What are the enthalpies of fusion, melting, vaporization, and condensation of water at the corresponding phase transition temperatures?

1 Answer
Truong-Son N.
Oct 10, 2017

Well, you can get some of them from Wikipedia, and then use knowledge of sign conventions to get the rest.

Wikipedia gives:

#DeltaH_"fus" = "6.01 kJ/mol"# at #0^@ "C"# and #"1 atm"#

#DeltaH_"vap" = "40.68 kJ/mol"# at #100^@ "C"# and #"1 atm"#

The enthalpy of fusion is defined for melting, since it is positive. Positive indicates absorption of thermal energy into the system, i.e. the ice, to melt it into water.

Therefore, #DeltaH_"frz" = -DeltaH_"fus" -= -DeltaH_"melt"#, for the process of extracting thermal energy from the system to freeze it.

The enthalpy of vaporization is defined for vaporizing, since it is positive. Positive indicates absorption of thermal energy into the system, i.e. the water, to turn it into gaseous water.

Therefore, #DeltaH_"cond" = -DeltaH_"vap"# for the process of extracting thermal energy from the system to condense it.

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