What is the physical interpretation of enthelpy and entropy?

AI Thread Summary
The discussion focuses on the physical interpretations of enthalpy and entropy, with enthalpy representing the heat available for work and entropy indicating randomness in a system. Participants seek clarification on whether changes in total energy equal changes in enthalpy in open systems and whether all reversible processes are adiabatic. The Clausius inequality is mentioned, highlighting that the net entropy of an isolated system increases, but its practical implications remain unclear to some. Additionally, the relationship between heat, work, and energy in closed versus open systems is confirmed. Overall, the conversation emphasizes a need for deeper understanding of thermodynamic principles.
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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 differnt 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 differnt 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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