If you extract energy from a system, you also extract mass.
Particles have more mass when they travel faster. Heat is just increased particle velocity, when the atoms slow down as they cool, they lose mass.
So if you put coal and oxygen in an insulated container that completely contained the combustion and the heat, the mass would remain the same, but if you let it cool, it would lose mass.
The Hiroshima bomb lost about a gram of mass, we are talking thousands of tons of coal to produce that much energy, and the mass loss would be about a gram.
Which is why it can't be measured.

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"We have always known that heedless self-interest was bad morals; we know now that it is bad economics"
FDR's second Inaugural Address

Well, the theory is in that energy has mass in whatever way it is stored. Then if you move the energy you move it's mass with it. But this is only significant if you move a very large amount of energy (eg breaking the bonds holding protons and neutrons together as in fission). When the atomic bonds are broken in chemical reactions the mass involved in the relatively small amount of energy moved is so small that the Heisenberg principle may not permit measurements. The apparent lack of radiation in a chemical reaction does not disprove the theory because of this immeasurability.

If we some day find a way to overcome the measurement limitations then we may well discover a entirely new exotic form of radiation or need to modify E=mc2 and the relativity theory behind it.

I get the idea from reading a range of material in which there seems to be much debate.

Edit: Another explanation I have seen is that the energy is the mass and mass is the energy. A thing called mass-energy (I think). Exactly what that means I'm not sure.

No.

The transition of energy from a chemical bond to heat does not result in a loss of mass. You're wrong.

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I didn't say that, I said if the reaction was in an insulated container, it would retain all it's mass, if the heat escaped, it would lose an extremely small amount of mass, as the atoms average velocity was reduced, they would lose a small amount of mass, to small to measure in a practical way.

__________________
“ The subjects of every state ought to contribute towards the support of the government, as nearly as possible, in proportion to their respective abilities; that is, in proportion to the revenue which they respectively enjoy under the protection of the state.”

Adam Smith , The Wealth of Nations 1776

"We have always known that heedless self-interest was bad morals; we know now that it is bad economics"
FDR's second Inaugural Address

in reference to the OP, this sounds like cold fusion to me, something that is simply too good to be true, because it's not.

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“ The subjects of every state ought to contribute towards the support of the government, as nearly as possible, in proportion to their respective abilities; that is, in proportion to the revenue which they respectively enjoy under the protection of the state.”

Adam Smith , The Wealth of Nations 1776

"We have always known that heedless self-interest was bad morals; we know now that it is bad economics"
FDR's second Inaugural Address

Only if that energy correlates to a speed close to the speed of light. It doesn't in normal chemical reactions.
True only if their speed is close to the speed of light.
True.
Only if the energy loss from cooling correlates to a speed approaching or at the speed of light. That energy doesn't.
True because of conservation of mass. This technique, a bomb calorimeter, is used to measure the inherent energy of systems.
Only if the energy lost during cooling correlates to a speed close to the speed of light. It doesn't.
While the Heisenberg uncertainty is certainly applicable to atoms, it only applies to knowing their position without knowing their momentum or the converse. The position and momentum cannot be known at the same time. A good analogy to this principle is a battleship hitting a pea. You can know the position of the pea, but once the battleship hits it, within the constraints of the standard deviation of measurements for each, the position of the pea is now unknown but one could approximate the momentum. Conversely, if a pea hits a battleship, within those same constraints, the momentum of the battleship is unknown but its position is.

Bottom line, the laws of thermodynamics and the current research therein, maintain that energy is conserved.

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According to which law ?

They only have more relativistic mass, not the mass used in E=mc². In that context it's inertia.

The mass-energy equivalence expressed through E=mc² is possible with all materials, including coal, yes. But because it is convertible doesn't mean it actually gets converted in every type of reaction.

If you're claiming mass loss for chemical reactions, pray tell, what mass gets converted ? One of the constitutuents of the reaction would require an isotope change. But you start out with C and O ions and end up with C and O ions. The nuclei of C and O are not affected by chemical reactions. You need fission for that. The nucleus has got to be broken up to allow for one of the constituents to be converted to energy in the form of gamma radiation or other.

In C + O2 => CO2 you start with 22 neutrons, 22 protons, 22 electrons and end up with the same number, quite evidently so because none of the reacting constituents changes atomically. There simply isn't anything around to get converted from mass to energy.

All the other forms of energy in the process are merely transformations to and fro kinetic energy, enthalphy, heat, and whatnot. But all those are merely transformations of one form of energy towards another, and by the 2nd law the sum total remains the same.

So, the question is : what mass do you claim gets converted in chemical reactions ?

Another voice of reason.

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I am an American. That's the way most of us put it, just matter of factly. They are plain words, those four: you could write them on your thumbnail, or sweep them clear across this bright autumn sky. But remember too, that they are more than just words. They are a way of life. So whenever you speak them; speak them firmly, speak them proudly, speak them gratefully. I am an American. ...a tradition

in physics, we learned something about conservation of energy. is this like what were discussing? I failed physics so forgive me.

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It's easy to fail physics, no need to feel bad .

I'm a chemist, not a physicist. But we do have to have a rudimentary knowledge of the basics of mechanics, both Newtonian and quantum, and thermodynamics.

Yes, it's all about conservation of energy; that's the fist law of thermodynamics Laws of thermodynamics - Wikipedia, the free encyclopedia. Every time one has made the claim that they can get more energy out of a system than they have put into it, they have either miscalculated or poorly defined the boundaries of their system.

Or, they've lied:

Too good to be true | Life | Guardian Unlimited

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I am an American. That's the way most of us put it, just matter of factly. They are plain words, those four: you could write them on your thumbnail, or sweep them clear across this bright autumn sky. But remember too, that they are more than just words. They are a way of life. So whenever you speak them; speak them firmly, speak them proudly, speak them gratefully. I am an American. ...a tradition

If there isnt any loss of mass then where does the heat energy come from? If there would be no mass loss that would mean there is another sort of energy in the substance which is extracted.

Is chemical energy really energy or does it indicate that its easy to lower to mass of a substance to produce energy?

experts needed!

In chemical reactions, you make and break bonds between atoms. Those bonds have energy. The energy comes from bonds breaking and/or making in a reaction.

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I am an American. That's the way most of us put it, just matter of factly. They are plain words, those four: you could write them on your thumbnail, or sweep them clear across this bright autumn sky. But remember too, that they are more than just words. They are a way of life. So whenever you speak them; speak them firmly, speak them proudly, speak them gratefully. I am an American. ...a tradition

The theory is that the mass is not converted to energy but that the energy takes it's own mass with it when it is moved out of the bonds.

This is the mass of the energy it's self. It is not the mass of the constituent parts that is removed but the mass of the converted binding energy itself.

Nothing gets converted from mass to energy. It is the mass of the energy that is moved.

Because the energy carries the mass defect with it conservation of mass and energy is not defied.

None. In fact you may ask the same question of a nuclear fission. The following example is lifted directly from wiki (I'd encourage better refs.)

The difference in the bound and unbound masses of the proton-neutron pair is explained as the mass of the binding energy. Now since the binding energies of atomic bonds is much lower the mass defect is many magnitudes lower (in theory )


Please note: if anything I have said here contradicts anything I have said in previous posts this merely reflects a development of my understanding of the subject as this discussion progresses.

The energy itself has mass.

This entire thread contains posts that use reason. Each poster has contributed his/her version of reason based on a limited understanding of the subject matter. As a result I have learnt some stuff - (it prompted me to read more and challenge my assumptions.)

This is the problem the perpetual motion machine inventors have - they fail to challenge their assumptions and end up believing they have what they don't. A failure of reason.