John Shaqi.
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