Where is the chemical energy from?

I remember this big deal in high school chemestry about the discrepencies in mass between two molecules of hydrogen and one of helium, and how this missing mass was converted to energy according to the e=mc2 that we all have grown to love.

My question is: does this mass-to-energy thing happen in chemical reactions? We’re dealing with the electro-magnetic force now instead of the strong (??) nuclear force, but I can’t shake the feeling that somebody told me this once. I’m hoping that someone at the SDMB can straighten this whole issue out for me…

Short answer:No.

That would be “cold fusion”. Which has never been proven.

Short answer: Yes. (Sorry, Beeblebrox.)

As Beeblebrox points out, cold fusion doesn’t work, but the energy of chemical reactions does come from mass changes. Those changes are just very much smaller than the ones from nuclear reactions, and are mostly fairly easy to reverse.

Maybe I’m wrong,but I always thought that in a chemical reaction no mass was lost,just sort of moved around. Essentially… it takes energy to put some molecules together, so if you take them apart that energy is given back. I always believed in conservation of mass for non-nuclear reactions.

There is no such thing as "conversion, the mass change is the consequence of energy release, not the cause. When you have an exothermic reaction, some of the energy which was stored in the system is released as kinetic energy. After being transferred to the surrounding material, the original system is left with less energy, hence less mass. And it is just as true about chemical reactions as about nuclear ones.

The only difference is quantitative, not qualitative. The typical relative mass change in a chemical reaction is of the order of 10[sup]-9[/sup] - 10[sup]-10[/sup] , to small to be directly observable. The typical relative mass change in nuclear reactions is of the order of 10[sup]-3[/sup], which is quite easily observable. Why the difference? Not because there is different physics in action, just because the fields involved in nuclear binding are much stronger, thus the changes in binding energies are also proportionally stronger.

Yeah, what Ring said.

It’s misleading to think of conversion between energy and mass. Einstein told us that that the two are equivalent. If you have a sealed box and you poured some energy into it, it will get heavier by the amount predicted by e=mc^2. Without opening the box you can’t tell if the energy is stored as energy (say, by charging a battery, or compressing a spring) or by converting it into matter. In fact, such a distinction is impossible.

Jeez, if you are going to bring Shroedingers’s cat into this, at least do a better job of explaining it.

Mirage, the short answer is still no.

Forget the quantum mechanics and just think in terms of Newton and Einstein.

Beeblebrox, what scr4 said about energy and matter has nothing to do with Schrödinger’s cat or quantum mechanics, and I doubt he/she meant it to. The short answer is still yes and all you need is Einstein in order to say it. Cecil says:

I concur.

Damn, all that tuition spent on physical chemistry classes and I still apparently don’t know jack.

Please allow me the dignity to slink away quietly.

(shuffle, shuffle, shuffle)