Entropy-Volume Changes in a Closed System: Examining Heat and Work Effects

In summary: I don't see a connection between temperature and volume.As for the relationship between thermodynamic entropy and information entropy, there is no direct equivalence. They are related in the sense that both involve measuring uncertainty or randomness, but they are not equivalent. Work is not equal to information entropy, as work is a form of energy transfer while information entropy is a measure of disorder or unpredictability. Power is not equal to information entropy either, as power is a measure of the rate of energy transfer.
  • #1
sirchasm
95
0
In a closed system (which has no constructible physical reality), heat and work are distinct.

There are two paths a closed system can take, to reach the same point.

But, do both paths result in the same changes to the entropy-volume?


this question got trashed in another 'syince forum' - does anyone have a pointer?
 
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  • #2
Does "reach the same point" mean "reach the same state" or "reach the same energy"? If the former, then the entropy per unit volume is changed identically; entropy and volume are state variables. If the latter, then not necessarily; adding 10 J, say, by heat will change the entropy per unit volume in a different way then adding the same amount by work.

EDIT: I should explain the difference between the two endpoints. If you're assuming the two systems are brought to the same final state, this implies that the temperatures, volumes, pressures, energies, entropies, etc. are equal. Both heat and work must be applied to both systems to satisfy this condition, but there is no requirement on the order. The final entropy and entropy per unit volume will be identical. If you're assuming the two systems are brought to the same energy only (by heating one and doing work on the other) and the pressures, volumes, etc. can be different, then the total entropy will be higher in the system that was heated.
 
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  • #3
OK, if you're considering the volume of the physical gas, then entropy (thermodynamic) is a state variable = 'total energy'.

Work is 'energy per unit of time', thermodynamic entropy is 'global energy over time'.
Any physical work is a derivative of energy content, measurable as pressure (a deformation of volume) and temperature (a derivative of volume in pressure units); then "volume" of the physical gas is a diffusion which is positive or negative, according to entropy content; work is a measure of energy flow, and temperature is a measure of energy flow rate.

What about dimensionless information entropy? Does it have a volume or pressure? The units are (0,1), so what does information entropy correspond to in a gs?
 
  • #4
sirchasm said:
Work is 'energy per unit of time', thermodynamic entropy is 'global energy over time'.
Any physical work is a derivative of energy content, measurable as pressure (a deformation of volume) and temperature (a derivative of volume in pressure units); then "volume" of the physical gas is a diffusion which is positive or negative, according to entropy content; work is a measure of energy flow, and temperature is a measure of energy flow rate.

Except for "work is a measure of energy flow," this is mostly incorrect. It looks like you're just stringing technical terms together. I don't know what you're talking about.

When you say "Any physical work is a derivative of energy content," for example, does this correspond to the common definitions of work, derivative, and energy, and if so, how?
 
  • #5
Except for your misunderstanding of "work is a derivative", what prompted you to claim "this is mostly incorrect"?

Why is it mostly incorrect? (I got 'work = measure of flow', correct, huh?)

P.S. I appreciate being corrected if I am in fact, incorrect. I don't see the point of being told "that's incorrect", and waiting around for an explanation when there isn't one.

But, I suppose I should also appreciate that someone has bothered to at least post a response of some kind.
Yo' gets what yo' can in de big worl'
 
  • #6
Yes, "work is a measure of energy flow," is a statement resembling consensus physics (more accurately, we would say that "work is energy in transit," because power, not work, is a measure of energy flow per unit time). A similarly worded statement can be found in textbooks. It's compatible with the definitions of work and energy, and the units match (work and energy are measured in joules).

"Any physical work is a derivative of energy content" doesn't make any sense to me. Saying that temperature is "a derivative of volume in pressure units" doesn't make any sense to me. Perhaps they're misinterpretations of something you read. But personal theories are not appropriate for this forum; that's why I asked whether you are using standard scientific definitions. Can you provide a reference for these statements?
 
  • #7
Ok, just to see if we're on the same page, or if the page really exists, can you explain the equivalence between thermodynamic entropy, and information entropy?
What does work equal, in informational terms? Or power?

Any physical work, is derived from (physical) energy, energy and entropy are related (with no entropy volume, there is no energy). Therefore work is derived from entropy, or more exactly, from changes in entropy volume.
Even though thermodynamic work doesn't 'change' thermodynamic entropy...?
 
  • #8
OK, got it. By "derivative" you didn't mean differentiation, you just meant that they're related. Makes sense.

And what about the reference for saying temperature is "a derivative of volume in pressure units"?
 

Related to Entropy-Volume Changes in a Closed System: Examining Heat and Work Effects

What is entropy and how does it relate to volume changes in a closed system?

Entropy is a measure of the disorder or randomness in a system. In a closed system, where no matter can enter or leave, entropy tends to increase over time. This means that the system becomes more disordered and the energy within it becomes more evenly distributed. Volume changes in a closed system can affect entropy by changing the available space for particles to move and increasing the potential for disorder.

What is the relationship between heat and work in a closed system?

Heat and work are both forms of energy transfer that can occur in a closed system. Heat is the transfer of thermal energy between objects at different temperatures, while work is the transfer of mechanical energy through the application of a force. In a closed system, the total amount of heat and work must be equal in order to maintain the system's energy balance.

How do heat and work affect entropy in a closed system?

Both heat and work can contribute to changes in entropy in a closed system. Heat transfer can increase the disorder of particles within the system, leading to an increase in entropy. On the other hand, work can decrease the disorder by organizing particles or compressing them into a smaller space, resulting in a decrease in entropy. Overall, the net effect of heat and work on entropy will depend on the specific conditions of the closed system.

What are some real-world applications of entropy-volume changes in closed systems?

Entropy-volume changes in closed systems have many practical applications in fields such as thermodynamics, chemistry, and engineering. Some examples include studying the expansion and compression of gases in car engines, analyzing the behavior of refrigerants in air conditioning systems, and predicting the stability of chemical reactions. Understanding these concepts is also crucial for developing efficient and sustainable energy systems.

How is the Second Law of Thermodynamics related to entropy-volume changes in closed systems?

The Second Law of Thermodynamics states that the total entropy of a closed system will always increase over time, or at best remain constant. It also states that no process can occur that results in a net decrease in entropy. This law is closely related to the concept of entropy-volume changes in closed systems, as it explains why energy tends to disperse and systems tend towards disorder over time. The Second Law also plays a crucial role in determining the direction and feasibility of chemical and physical processes.

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