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