Energy Balances with Phase Changes: Summary

The answers to the ConcepTests are given below and will open in a separate window. 
Key points from this module:
  • The concept of state function can be used to simplify energy balances with phase changes.
  • Phase changes (melting, evaporation, sublimation) have large changes in enthalpy.
  • Heat of fusion is the enthalpy change when solid melts (\(\Delta H > 0\)).
  • Heat of vaporization is the enthalpy change when liquid vaporizes (\(\Delta H > 0\)).
  • Sensible heat is the enthalpy change when temperature changes for single-phase systems (calculate using heat capacities).
  • Latent heat is the enthalpy change associated with a phase change at constant temperature and pressure.
  • For an ideal mixture, the sensible heat or latent heat changes can be calculated by treating each component independently.
From studying this module, you should now be able to:
  • Solve energy balances that involve phase changes.
  • Explain the differences between sensible heat and latent heat.
 
Prepared by John L. Falconer, Department of Chemical and Biological Engineering, University of Colorado Boulder