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Name:   Kevin M.
Status:  student
Age:  15
Location: N/A
Country: N/A
Date: 2000


Question:
Why does temperature remain constant during a phase change?


Replies:
Kevin,

As an example, consider melting an ice cube: As heat is added to the cube, the energy serves to break water molecules from the ice latticework. Rather than to raise the temperature of the surrounding water, the heat is used to continue the melting process -- to continue breaking water molecules from the lattice. The temperature of the surrounding water cannot rise until the ice has completely melted. At that time, additional heat will raise the temperature of the melt-water.

The same is true for the reverse process. As water is cooled and allowed to freeze, energy is released from the bonds that are formed as water molecules become incorporated into the ice latticework. That released energy holds the temperature constant until all the liquid water has been frozen. Continued cooling thereafter will reduce the temperature if the ice cube.

Regards,
ProfHoff



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