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Ice and Water

  1. Oct 25, 2007 #1
    Can someone help me understand this:

    By salting the crushed ice, the beer got cold faster.

    Why?! I have recently studied some Enthalpy, so if anyone could give me an explanation to this using anything related to Enthalpy I'd be very grateful!
     
  2. jcsd
  3. Oct 25, 2007 #2

    jim mcnamara

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    You don't even need enthalpy IMO.

    In general, an object immersed in liquid water will exchange heat with the liquid faster than it will with ice cubes - because of insulating air spaces.

    Salt allows the ice to liquify at a "below freezing" temperature, getting rid of the insulating air spaces. Colligative property of NaCl -> lowering freezing point of water.
     
  4. Oct 25, 2007 #3
    For school I need to know and understand this using enthalpy and enthropy. :)

    Thanks for the answer. Let me go through it, look up some words in a dictionary and I'll be right back!

    EDIT: OK I read through your reponse. It makes sense but isn't there much more to it? For exampleI have no idea where enthropy and enthalpy comes into the picture.

    My friend (who is, unfortunately, offline now and wont be able to help anymore) talked about bonds between the atoms and molekyles.

    He said something about the increasing enthropy which causes the ion-dipole bonds to weaken, and that's why energy is taken from the beer, which then gets cold.

    He also, some way got the enthalpy for the reactants (2648 kj/mol) ....
     
    Last edited: Oct 25, 2007
  5. Oct 26, 2007 #4

    chemisttree

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    You should look both at the enthalpy of melting of ice and the enthalpy of crystallization of salt. Likewise, you should think about what is entropy and how does it change when ice melts. How does it change when both ice melts and salt dissolves?
     
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