Entropy: Joules per Kelvin Explained

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    Entropy Principle
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Discussion Overview

The discussion centers around the units of entropy, specifically why entropy is expressed in joules per kelvin. Participants explore the relationship between energy, temperature, and the concept of disorder in thermodynamic systems, addressing both theoretical and conceptual aspects.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about the intuitive meaning of entropy's units, questioning how joules per kelvin relates to the disorder of a system.
  • Another participant suggests that entropy can be transformed into a dimensionless value using the Boltzmann constant, indicating that the units are a matter of unit conversion.
  • A participant points out that the "disorder" interpretation of entropy may be misleading and references a video for further explanation.
  • Some participants assert that the units of joules per kelvin follow from the second law of thermodynamics and explain that energy represents heat transferred into the system while temperature is the absolute temperature in Kelvin.
  • There is a clarification regarding whether the temperature refers to the absolute temperature before heat energy is transferred into the system.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the intuitive understanding of entropy's units, and multiple perspectives on the interpretation of entropy and its relationship to disorder remain present.

Contextual Notes

Limitations include potential misunderstandings of the disorder interpretation of entropy, as well as the dependence on definitions of energy and temperature in the context of entropy changes.

Saado
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Whilst I understand that entropy is a measure of the number of specific ways in which a system may be arranged. The units for entropy don't make sense to me intuitively. Why joules per kelvin? What way at all does that show how "disordered" a system is. When I hear joules per kelvin, I think of energy/average thermal energy.

What does the energy and temperature represent in this case?
 
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You can transform it to a dimensionless value with the Boltzmann constant. And that is just a unit conversion factor.
 
Saado said:
What way at all does that show how "disordered" a system is.
Here is a nice video on why the "disorder" interpretation of entropy is misleading:



More links in the video description on youtube.
 
Why joules per kelvin?
It follows from the second law of thermodynamics.
What does the energy and temperature represent in this case?
It is the change of entropy. In this case, energy is the heat transferred into the system and temperature is the absolute temperature (in Kelvin) the system at.
 
td21 said:
Why joules per kelvin?
It follows from the second law of thermodynamics.
What does the energy and temperature represent in this case?
It is the change of entropy. In this case, energy is the heat transferred into the system and temperature is the absolute temperature (in Kelvin) the system at.

So the temperature is the absolute temperature before the heat energy is transferred into the system?
 

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