Thermodynamics Entropy state function?

In summary: Stockzahn says that if you put your book back in your back you're decreasing the entropy of the system, after you take it out again, you increase it to S'. With work, you can decrease the entropy of a system.
  • #1
Rohan Patil
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Entropy of any system is state dependent. I just read about thermodynamics and I got this question. I first set my system which contained my classroom, the hallway connecting my physics teacher's cabin and the classroom. Then let the entropy of the system be S when I was going to the classroom in the hall way.(The system conatins me and my teacher in the cabin who is reading a book.) I went to the classroom and took out my book from some bag, scribbled something and put it back in the bag again. Then I just sat there and after sometime took out the book when my teacher came in. He started teaching and I started taking notes. Let the entropy be now S'.
Nowe let us take another case. I never put my book inside the bag again. My teacher came in the classroom and I started taking notes. So now we again have the same entropy S'.
This means that even if danced around like a fool and then sat back, there should not be any change in the final entropy. So this means that if I calculate the change in entropy between two states, then I cannot tell what happened in between. But things should occur in only one manner or things should change in the system. I am not able to understand where my mistake is. Please help me out on this one.
 
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  • #2
Rohan Patil said:
Nowe let us take another case. I never put my book inside the bag again. My teacher came in the classroom and I started taking notes. So now we again have the same entropy S'.

If you put your book back in your back you're decreasing the entropy of the system, after you take it out again, you increase it to S'. With work, you can decrease the entropy of a system.

Rohan Patil said:
This means that even if danced around like a fool and then sat back, there should not be any change in the final entropy.

While dancing around your body increased its temperature and you sweated, so you transferred (more) heat from your body to the air by convection and to the wall by radiation and water of your body is evaporated (so changed from liquid to gaseous state) and spread in the air. All effects which increase the entropy of the system.
 
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  • #3
I think what stockzahn is saying is that, for the various situations you described, the final entropy of your system is not the same. Maybe you think it is macroscopically, but microscopically (which is what really counts), no.

Chet
 
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1. What is thermodynamics entropy state function?

The thermodynamics entropy state function is a measure of the disorder or randomness of a system. It is a state function, which means it only depends on the current state of the system and is independent of how the system got to that state.

2. How is entropy related to the second law of thermodynamics?

The second law of thermodynamics states that the total entropy of a closed system will always increase over time. This means that the disorder or randomness of a system will always tend to increase. Entropy can also be thought of as a measure of the unusable energy in a system, as it increases with energy dispersal and decreases with energy concentration.

3. What factors affect the change in entropy?

The change in entropy of a system depends on the amount of energy transferred, the temperature of the system, and the reversibility of the process. Generally, processes that involve energy dispersal and irreversible changes will result in an increase in entropy.

4. How is entropy related to the concept of equilibrium?

At equilibrium, the entropy of a system is at its maximum. This means that the system is in a state of maximum disorder and there is no potential for further energy dispersal. Entropy also plays a crucial role in determining the direction of spontaneous processes, as they tend to move towards equilibrium where entropy is at its maximum.

5. How is thermodynamics entropy state function used in practical applications?

The thermodynamics entropy state function is used in various practical applications, such as in the design of heat engines and refrigeration systems. It is also important in the study of chemical reactions and the prediction of their spontaneity. Additionally, entropy is used in the field of information theory, where it is a measure of the uncertainty or randomness of a message.

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