binding energy and rest energy
in [Physics]
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From: Michael Moroney on 1 Jun 2010 20:56 "I. F." <exformatist(a)gmail.com> writes: >hi, >are there other cases than the binding energy where the rest mass (of >electrons) is decreased or increased by absorbing or emitting photons? >in such case, the rest mass of electrons would not be invariant, am i >right? Any reaction that emits or absorbs net energy will cause a change in the measured mass of the result compared to the starting products. Two water molecules (H2O) have less mass than the sum of two hydrogen molecules (H2) and one oxygen molecule (O2) because some energy was also released. It's just that the mass difference in non-nuclear reactions is so small that it's essentially unmeasurable. That's because c^2 (in the E=mc^2 equation) is a very large number. You may have trouble "assigning" where the mass or mass difference comes from, but for something like the chemical reaction of hydrogen burning into water, it's the electrons that are rearranged so it seems logical to think of the energy/mass difference as coming from them. It's really from the electric field within the molecules. Never mind Mitch/Burt, paying attention to his blitherings will only confuse you.
From: BURT on 1 Jun 2010 21:21
On Jun 1, 5:56 pm, moro...(a)world.std.spaamtrap.com (Michael Moroney) wrote: > "I. F." <exformat...(a)gmail.com> writes: > >hi, > >are there other cases than the binding energy where the rest mass (of > >electrons) is decreased or increased by absorbing or emitting photons? > >in such case, the rest mass of electrons would not be invariant, am i > >right? > > Any reaction that emits or absorbs net energy will cause a change in the > measured mass of the result compared to the starting products. Two water > molecules (H2O) have less mass than the sum of two hydrogen molecules (H2) > and one oxygen molecule (O2) because some energy was also released. It's > just that the mass difference in non-nuclear reactions is so small that > it's essentially unmeasurable. That's because c^2 (in the E=mc^2 > equation) is a very large number. > > You may have trouble "assigning" where the mass or mass difference > comes from, but for something like the chemical reaction of hydrogen > burning into water, it's the electrons that are rearranged so it seems > logical to think of the energy/mass difference as coming from them. > It's really from the electric field within the molecules. > > Never mind Mitch/Burt, paying attention to his blitherings will only > confuse you. Bonded particles are bonded by their own energy. When unbonded the field energy goes back into the mass. Unbound particles are heavier than when bonded. Electrons and protons bond to their atomic shells by their electric energy. Neutrons bond to neutrons through their strong field energy. Mitch Raemsch |