"Because E=MC^2 a very tiny, virtually unmeasurable amount of matter is converted into energy during any energy exchange."

Bzzzttt!

That only applies to NUCLEAR changes/reactions - NOT CHEMICAL ONES.

In chemical reactions, SOME of the energy that in contained in chemical bonds may be released as heat energy, or the reverse, some heat may be absorbed.... thus there are two types of chemical reactions: Exo- giving out and Endo- taking in - thermic reactions. No energy is converted to mass or vice versa in these!

This also applies to photosynthesis (plants) and also photovoltaic reactions. No energy is converted to mass or vice versa in these!