Why there isn't a work term in entropy balance equation?

[alpyurtsever]

Hi, I need your help in my homework. My Instructor asked that question? Why there is not a work term in entropy balance equation?

 

I have researched about it and I found that,

 

entropy has not an exact physical meaning, however it is associated with disorder or randomness. In another point of view, entropy defines the energy which is unable to do work.

however I am not sure that these definitions are enough.

 

On the other hand, I think entropy is a mathematical derivation, which is done by a purpose of having a balance equation which does not involve a work term.

They have originated it from the one directional flow of heat (from high temperature to low). Is it true?

 

Thanks for your help

[Rhiaden]

The thermodynamic meaning of entropy is a irreversible thermodynamic process.

 

The simplest way to look at what your instructor has asked you is to consider what you are looking at with entropy. When calculating the change in entropy for a system, you are looking only at the initial and final state of a system

 

When you talk about work in a thermodynamic balance equation, what are you describing in regard to the state changes?

 

This link might also help Thermodynamics Entropy wiki

 

Also try this one: Entropy & Thermodynamics

 

 

Sorry for the obscure answers, but I cannot think of how to explain it better without giving you the answer

 

Hopefully someone else will be able to do it in a simpler way than I have

Edited November 21, 2010 by Rhiaden

[cypress]

Hi, I need your help in my homework. My Instructor asked that question? Why there is not a work term in entropy balance equation?

 

You seem to have some basic idea of the answer but I tend to agree that you should take a step back to the fundamentals of thermodynamics as alpyurtsever implied.

 

I have researched about it and I found that,

 

entropy has not an exact physical meaning, however it is associated with disorder or randomness. In another point of view, entropy defines the energy which is unable to do work.

however I am not sure that these definitions are enough.

 

These definitions not enough as you suspected, and they are incomplete/inaccurate for this purpose because they don't adequately address the context of your instructor's question.

 

Entropy laws are exact, furthermore they are based on probability theory. The intent is to provide a model for how ordered systems behave when they are driven by random processes. Since interactions of molecular systems are governed by Brownian motion which is a random process, during these interactions the distribution and direction of heat energy flux is prescribed by the behaviors of random processes and the outcomes predicted by probability.

 

On the other hand, I think entropy is a mathematical derivation, which is done by a purpose of having a balance equation which does not involve a work term.

They have originated it from the one directional flow of heat (from high temperature to low). Is it true?

 

In a sense it is, so let's explore this further since it provides a hint at the question being posed. Heat and work are both measures of energy but think about the distinction between work processes and heat transfer processes in the context of randomness. Do you detect any distinction? If you can, do you see why it is not that work was purposefully left out but that work "falls" out due to this distinction?

 

You are correct that the second law, involving entropy, was originated in part to model the direction of flow of heat (or any ordered system under influence from random processes) apparently always in one direction at the macro level (when dealing with sufficiently large sets of particles such that probabilistic norms hold). Given that this is the purpose, have a look at the links offered, find the equation for the relationship between heat energy and entropy and use it to add additional context to the questions I posed in the previous paragraph. The answer lies within these considerations.

 

It is my hope that this will help you answer the question posed by your instructor.

[alpyurtsever]

I have allready looked at the links I am very happy now. Thank you for all your answers. I think I can answer the question with a good accuracy now. Moreover, I am happy about understanding what entropy is, because it is a difficult concept to understand, and that was a big step in this way I had allready have an idea about the relation between one direction flow, and now I am also getting into the context of randomness.