Understanding Entropy and Equilibrium: Debunking the Confusion

AI Thread Summary
The discussion clarifies the confusion surrounding entropy and equilibrium, specifically addressing a textbook statement that suggests the entropy of the universe is both zero and at maximum at equilibrium. It explains that while the entropy of a system at equilibrium remains constant, it is at its maximum value because entropy generally tends to increase. The conversation suggests that the textbook may have misused terminology, implying that the change in entropy (dS) is zero for small changes in an equilibrium system, rather than stating that the entropy itself is zero. This distinction is crucial for understanding the concept of entropy in thermodynamics. Overall, the thread resolves the confusion by emphasizing the importance of precise language in discussing entropy and equilibrium.
jisun.hong
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I'm so confused.
So my textbook tells me that entropy of the universe is equal to zero at equilibrium.
And then later on it tells me at equilibrium the universe achieves maximum entropy.
So is it zero or max?
Thanks for the help.
 
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Maximum since entropy tends to increase. So if you have a system at equilibrium it means that its entropy remains constant, but as entropy tends to increase it means that the entropy of the system is at its maximum. It seems that your book take the whole universe as a system, so replace "system" by "universe" in my post and all is fine.
 
Could your book have said that the change in entropy (mathematically, dS rather than S) is zero for small changes to a system in equilibrium?
 
Mapes said:
Could your book have said that the change in entropy (mathematically, dS rather than S) is zero for small changes to a system in equilibrium?
Good catch Mapes :) Must be this.
 

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