What is heat?

[J.C.MacSwell]

 

 

Also, in regard to my lunch. It went from a state of relative disorder as a sandwich to a state of considerably greater complexity as part of my blood and bones, muscles, general cellular structure, mitochondria, ribosomes, lysosomes, enzymes, DNA etc. so how did the entropy or state of disorder of the sandwich increase ?

 

Greater complexity or not, the energy represented by your sandwich was at lower entropy earlier than later.

 

Complexity and order are both analogous and related to entropy but they are not the same thing.

[DrRocket]

 

What I am really interested in in regard to all this is how it might apply to a particular design for a Heat Engine of my own invention.

 

I've been told repeatedly by various persons over the years that it cannot work because it would be a violation of the Second Law of Thermodynamics.

 

 

aha

[J.C.MacSwell]

 

The definitions of "System", "open system", "isolated system" don't seem to have any governing rules. It is impossible to win an argument against the second law of thermodynamics not because it is true but because the game is fixed. Heads I win, Tails you lose. This kind of moving boundary argument is something I've seen repeatedly in discussions of the topic practically from its first inception. It seems to me that this is changing the definitions to satisfy what amounts to a belief, I think.

 

 

If you're starting to think Thermodynamics is an unfair game you are in very good company.

 

http://en.wikiquote.org/wiki/Thermodynamics

 

I find this very interesting. In particular

 

"Further, the energy that fuels you ultimately comes from the sun, so you don't have a closed system."

 

What I am really interested in in regard to all this is how it might apply to a particular design for a Heat Engine of my own invention.

 

I've been told repeatedly by various persons over the years that it cannot work because it would be a violation of the Second Law of Thermodynamics.

 

One of my arguments to the contrary was that the engine is not a closed system and that the fuel to run the engine is ultimately heat from the sun.

 

This seems to be the same as the argument you are putting forth here that Life does not violate the Second Law of Thermodynamics for the same reasons

 

I came to find out recently that Tesla conceived a similar engine that he believed could operate on ambient heat he called a "Self acting engine" - able to run on indirect heat from the sun stored in the medium.

 

He seems to be saying that it would be possible under some special circumstances which he describes quite clearly IMO, to extract heat from the atmosphere (heat ultimately coming from the sun) and convert that heat into a different form of energy so as to leave behind a "Sink" or "Cold Hole" for additional heat energy to flow into and thus be able to extract additional energy from that heat. The energy gained could then be used to expel any residual heat not converted so that the "cold hole" could be maintained indefinitely - so long as at least some of the incoming heat continued to be converted to some other form of energy.

 

It seems to me that my engine design is conceptually identical to what Tesla describes.

 

My question is, regardless of any particular design, conceptually, is Tesla's (or my) idea "a violation of the second law of thermodynamics" ?

 

I posted excerpts from Tesla's article here:

 

http://www.scienceforums.net/topic/46143-stirling-turbine/page__view__findpost__p__619315

 

There are also some diagrams and a GIF animation providing a conceptual "working model" of the engine.

 

I'm sure some posting here have already viewed this, but I would be interested in getting any opinions regarding this 2nd Law question.

 

You can use ambient temperatures to drive a heat engine as long as you have a sufficient heat sink. No violation of thermodynamics, and in fact they are theoretically more efficient than the equivalent heat source.

 

Unfortunately, you need an indefinite "re-source" to keep it going indefinitely. The same rules apply. Without a heat sink the ambient energies are useless, as are the heat source energies without the ambient. Useful energy diminishes in every case.

 

Even ideal reversible processes don't happen in reality. We just try to get as close as we practically can. At every point entropy is increasing so there is no point in tricking yourself into thinking you have beaten the system.

 

It's like a version of an Escher Waterfall: http://www.escapeintolife.com/wp-content/uploads/2010/08/Escher_Waterfall.jpg

 

In reality it doesn't happen. You can't point to even one point in time in the system where entropy is decreasing so there is no point in pondering the illusion of the whole thing.

Edited August 24, 2011 by J.C.MacSwell

[Tom Booth]

Greater complexity or not, the energy represented by your sandwich was at lower entropy earlier than later.

 

Complexity and order are both analogous and related to entropy but they are not the same thing.

 

But how can you really gauge complexity / order ?

 

I used to have this problem with my X-Girlfriend. I had some manuscripts I'd be working on and would have the chapters all organized so I could look everything over at a glance - spread out on a long table. Very complicated but well organized, slips of paper inserted between pages with notes, cross references, footnotes etc.

 

Whenever I went out though my girlfriend, in the process of straightening up the house would get things neat and organized by picking up my mess on the table and putting it all into a box in the back of the closet.

[finiter]

Now, as for their internal energies, well that would depend on their specific heat. So, the question now is, if we are using isothermal conditions, and we want to check to see of the internal energies are the same, then we simply must take the two containers of let's say 1g of an identical gas in each.. which container will experience an increase in temperature faster, or will the increase in temperature be the same?

For argument sake, I would say that it is the specific heat part that provides the information about temperature ( I am suggesting that there is heat energy which depends on specific heat and temperature). Temperatures above 0K indicate hot states; increase in internal energy causes heating, but temperature is not proportional to the increase in internal energy. The volume is a deciding factor; if it increases freely, temperature does not increase, if increase in volume is highly restricted, the temperature increases considerably.

In our case, to heat by one degree you have to compress both the containers. The work to be done for this will not be equal; the smaller container requires more work. However, according to my version, the work done does not impart any energy to the containers. It is a self limiting process; to heat it by another one degree the work done will be more than that.

The reply to the remaining parts will follow.

 

In the example of the two containers the temperatures were equal and so were the number of particles — they have the same energy. By definition. In fact, that was a given condition in the problem.

That was an arbitrary condition, and your explanation regarding it was logical and I agree that based on existing concepts your explanations are correct. This is just another possibility put forth to spin1/2, as a response to his question.

[spin-1/2-nuclei]

For argument sake, I would say that it is the specific heat part that provides the information about temperature ( I am suggesting that there is heat energy which depends on specific heat and temperature). Temperatures above 0K indicate hot states; increase in internal energy causes heating, but temperature is not proportional to the increase in internal energy. The volume is a deciding factor; if it increases freely, temperature does not increase, if increase in volume is highly restricted, the temperature increases considerably.

In our case, to heat by one degree you have to compress both the containers. The work to be done for this will not be equal; the smaller container requires more work. However, according to my version, the work done does not impart any energy to the containers. It is a self limiting process; to heat it by another one degree the work done will be more than that.

 

Hi Finter,

 

you've confused the conditions. I stated that we are in isothermal conditions for the one container that has been compressed, as you wanted in your first question. This was to hold the temperatures between the two containers constant at constant mass. You can reverse the roles of the container but either way you will need an external heating or cooling source on one of them to hold the temps constant with constant mass. If you simply start compressing one of the containers more, you cannot answer you question about the total energy.

 

The internal energy has two parts.

Kinetic and potential - you have mistakenly stated that these two energies are the same. They are not.

 

The kinetic energy is directly proportional to the temperature, but the internal energy is not. To understand the difference you need to look at the chemical potential. I have outlined how to do this in the previous post.

 

Thus to answer your question.. are the energies the same for the two containers under the conditions that you described, or when you compress one even more and hold that container or the other uncompressed container at constant mass and temp via isothermal conditions...

 

Well, if the temps are the same the kinetic energy is the same, but that says nothing about the internal energy since it is not proportional to the temperature and can be better explained by the specific heat.. Thus, to answer that question for yourself you will have to go through the exercise I gave you before. Your current association between specific heat and temperature will not answer your question.

Swansont thought you were talking about the kinetic energies, I assure you he is not suggesting that the internal energy is also proportional to the temperature.

 

this is from his own link:

"Temperature is not directly proportional to internal energy since temperature measures only the kinetic energy part of the internal energy, so two objects with the same temperature do not in general have the same internal energy (see water-metal example). Temperatures are measured in one of the three standard temperature scales (Celsius, Kelvin, and Fahrenheit)." - http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/temper.html

 

So,

back to the thought experiment to help you prove this to yourself...

 

If an equal amount of reactant is added to the two containers, which one will react faster? Why? What does that say about the internal energy (the chemical potential) of each container. Their temperatures and mass are the same due to isothermal conditions, but their pressures are not the same.

 

*note the hints I gave you in the previous post as well as the mathematical relationships and the chemical potentials direct relationship to concentration.

 

Cheers.

Edited August 24, 2011 by spin-1/2-nuclei

[finiter]

Q. In the case of your two containers the temperatures are the same, but the pressures are not. Thus if the conditions in the two containers are kept as described in your question and a reactive substrate is added to the gasses, the reaction of one container will go faster, but the question is, why and can this increase in rate be attributed to a higher internal energy - with respect to chemical potential - in one container over the other?

It is very difficult to answer this straight forward question. My earlier question (where does the energy come from?) is relevant here also. In my view, during chemical reactions internal energies of atoms are not released, but there is only a realignment of the external energies. It is just like this: the two gases when mixed align themselves as molecules, and the heat part and the rest have a different ratio. If the heat part increases, the temperature increases, and this shows that the product requires only less energy to remain at the original temperature. The extra energy can be siphoned out.

My earlier proposal that force cannot impart energy cannot be taken in isolation; it is indeed a part of a package.

 

The internal energy has two parts.

Kinetic and potential - you have mistakenly stated that these two energies are the same. They are not.

I am suggesting (maybe it is wrong) that instead of dividing the internal energy as kinetic and potential, you may divide it as heat part and the rest. In that case, if you say the temperature is 100K, then you know that it has more internal energy than it would possess if it were at 90K, the rest of the conditions being the same. If you know the specific heat, you can have an approximate idea of heat part. The temperature is not at all an indicator of internal energy. For a different gas, the same internal energy will give you a different temperature. That is, internal energy is something that we do not measure.

[spin-1/2-nuclei]

It is very difficult to answer this straight forward question.

 

Okay, well let's walk through it and see if we can get to an answer...

I will give you some other hints...

 

1. "Chemical energy is the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances. Breaking or making of chemical bonds involves energy, which may be either absorbed or evolved from a chemical system. Energy that can be released (or absorbed) because of a reaction between a set of chemical substances is equal to the difference between the energy content of the products and the reactants. This change in energy is called the change in internal energy of a chemical reaction." - http://en.wikipedia.org/wiki/Chemical_thermodynamics#Chemical_energy

 

2. "Molecules undergo many characteristic internal vibrations. Potential energy stored in these internal degrees of freedom contributes to a sample’s energy content, [9] [10] but not to its temperature. More internal degrees of freedom tend to increase a substance's specific heat capacity, so long as temperatures are high enough to overcome quantum effects." - http://en.wikipedia.org/wiki/Heat_capacity#Extensive_and_intensive_quantities

 

3. "The heat capacity of most systems is not a constant. Rather, it depends on the state variables of the thermodynamic system under study. In particular it is dependent on temperature itself, as well as on the pressure and the volume of the system." - http://en.wikipedia.org/wiki/Heat_capacity#Extensive_and_intensive_quantities

Remember specific heat describes the substance, and specific heat describes the entire system.

 

Remember:

Increasing pressure on reactions that involves gasses will in crease the reaction rate. If you increase the pressure on solids or liquids it will have no effect on reaction rate.

 

Also remember that,

Chemical potential increase in areas of higher concentration and decreases in areas of lower concentration.

 

That is to say:

 

"Based upon this finding, we can conclude that the tendency μ of substances to change is not

only dependent upon the types of those substances, but also upon their amounts n: The greater

the amount of a substance (or the mass proportional to it) in the reaction chamber, the higher

its expected potential μ should be. Closer scrutiny of this effect which is known as mass ac-

tion shows that, in this case, the quantity n itself is unimportant. It is n in relation to the vol-

ume V in which a substance is distributed, meaning its concentration c = n/V, that is impor-

tant. If B or C, or both, participate as pure substances in a reaction, meaning at fixed concen-

trations, their amounts nB and nC have no influence upon the state of equilibrium and there-

fore, upon the amounts of BD and CD formed. How much or how little of a substance is pre-

sent in this case, is apparently not decisive but rather how densely or loosely it is distributed

in the space. This means that the more cumu-

lative and concentrated the application, the

more intense the effect. In other words, the

mass of a substance is not decisive for mass

action, but its “massing”, its “density“ in a

space: not the amount, but the concentration.

Cato Maximilian GULDBERG and Peter

WAAGE of Norway brought our attention to this in the year 1864.

 

Thus, the chemical potential of substances and the tendency to change increases according to

how strongly concentrated they are. Conversely, the chemical potential goes down when the

concentration of a substance decreases. We will use an example from everyday life to illus-

trate this. According to the values of the chemical potentials, pure water vapour must con-

dense at room conditions:" - http://docs.google.com/viewer?a=v&q=cache:4JHbuxVJWzgJ:www.job-stiftung.de/pdf/skripte/Physical_Chemistry/chapter_5.pdf%3FhashID%3D46fr9mvrkqcdaf0d1m9jdq0o90+chemical+potential+increases+with+concentration&hl=en&gl=za&pid=bl&srcid=ADGEESgn7cmu8rryQ0p1j1N71uXWQG7l3JIoFTCWK7rQ1ibhoSt1dOVBuiqWsbnQ72a61LFVv1tx259uYxmj1x2BbeTuU1k-BwoaDr3_Kcm-CKIF7WUGycbvzZ2l7llOastjpi5LI-G9&sig=AHIEtbQRsM4qshFH-HxI3FZArz6ef_lUNQ

 

Please read the link above because it will better explain all of this not only mathematically but semantically as well.

 

You can look at chemical potential like gravitational potential to see why it is not always the same in different concentrations - "the gravitational potential at a location is equal to the work (energy transferred) per unit mass that is done by the force of gravity as an object moves to that location from a reference location. It is analogous to the electric potential with mass playing the role of charge. By convention, the gravitational potential is defined as zero infinitely far away from any mass. As a result it is negative elsewhere." - http://en.wikipedia.org/wiki/Gravitational_potential

 

"Potential Energy

An object can store energy as the result of its position. For example, the heavy ball of a demolition machine is storing energy when it is held at an elevated position. This stored energy of position is referred to as potential energy. Similarly, a drawn bow is able to store energy as the result of its position. When assuming its usual position (i.e., when not drawn), there is no energy stored in the bow. Yet when its position is altered from its usual equilibrium position, the bow is able to store energy by virtue of its position. This stored energy of position is referred to as potential energy. Potential energy is the stored energy of position possessed by an object." - http://www.physicsclassroom.com/class/energy/u5l1b.cfm

 

That is to say, though you've kept the mass and the temperature the same in each container, since their pressures are different, are the molecular configurations different or are they the same, what does the information about chemical potential and concentration provided in this post suggest?

 

Hope this helps..

Cheers

 

*note molecular configuration in this sense means position of molecules relative to each other. Not bond configuration.

Edited August 24, 2011 by spin-1/2-nuclei

[Tom Booth]

You can use ambient temperatures to drive a heat engine as long as you have a sufficient heat sink. No violation of thermodynamics, and in fact they are theoretically more efficient than the equivalent heat source.(...)

 

...You can't point to even one point in time in the system where entropy is decreasing so there is no point in pondering the illusion of the whole thing.

 

As far as the heat engine is concerned, I could really care less about entropy & the second law. I just want to know if there is any chance in Hades of the thing actually working.

 

If the second law doesn't apply because it is not a closed system then I can stop worrying about finding loopholes in the second law.

Edited August 24, 2011 by Tom Booth

[J.C.MacSwell]

As far as the heat engine is concerned, I could really care less about entropy & the second law. I just want to know if there is any chance in Hades of the thing actually working.

 

If the second law doesn't apply because it is not a closed system then I can stop worrying about finding loopholes in the second law.

 

Tesla's idea won't work. He was hoping for a perpetual motion machine.

[Tom Booth]

Tesla's idea won't work. He was hoping for a perpetual motion machine.

 

Maybe,

 

I'm not entirely sure. It seems like a gray area.

 

Some things can look like, or in being described, sound like perpetual motion but aren't.

 

The difference between one and the other can be rather subtle sometimes, especially if only going by a description.

 

For example, If I say that I'm going to use a siphon to extract energy. I'm going to take the siphon and put it in some water and then put a turbine in the siphon tube and in this way get "free energy" indefinitely without having to do any additional work.

 

Is that "perpetual motion" or isn't it ?

 

Sounds like it and it could be, but maybe not.

 

I didn't say that I was going to use the energy produced by the turbine to pump the water back to its source to start the process all over again making it a closed system. Also I didn't mention that by "some water" I meant a lake at a high elevation in an area of adequate rainfall to keep the lake filled.

 

The difference is one is an open system the other isn't. I don't think Tesla was proposing a closed system.

 

You can put Tesla's proposed engine in a sealed room and say "see, if you put it in a closed room it would be perpetual motion". But that is taking an open system and changing the conditions to make it a closed system and is not what Tesla proposed at all.

 

But, I'm guessing you are right anyway. Probably couldn't work, but I still see it as a gray area.

 

As far as I know, nobody has ever tried it, although in some respects I think the principle has already been demonstrated on a small scale, though even this is debatable I suppose.

 

For example, there is no stable "heat sink" for the heat engine (in the following video) to run on. If this heat engine were to stop running for some reason the "Heat Sink" in the form of effective evaporative cooling would disappear. The cooling or "Heat Sink" is created "on the fly" through the engines own mechanical output.

 

The engine uses its own power to maintain its own cooling system and so run on a combination of ambient heat and evaporative cooling but it is not "perpetual motion" because it is an open system. It is, in effect, a very small and inefficient ambient heat engine. Theoretically you could build a giant version of this thing and set it next to a lake and it would run and perhaps generate power "indefinitely".

 

 

 

Looks like perpetual motion but isn't. But again, I'm afraid this is getting off topic here, even if it is "heat" related.

[J.C.MacSwell]

Maybe,

 

I'm not entirely sure. It seems like a gray area.

 

Some things can look like, or in being described, sound like perpetual motion but aren't.

 

The difference between one and the other can be rather subtle sometimes, especially if only going by a description.

 

For example, If I say that I'm going to use a siphon to extract energy. I'm going to take the siphon and put it in some water and then put a turbine in the siphon tube and in this way get "free energy" indefinitely without having to do any additional work.

 

Is that "perpetual motion" or isn't it ?

 

Sounds like it and it could be, but maybe not.

 

I didn't say that I was going to use the energy produced by the turbine to pump the water back to its source to start the process all over again making it a closed system. Also I didn't mention that by "some water" I meant a lake at a high elevation in an area of adequate rainfall to keep the lake filled.

 

The difference is one is an open system the other isn't. I don't think Tesla was proposing a closed system.

 

You can put Tesla's proposed engine in a sealed room and say "see, if you put it in a closed room it would be perpetual motion". But that is taking an open system and changing the conditions to make it a closed system and is not what Tesla proposed at all.

 

But, I'm guessing you are right anyway. Probably couldn't work, but I still see it as a gray area.

 

As far as I know, nobody has ever tried it, although in some respects I think the principle has already been demonstrated on a small scale, though even this is debatable I suppose.

 

For example, there is no stable "heat sink" for the heat engine (in the following video) to run on. If this heat engine were to stop running for some reason the "Heat Sink" in the form of effective evaporative cooling would disappear. The cooling or "Heat Sink" is created "on the fly" through the engines own mechanical output.

 

The engine uses its own power to maintain its own cooling system and so run on a combination of ambient heat and evaporative cooling but it is not "perpetual motion" because it is an open system. It is, in effect, a very small and inefficient ambient heat engine. Theoretically you could build a giant version of this thing and set it next to a lake and it would run and perhaps generate power "indefinitely".

 

 

 

Looks like perpetual motion but isn't. But again, I'm afraid this is getting off topic here, even if it is "heat" related.

 

Although it is a little vague, I'm basing my opinion on this line where I believe you were quoting Tesla:

 

"We would thus produce, by expending initially a certain amount of work to create a sink for the heat or, respectively, the water to flow in, a condition enabling us to get any amount of energy without further effort"

[Tom Booth]

Although it is a little vague, I'm basing my opinion on this line where I believe you were quoting Tesla:

 

"We would thus produce, by expending initially a certain amount of work to create a sink for the heat or, respectively, the water to flow in, a condition enabling us to get any amount of energy without further effort"

 

Yes, that is Tesla describing his theory. But this is IMO at least, identical to saying; (if we applied it to the "drinking bird"): "by expending initially a certain amount of work to create a sink for the heat... to flow in" (He is only using water as a metaphore for heat i.e. If we first dunk the drinking birds head into the glass of water to create a heat sink for ambient heat to flow towards) "We would thus produce... a condition enabling us to get any amount of energy without further effort" (i.e. the bird will continue drinking so as to maintain the sink while also producing some energy).

 

I realize Tesla was being, perhaps, a bit over-optimistic and envisioned something more than a toy bird generating a micro-amp but what he is suggesting IMO is no different in principle than the toy bird which does function as Tesla described. Once set in motion by getting its head wet and initiating a "heat sink" it keeps going on its own without any further effort on our part. Tesla was describing a heat engine and this bird is a heat engine that functions in the way he described, except perhaps in regard to the amount of useable energy produced.

 

Could this principle be scaled up to produce some usable energy for practical purposes ?

 

I'm not going to conclude its "impossible".

 

At least not until somebody actually tries it.

 

If the principle is sound, there are other more efficient ways of creating a "cold hole" than wetting 1/2 sqare inch or so of felt on a toy birds beak and much more efficient heat engines I should think.

Edited August 25, 2011 by Tom Booth

[finiter]

That is to say, though you've kept the mass and the temperature the same in each container, since their pressures are different, are the molecular configurations different or are they the same, what does the information about chemical potential and concentration provided in this post suggest?

So starting from the beginning: What I proposed was that the larger container can have a higher internal energy, though the temperature and the amount of matter is the same. The temperature neither represents the heat capacity nor the internal energy. The temperature does not represent the internal kinetic energy as well. The temperature is an indicator of the intensity of its potential state. The heat capacity can be regarded as the potential energy; however, the same heat capacity can create different intensities in different atoms. During reactions, internal energies of atoms are not released.

 

 

Now, the answer to your questions: The molecular configurations ( I mean the vibratory modes only) will be different because the heat capacities and the internal energies are different, but the ratio between heat capacity and internal energy can be the same (being at the same temperature).

 

Now let us bring two similar containers containing the reactant, which we assume to be gaseous. The internal energy of the two larger containers, one containing the reactant and the other containing the original gas that we have, will be different though they are at the same temperatures. Assuming that the two containers are interconnected and the reaction proceeds fully, the only thing left behind will be the product, which we again assume to be a gas. For this, the internal energy of the product should be less than the reactants at any given temperature. Naturally, after reaction, the product in the interconnected containers will be at a higher temperature. The same will be the case with the smaller container also. The only difference will be the heat capacities of the product at two different temperatures. The heat capacity being higher in the smaller one, the heating effect will be less in it and so the reaction will be faster.

 

 

[J.C.MacSwell]

Yes, that is Tesla describing his theory. But this is IMO at least, identical to saying; (if we applied it to the "drinking bird"): "by expending initially a certain amount of work to create a sink for the heat... to flow in" (He is only using water as a metaphore for heat i.e. If we first dunk the drinking birds head into the glass of water to create a heat sink for ambient heat to flow towards) "We would thus produce... a condition enabling us to get any amount of energy without further effort" (i.e. the bird will continue drinking so as to maintain the sink while also producing some energy).

 

I realize Tesla was being, perhaps, a bit over-optimistic and envisioned something more than a toy bird generating a micro-amp but what he is suggesting IMO is no different in principle than the toy bird which does function as Tesla described. Once set in motion by getting its head wet and initiating a "heat sink" it keeps going on its own without any further effort on our part. Tesla was describing a heat engine and this bird is a heat engine that functions in the way he described, except perhaps in regard to the amount of useable energy produced.

 

Could this principle be scaled up to produce some usable energy for practical purposes ?

 

I'm not going to conclude its "impossible".

 

At least not until somebody actually tries it.

 

If the principle is sound, there are other more efficient ways of creating a "cold hole" than wetting 1/2 sqare inch or so of felt on a toy birds beak and much more efficient heat engines I should think.

 

Nature can in fact maintain a "cold hole". Usually we expend less at the start by taking advantage of topography, but we do build dams and harvest hydroelectricity. Very inefficient when you look at the whole process, but the energy is "free" and being wasted otherwise.

 

So if that was what Tesla was thinking the principle is sound...and of course in accordance with the laws of thermodynamics.

 

A heat engine of sufficient size could produce power from the Sun, even somewhat indirectly using diurnal heating and nocturnal cooling or barometric pressure fluctuations.

 

The trick is concentrating what is "free" in a way that you can do it economically.

[spin-1/2-nuclei]

So starting from the beginning: What I proposed was that the larger container can have a higher internal energy, though the temperature and the amount of matter is the same. The temperature neither represents the heat capacity nor the internal energy. The temperature does not represent the internal kinetic energy as well. The temperature is an indicator of the intensity of its potential state. The heat capacity can be regarded as the potential energy; however, the same heat capacity can create different intensities in different atoms. During reactions, internal energies of atoms are not released.

 

 

Now, the answer to your questions: The molecular configurations ( I mean the vibratory modes only) will be different because the heat capacities and the internal energies are different, but the ratio between heat capacity and internal energy can be the same (being at the same temperature).

 

Now let us bring two similar containers containing the reactant, which we assume to be gaseous. The internal energy of the two larger containers, one containing the reactant and the other containing the original gas that we have, will be different though they are at the same temperatures. Assuming that the two containers are interconnected and the reaction proceeds fully, the only thing left behind will be the product, which we again assume to be a gas. For this, the internal energy of the product should be less than the reactants at any given temperature. Naturally, after reaction, the product in the interconnected containers will be at a higher temperature. The same will be the case with the smaller container also. The only difference will be the heat capacities of the product at two different temperatures. The heat capacity being higher in the smaller one, the heating effect will be less in it and so the reaction will be faster.

 

Hello Finiter,

 

In this case it is the concentration that controls the rate of the reaction, and the concentrations are different because the pressures are different. This is because mass and concentration are not the same thing although they are related.

 

Another thing to note, is that since internal energy is both kinetic energy and potential energy, and potential energy can be looked at like chemical potential (which can be compared to gravitational potential) in this case we cannot describe the total internal energy only by the kinetic energy of the system.. That is to say - the temperatures and masses of the two systems being held constant under isothermal conditions doesn't really tell us much about the kinetic energy.

 

Hopefully this was helpful,

Cheers..

[spin-1/2-nuclei]

@Finiter

 

*note above I meant to say the temperature doesn't tell us much about the internal energy...

sorry if that caused any confusion.. working long hours here - and I don't always have time to proof read my posts.. sorry..

Cheers.

[J.C.MacSwell]

@Finiter

 

*note above I meant to say the temperature doesn't tell us much about the internal energy...

sorry if that caused any confusion.. working long hours here - and I don't always have time to proof read my posts.. sorry..

Cheers.

 

At equilibrium, assuming one phase, and knowing the gas, liquid or solid involved, doesn't the temperature tell you a lot about the internal energy in most cases?

 

Even if they are directly linked to kinetic energies, are they not measurably linked to the others?

[spin-1/2-nuclei]

At equilibrium, assuming one phase, and knowing the gas, liquid or solid involved, doesn't the temperature tell you a lot about the internal energy in most cases?

 

Even if they are directly linked to kinetic energies, are they not measurably linked to the others?

 

No - not necessarily - see the links I provided in the posts I gave before. The temperature is only directly proportional to the kinetic energy. The internal energy is comprised of both kinetic energy and potential energy. So in this case one container relative to another - one of them under isothermal conditions to keep both containers at constant temp (they are at constant mass), the pressure produces a different concentration of the gas - and therefore a different chemical potential.. Thus in this case both containers are at equilibrium, yet they do not have the same internal energy when an equal amount of reactant is introduced into both containers because their chemical potential is different despite the fact that their temperatures, and masses are the same. So the same kinetic energy but different internal energy..

 

So, you can relate the chemical potential with temperature mathematically (lagrange multiplier for average particle constraint in a system during maximization of entropy), but this does not mean that the temperature describes the internal energy of the system (even at equilibrium).. it does not.. temperature is directly proportional to kinetic energy not the internal energy..

In the Gibbs free energy equation.. deltaG=deltaH-TdeltaS temperature is related to the change in the entropy of the system..

 

To better understand this situation, you can look at chemical potential like gravitational potential.. If I have two 100kg balls and place one of them at the top of the hill and another one of them on a completely flat surface they will have different potential energies. Since in molecules the internal energy includes chemical potential the configuration of the molecule must be taken into consideration.. both the position of the molecules relative to other molecules as well as the literal molecular configuration. This changes with environment.

 

That is to say that not all equilibrium conditions for one set of reactants will produce the same internal energies for said reactants if/when they are placed in conditions to react with another substance..

 

Some reactions have multiple reaction pathways - as in they can undergo many different mechanisms - which will produce different transition states of different energies, and depending on what conditions you hold constant at the previous equilibrium prior to the reaction beginning - i.e. - depending on where you hold the equilibrium values at, you can in fact get very different products with different stability. Since chemical potential describes how likely a chemical transformation, phase change, or configurational change is to take place, talking about internal energy while excluding the chemical potential is a lot like talking about the total energy of a 100kg ball absent of it's position - i.e. - in exclusion of it's location..

 

hopefully this was helpful..

Cheers..

[finiter]

... the temperature doesn't tell us much about the internal energy...

That is, the larger container can have a higher internal energy than the smaller container having the same amount of gas (both being at the same temperature), and hence my suggestion that compression does not impart energy, but only causes some changes in the system, may be a correct interpretation.

[spin-1/2-nuclei]

That is, the larger container can have a higher internal energy than the smaller container having the same amount of gas (both being at the same temperature), and hence my suggestion that compression does not impart energy, but only causes some changes in the system, may be a correct interpretation.

 

Hello Finiter,

 

not if you're suggesting that the increase in temperature - which is a result of the increase in kinetic energy - doesn't come from the work done on the system during compression. The act of compressing does do work on the system and hence increases the kinetic energy, which in turn increases the temperature...

 

Since internal has many other parts, not just kinetic energy - it is impossible to tell the total internal energy of a system from the increase kinetic energy alone. Yet, if there is an increase in temperature there MUST be an increase in kinetic energy, however the same is not true for the internal energy.

 

One can say that if there was an increase in the specific heat - i.e. how long it will take to increase the temperature of 1kg of the substance in the system by 1k or in the case of heat capacity the entire system, one can then say that there may have been a change in internal energy (but even this will not quantify an exact relationship between the internal energy and the increase or decrease in time it takes to warm a system or cool it.

 

Now, that doesn't mean that temperature and internal energy are not related but rather that they are not directly proportional and thus you cannot get the kind of information that you want about the internal energy from the temperature.

 

Hope this was helpful,

Cheers..

Edited August 26, 2011 by spin-1/2-nuclei

[finiter]

Now, that doesn't mean that temperature and internal energy are not related but rather that they are not directly proportional and thus you cannot get the kind of information that you want about the internal energy from the temperature.

Your explanation is very clear: ie, though the larger container can have higher internal energy, that cannot fully account for the heat removed after compression, and so, some energy has to be put into it; this comes from the work done.

My argument is only that the force applied cannot on its own impart energy, some other source has to be identified. However, in this case, the internal energy cannot be the source. In the case of mechanical compression, it may be possible to point out other sources.

Anyway, calling the heat capacity of the system as the 'heat energy' of the system, I think, is logical.

[swansont]

Your explanation is very clear: ie, though the larger container can have higher internal energy, that cannot fully account for the heat removed after compression, and so, some energy has to be put into it; this comes from the work done.

My argument is only that the force applied cannot on its own impart energy, some other source has to be identified. However, in this case, the internal energy cannot be the source. In the case of mechanical compression, it may be possible to point out other sources.

Anyway, calling the heat capacity of the system as the 'heat energy' of the system, I think, is logical.

 

No, not according to the definitions already in place.

[finiter]

No, not according to the definitions already in place.

Maybe. But it does not go against observational evidence. Without tampering with the observational evidence, we can always try out the possibility of an alternate explanation. I used the word logical only to that extent.

Edited August 28, 2011 by finiter

[swansont]

Maybe. But it does not go against observational evidence. Without tampering with the observational evidence, we can always try out the possibility of an alternate explanation. I used the word logical only to that extent.

Using the definitions, it does go against observational evidence. A force acting through a distance does work, and that adds or subtracts from the energy present. That is what observational evidence shows. You have to come up with new terminology and a new self-consistent model.