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Name: Jasmine
Status: student
Age: 19
Location: N/A
Country: N/A
Date: 7/14/2004


Question:
When the solid and liquid phases are in equilibrium, which phase, solid or liquid contains the greater amount of energy?


Replies:
There is a quantity called "free energy" or "chemical potential" (different names, essentially the same things though). When two phases or even three phases (solid, liquid, vapor) are in equilibrium their "free energy" or "chemical potential" are equal. In fact that is the definition of phases being in equilibrium. Things get a bit tricky because you might say that to melt a solid, I have to "add" heat, so the liquid must have the higher energy. However, that energy "cost" is exactly balanced by an increase in the "entropy" (roughly the amount of disorder), so all of the energy you put into melting goes to creating the liquid, hence the temperature stays constant. Hang in there you asked a very good thoughtful question. It is just that the "answer" is not so transparent.

Vince Calder



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