X-Message-Number: 5110
From: Brian Wowk <>
Date: Sun, 5 Nov 1995 11:48:29 -0600
Subject: SCI.CRYONICS Heat of fusion

	Bob Ettinger claims that applying pressure to a block of ice
at its freezing point will suddenly cause the entire block to melt
because of the freezing point reduction caused by the pressure.  Bob
speculates that the heat of fusion required for the melting comes
from the work done by the pressure, because (paraphrasing) "in an
adiabatic process the only possible source of energy is work."
This is not true.  A cursory calculation shows that at ordinary
pressures the PdV associated with melting is grossly inadequate
to provide the heat required for the phase change.

	When you apply pressure to an ice block at its freezing
point, *some* melting will indeed occur.  However most of the
energy for this melting does not come from work; it comes at the
expense of the temperature of the system (i.e. the temperature
drops).  When you do Bob's proposed adiabatic experiment, ice
will only melt until the decreasing temperature reaches the
depressed freezing point, at which time the whole process stops.

---Brian Wowk


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