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by evanb
2093 days ago
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Chemical bonds are on the scale of eV---the cost to liberate an electron from a hydrogen atom is 13.6eV, for example. So the best you can hope for, in a chemical reaction, is a change in mass of the scale of 10s of eV / c^2. In comparison, a single proton weighs 938 MeV = 9.38e+8 eV. So the fraction of the mass that is converted into energy is on the scale of 1e-7. |
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There's no such thing as conservation of mass, mass and energy are convertible into each other. But in the real of chemistry that conversion happens on a ratio of at most 1e-7, so when it comes to the human body we might as well say that the weight that goes in must equal what comes out, and that's close enough.