Why do different types of change involve different amounts of energy?

Can you tell me which type of energy change involves the most energy? Phase, chemical or nuclear changes? The least? And, just exactly why is this so?
starbuck15@hotmail.com

In general, phase changes absorb or release the least energy and nuclear changes the most. The trend is the result of the different magnitudes for the attractions and repulsions involved in phase, chemical, and nuclear changes. More energy is required to overcome stronger forces- and more energy is released when stronger attractive "bonds" form.

Phase changes involve intermolecular forces. For example, vaporization of water involves snapping hydrogen bonds between water molecules.

Chemical changes involve chemical bonding forces. For example, atomization of water involves snapping two oxygen-hydrogen bonds. Since chemical bonds are much stronger than intermolecular forces, chemical changes require (or release) far more energy than phase changes.

Nuclear changes involve even stronger forces that bind the nucleus together, and so will usually require or release even more energy than chemical changes.

Author: Fred Senese senese@antoine.frostburg.edu

Copyright © 1997-2005 by Fred Senese
Comments & questions to fsenese@frostburg.edu
Last Revised 07/31/07.URL: http://antoine.frostburg.edu/chem/senese/101/thermo/faq/phase-chemical-nuclear-energy.shtml