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

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


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    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


    User Avatar
    Homework Helper

    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


    User Avatar
    Science Advisor
    Homework Helper

    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!!! :)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook