What is the physical interpretation of enthelpy and entropy?

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Homework Help Overview

The discussion revolves around thermodynamics, specifically focusing on the physical interpretations of enthalpy and entropy, as well as their implications in different types of systems. The original poster poses several questions regarding the relationships and definitions within these concepts.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster seeks clarification on the physical meanings of enthalpy and entropy, questioning the implications of changes in these quantities. They also inquire about the relationship between total energy and enthalpy in open systems, the nature of reversible processes, and the significance of the Clausius inequality. Some participants ask for the original poster's attempts at answering their own questions.

Discussion Status

Participants are actively engaging with the original poster's questions, with some providing partial insights while others express uncertainty. There is a mix of attempts to clarify concepts and requests for further elaboration on the original poster's understanding.

Contextual Notes

The original poster's questions suggest a need for foundational understanding of thermodynamic principles, and there is an indication of varying levels of familiarity with the subject among participants. Some responses reference external resources, though their relevance remains uncertain.

mune
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Hi guys, I need help on thermodynamics:

1. what is the physical interpretation of enthalpy and entropy?

2. in an open system, change in total energy = change in enthalpy?

3. every reversible process must be adiabatic?

4. what does clausius inequality means?

5. Q-W=U is for closed system? and Q-W= enthalpy + KE + PE is for steady state open system?

thanks
 
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clasius equality means that net entropy of an isolated system increases.
 
would you mind giving us your own attempts at answers to your questions?
 
1. what is the physical interpretation of enthalpy and entropy?
enthalpy, U+PV, is the heat can be used to do work and entropy, dQ/T is a measure of randomness. but i still don't understand, what does a large change in enthalpy and a small change in enthalpy means physically? same for entropy.

2. in an open system, change in total energy = change in enthalpy?
this one i don't quite understand, i saw it in an example, wonder if it is always true.

3. every reversible process must be adiabatic?
because reversible process does not leave trace to environment, so i guess dQ=0, which is adiabatic. But I am not too sure about it.

4. what does clausius inequality means?
sum of Q/T of a cyclic process is zero, if it is reversible, and less than zero, if it is irreversible. but i don't know what is the use of this inequality, what does it implies? if it measures entropy, then why do we need to know change in entropy?

5. Q-W=U is for closed system? and Q-W= enthalpy + KE + PE is for steady state open system?
this one i knew the answer. yes and yes.

pls tell me if you know anyone of the answers. Thanks!
 
i have informayion on it!
come and visit my blog and you will see half a page of it!
Thermodynamics
but I am not that sure if it will help
because i posted the info on different types of it.
ok , i'll try to help you research on the questions you asked.
 
Last edited:
kaisxuans said:
i have informayion on it!
come and visit my blog and you will see half a page of it!
Thermodynamics
but I am not that sure if it will help
because i posted the info on different types of it.
ok , i'll try to help you research on the questions you asked.



will go to see it after a few minutes.

thanks.
 

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