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· The diagram illustrates changes that occur during a first
order phase transition.
· From the expression for the
Gibbs function:
dg = -s dT + v dp , and the requirement that phases in equilibrium
have the same value of the Gibbs function it is seen that there are discontinuous
changes in the specific
entropy and specific
volume of the sample during the
phase transition.
· The change in specific entropy in a constant pressure
process is given by: s
= - (dg/dT)p
· The change in
specific volume in a constant temperature process is given by: v = (dg/dp)T
· The heat
of transformation associated with the
phase transition, lif
= T (sf - si ) , where the subscripts
indicate the initial (i) and final (f) states of the system. |
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