Two Entropy scenarios on a system

In summary, the conversation discusses two thought experiments related to the concept of entropy. The first experiment involves expanding the volume of a system containing a fixed number of atoms, while the second experiment involves reducing the kinetic energy of all the atoms in the system. Both of these scenarios are deemed impossible according to the laws of physics, making the question about the increase of entropy in these scenarios meaningless. The conversation also touches on the concept of vacuum pressure and the relationship between the energy of particles and the measure of vacuum. However, these concepts are not fully understood or explained. Overall, the conversation highlights the importance of basing questions on established scientific principles rather than impossible scenarios.
  • #1
MatthewKM
11
3
TL;DR Summary
Entropy, Brownian motion, volume vs temperature thought experiment
Entropy question.

Take a finite number of identical atoms in a specific volume of space at a moment of time.

Run two thought experiments on this system

scenarios (both time independent)

1: expand the volume of space of the system instantaneously by a factor of 10. The fixed number of atoms in the system have not, in that instant, yet reduced (or increased) their individual kinetic energies but the vacuum pressure has reduced in the system concordant with the increase in volume.

2: Instantaneously reduce the kinetic energy of all the atoms in the system uniformly without changing the volume of the system such that the total heat in this system is equal to scenario #1 concordant with Avogadro’s law

Are either of these two impossible scenarios both unique descriptions of entropy increasing according to the second law of thermodynamics or is entropy an entanglement of these two scenarios?
 
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  • #2
MatthewKM said:
the vacuum pressure
What "vacuum pressure"? What are you talking about?

MatthewKM said:
Instantaneously reduce the kinetic energy of all the atoms in the system
This is, as you admit, impossible.

MatthewKM said:
Are either of these two impossible scenarios both unique descriptions of entropy increasing according to the second law of thermodynamics or is entropy an entanglement of these two scenarios?
None of the above. Asking about impossible scenarios is pointless; you can't ask the laws of physics to tell you what happens in a scenario that violates the laws of physics. That's nonsense.
 
  • #3
Yes impossible I totally agree. Vacuum pressure? with this impossible question part of the impossibility of the question is that the measure of vacuum is determined by the energy of the particles within so I was trying to address this in the question by referring to vacuum in that context. The thrust of the question is to try to parse entropy into two different effects or states. Uniformity of the distribution of particles and energy of those particles That's all. Of course I know it is an impossibility I said that at the outset. Didn't intend to make anyone angry
 
  • #4
MatthewKM said:
the measure of vacuum is determined by the energy of the particles within
I have no idea what you mean by this or where you are getting it from.

MatthewKM said:
The thrust of the question is to try to parse entropy into two different effects or states. Uniformity of the distribution of particles and energy of those particles
I have no idea where you are getting this from either. I think you need to find an actual reference (textbook or peer-reviewed paper) that discusses entropy and frame a question based on that instead of trying to make up impossible scenarios yourself.

MatthewKM said:
Of course I know it is an impossibility I said that at the outset.
And, as I said, it is pointless to discuss impossible scenarios since the laws of physics can't tell us anything about them.

MatthewKM said:
Didn't intend to make anyone angry
I don't know where you are getting the idea that anyone is angry. I am simply pointing out to you that the question you have posed is unanswerable as you posed it, and explaining why.
 
  • #5
The OP question is unanswerable since it postulates scenarios that are impossible according to the laws of physics.

Thread closed.
 

1. What is entropy and how does it affect a system?

Entropy is a measure of the disorder or randomness in a system. It affects a system by increasing over time, leading to a decrease in the system's ability to do work and a decrease in its overall energy.

2. What are the two different entropy scenarios that can occur in a system?

The two entropy scenarios are the isolated system and the open system. In an isolated system, there is no exchange of energy or matter with the surroundings, so the entropy remains constant or increases. In an open system, there is an exchange of energy and matter with the surroundings, leading to a decrease in entropy.

3. How does the second law of thermodynamics relate to entropy scenarios?

The second law of thermodynamics states that the total entropy of a closed system will always increase over time. This means that in an isolated system, the entropy will always increase, while in an open system, the entropy will decrease as energy and matter are exchanged with the surroundings.

4. Can entropy be reversed in a system?

No, entropy cannot be reversed in a system. The second law of thermodynamics states that the total entropy of a closed system will always increase or remain constant. While in an open system, the decrease in entropy is only temporary and will eventually reach a state of equilibrium where the entropy remains constant.

5. How can entropy be calculated in a system?

The change in entropy can be calculated using the equation ΔS = Qrev/T, where Qrev is the reversible heat transfer and T is the temperature in Kelvin. This equation can be used to calculate the entropy change in both isolated and open systems.

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