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: Enthalpy question

  1. Sep 19, 2006 #1
    I'm breaking my mind on the next question. Why does the enthalpy of water lowers when the temperature rises?

    I would say you input heat-energy, so the enthalpy rises. But this does not seem true...
  2. jcsd
  3. Sep 19, 2006 #2
    i would dare say you have gotten your information wrongly. Once you heat anything, given that no chemical reaction occurs enthalpy will surely increase.

    In case you need prove heres http://www.thermexcel.com/english/tables/eau_atm.htm" [Broken]
    Last edited by a moderator: May 2, 2017
  4. Sep 19, 2006 #3
    Maybe it was entropy?
  5. Sep 19, 2006 #4
    yeah, seems backwards.

    As it was explained to me in my undergrad thermo class, enthalpy is the amount of energy you'd have to use to recreate the substance, including the energy needed to evacuate the volume occupied by the substance.

    More volume (by heating) means that you're going to need to take into account a larger amount of energy to evacuate that volume.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook