Expert: James J. Kovalcin - 10/8/2006

Question
Could you describe, in subatomic terms (nuclei and electrons), what happens in a combustion reaction? Please include where the mechanical energy (following the reaction) of the involved particles comes from.

Thank you. I am curious as to whether or not my conceptions of what happens here at the subatomic level are accurate.

Answer
Chemical energy exists in the form of the electrostatic bonds between protons and electrons. If the distance between a proton and electron is reduced potential energy will be converted into kinetic energy. In a combustion reaction the average distance between protons and electrons is reduced and in the process kinetic energy is released in the form of heat.
[If you are interested in the math, electrostatic potential energy is given by U = -k*q1*q2/r. As the distance r between protons and electrons is reduced the potential energy becomes more negative. As the potential energy decreases (becoming more negative) kinetic energy is released.]