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Old 09-03-2011, 01:30 PM   #21
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Originally Posted by ajdelange
The heat comes from bond energy which derives from a combination of coulombic and Van der Waals forces. There is no conversion of mass to energy in these reactions. ... but photons have no mass so no mass is anihilated there.
^This is wrong, for one. The "mass" that we measure is only a measure of the amount of energy in a substance. Mass-energy equivalence, if you will recall. Nuclear reactions are NOT the only way mass and energy can be converted into each other - indeed, mass is a FORM or a measure, or perhaps a property, of energy.

And while it is true that photons have no mass in the relativistic sense, they do have energy, and gravity acts upon them (which is why black holes are, well, black). A warm solution, the same way, is heavier than a cold one, because there is more for gravity to act on. This however trips into the area of general relativity, which I'm terrible at.

For further reading: http://en.wikipedia.org/wiki/Mass-energy_equivalence
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Old 09-03-2011, 03:17 PM   #22
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^This is wrong, for one. The "mass" that we measure is only a measure of the amount of energy in a substance. Mass-energy equivalence, if you will recall. Nuclear reactions are NOT the only way mass and energy can be converted into each other
I just can't think of one. Do you have an example?

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- indeed, mass is a FORM or a measure, or perhaps a property, of energy.

And while it is true that photons have no mass in the relativistic sense, they do have energy, and gravity acts upon them (which is why black holes are, well, black).
What does this have to do with the heat of a chemical reaction.

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A warm solution, the same way, is heavier than a cold one, because there is more for gravity to act on. This however trips into the area of general relativity, which I'm terrible at.
If the gravitational field is so intense the space time tensor shows curvature weird stuff happens but I'm still calling BS on this one. In my lab warming or cooling a solution does not change it's mass. Again, how is this relevant to the question of energy released/absorbed in a chemical reaction.



If you really believe that mass is being converted into energy when a chemical bond is formed broken and wish to convince someone of this then I think it is incumbent on you to state which mass is being converted. I've gone through all the particles (except the sub atomic ones) and shown that none of them lose mass. Perhaps you think gravitons exist (they may) and that they have mass which is anihilated.

E = m*c^2 means that when m converts to energy the amount of that energy is m*c^2. It does not mean that it does convert or that the 2 are interchangeable in any other sense any more than the second law says a chemical reaction will take place if its application indicates an increase in entropy.

Apparently you have been exposed to some of this at least at the Wikipedia level but clearly misinterpret much of it. Thermodynamics is a macroscopic science. It is not concerned with forces that are 20 orders of magnitude less than anything that can be measured in the laboratory. In fact thermodynamics is a science of measurement.

If you read up on the fist law you will see that it is a conservation of mass/energy law and that the rest mass energy of electrons and nuclei are considered in the balance. But as this does not change during a reaction it cancels (thermo is concerned with changes in state variables - not their absolute values) and the first law is written dU = dq +dw. This simplified form ignores rest mass energy, electric or gravitational potentials, the fact that the carboy may be on it's way to the floor (kinetic energy) and so on because these are not relevant to the questions as to whether a reaction is thermodynamically feasible or whether it is exo or endothermic.

I'm not your P-chem teacher. If you want to understand this stuff I would suggest a good physical chemistry text. At least you'll know the difference between the 0th, 1st, 2nd and 3rd laws when you are finished.
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Old 09-03-2011, 03:28 PM   #23
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Some of these posts are a bit rude and/or unnecessary. While I don't have the scientific background to fully answer the OP, I'm positive that detailed discussions of relativity, gravitational fields, and space/time are irrelevant in order to provide the OP an answer. Should you want to continue those arguments, please post in another thread or continue via private message.

ajdelange's first post in this thread appears to sum up the concepts involved very nicely without running off on tangents that may be remotely relevant but aren't exactly of interest to the OP. Let's get back to that sort of discussion, please.

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Old 09-03-2011, 03:30 PM   #24
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Let us use Wikipedia again.

http://en.wikipedia.org/wiki/Binding...y#Mass_deficit

Quote:
Since all forms of energy have mass, the question of where the missing mass of the binding energy goes, is of interest. The answer is that this mass is lost from a system which is not closed. It transforms to heat, light, higher energy states of the nucleus/atom or other forms of energy, but these types of energy also have mass, and it is necessary that they be removed from the system before its mass may decrease. The "mass deficit" from binding energy is therefore removed mass that corresponds with removed energy, according to Einstein's equation E = mc2.
Thank you and have a nice day.


Edited to add: Yuri: Right. Sorry.
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Old 09-03-2011, 03:40 PM   #25
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Again, not relevant, but I agree with Yuri.

And if I've been rude I also apologize.

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Old 09-16-2011, 01:44 AM   #26
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I'm glad I found this thread and it was recent because I was wondering the same thing as the op.

Obviously it would be used to supplement hydrometer measurements, but I think it would be convenient to track the progress of the fermentation just by tossing the carboy on a scale and not having to expose the beer.

Also team ajdelange.

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