Entropy: Joules per Kelvin Explained

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Entropy is defined as a measure of the number of ways a system can be arranged, but its units of joules per kelvin can be confusing. This unit reflects the relationship between energy transferred into a system and the absolute temperature of that system, as dictated by the second law of thermodynamics. The discussion highlights that energy represents the heat added, while temperature indicates the system's state in Kelvin. The interpretation of entropy as a measure of "disorder" is considered misleading by some, emphasizing the need for clarity in understanding its implications. Overall, the connection between energy, temperature, and entropy is crucial for comprehending thermodynamic processes.
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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