Entropy: Joules per Kelvin Explained

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    Entropy Principle
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SUMMARY

Entropy is quantitatively defined as the measure of the number of specific arrangements of a system, expressed in units of joules per kelvin (J/K). This unit reflects the relationship between energy and temperature, specifically the heat transferred into a system at absolute temperature (in Kelvin). The interpretation of entropy as "disorder" is misleading; instead, it is fundamentally linked to the second law of thermodynamics, which governs the behavior of energy and heat transfer in thermodynamic systems.

PREREQUISITES
  • Understanding of thermodynamic principles, particularly the second law of thermodynamics
  • Familiarity with the concept of absolute temperature in Kelvin
  • Basic knowledge of energy transfer and heat in physical systems
  • Awareness of the Boltzmann constant and its role in statistical mechanics
NEXT STEPS
  • Explore the implications of the second law of thermodynamics in various physical systems
  • Study the relationship between entropy and statistical mechanics using the Boltzmann constant
  • Investigate the concept of absolute temperature and its applications in thermodynamics
  • Review resources on the misconceptions surrounding entropy and disorder, including educational videos
USEFUL FOR

Students of physics, thermodynamics enthusiasts, and professionals in scientific fields seeking to deepen their understanding of entropy and its implications in energy systems.

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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