Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: What is the physical interpretation of enthalpy and entropy?

  1. Sep 1, 2007 #1
    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
     
  2. jcsd
  3. Sep 2, 2007 #2
    clasius equality means that net entropy of an isolated system increases.
     
  4. Sep 2, 2007 #3

    Pythagorean

    User Avatar
    Gold Member

    would you mind giving us your own attempts at answers to your questions?
     
  5. Sep 3, 2007 #4
    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!
     
  6. Sep 3, 2007 #5
    i have informayion on it!
    come and visit my blog and you will see half a page of it!
    Thermodynamics
    but im 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: Sep 3, 2007
  7. Sep 4, 2007 #6


    will go to see it after a few minutes.

    thanks.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook