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Difference between enthalphy and heat?

  1. Sep 27, 2005 #1
    in my thermodynamics textbook, enthalphy=U+PV
    and (delta)heat=(delta)U+(delta)PV
    those 2 look the same...
    can anybody explain the difference?
  2. jcsd
  3. Sep 27, 2005 #2


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    Hi asdf1. Take a look at your book again, I think you've taken it out of context. For example, flow through a pipe where heat is added or removed between two points in the pipe is a process in which the heat added/removed is equal to the enthalpy change in the fluid. On the other hand, for the situation where heat is added to a sealed container (ex: a pressurized tank), the amount of heat added or removed is equal to the change in the fluid's internal energy.
  4. Oct 2, 2005 #3


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    I was taught that enthalpy was a property of a substance. Heat is a transport phenomenon only (i.e. transfer of energy) and that there is no such property as heat.
  5. Oct 2, 2005 #4


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    at constant pressure with only expansion work the enthalpy of the substance does equal to the heat pertaining to the situation, that is [tex]q_p [/tex]
  6. Oct 3, 2005 #5
    thanks!!! :)
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