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 Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=5110