Notices
Results 1 to 12 of 12

Thread: Where does freezing water get its kinetic energy from?

  1. #1 Where does freezing water get its kinetic energy from? 
    Forum Freshman Gen1GT's Avatar
    Join Date
    Nov 2009
    Posts
    72
    We all know water expands as it turns to ice. This expansion can be enough to break water storage vessels, like water bottles. If the energy is being taken away to freeze the water, where does the energy come from to break a bottle?


    Reply With Quote  
     

  2.  
     

  3. #2 Re: Where does freezing water get its kinetic energy from? 
    Moderator Moderator Janus's Avatar
    Join Date
    Jun 2007
    Posts
    2,077
    Quote Originally Posted by Gen1GT
    We all know water expands as it turns to ice. This expansion can be enough to break water storage vessels, like water bottles. If the energy is being taken away to freeze the water, where does the energy come from to break a bottle?
    The energy isn't being "taken away", it is "given up". That energy has to go somewhere, and that is the energy that breaks the vessel. This Energy is the Latent heat, and is 334,000 J/kg for water.

    This latent heat used to be used by farmers back when they stored vegetables in root cellars. They would place large barrels of water in the cellars with the vegetables. This way, the latent heat given up by the water as it froze protected the vegetables.


    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


    Edit/Delete Message
    Reply With Quote  
     

  4. #3  
    Forum Masters Degree thyristor's Avatar
    Join Date
    Feb 2008
    Location
    Sweden
    Posts
    542
    I don't want to complain, but isn't this a somewhat peculiar way to look at it?
    I would say that the water freezes when it has been in thermal contact with some body of a temperature below zero long enough to give off its latent heat - not in the reversed order.
    I also thought that the farmers placing barrels of water in their cellars, was because the large specific heat capacity of water would prevent great drops in temperature.
    373 13231-mbm-13231 373
    Reply With Quote  
     

  5. #4  
    Forum Ph.D.
    Join Date
    Jan 2009
    Posts
    951
    there is no "kinetic" energy that's 1/2MV^2.
    expansion of ice is due to the heagonal lattice structure occupying more volume than the liquid.
    Reply With Quote  
     

  6. #5  
    Forum Isotope Bunbury's Avatar
    Join Date
    Sep 2007
    Location
    Colorado
    Posts
    2,590
    Quote Originally Posted by thyristor
    I don't want to complain, but isn't this a somewhat peculiar way to look at it?
    I would say that the water freezes when it has been in thermal contact with some body of a temperature below zero long enough to give off its latent heat - not in the reversed order.
    I also thought that the farmers placing barrels of water in their cellars, was because the large specific heat capacity of water would prevent great drops in temperature.
    I believe Janus is correct. The latent heat is released as the water freezes and this would help maintain a constant air temperature at 0degC until all the water is frozen. After that the heat capacity of the solid ice would probably help to slow the temperature drop.

    The corresponding reverse effect that's more intuitive would be evaporation of sweat from the skin. The latent heat of vaporization cools the skin.
    Reply With Quote  
     

  7. #6 Re: Where does freezing water get its kinetic energy from? 
    Geo
    Geo is offline
    Forum Junior
    Join Date
    Nov 2009
    Location
    New Zealand
    Posts
    273
    Quote Originally Posted by Gen1GT
    We all know water expands as it turns to ice. This expansion can be enough to break water storage vessels, like water bottles. If the energy is being taken away to freeze the water, where does the energy come from to break a bottle?
    When water freezes it's temperature remains constant. Because the temperature is not changing- this energy goes into forming hydrogen bonds which are intermolecular bonds. Bond forming releases heat.

    Because the temperature is constant - energy is going into forming bonds which cause the expansion.
    Reply With Quote  
     

  8. #7  
    Forum Freshman Gen1GT's Avatar
    Join Date
    Nov 2009
    Posts
    72
    Great answers. You have to admit, it's an odd effect.
    Reply With Quote  
     

  9. #8  
    Forum Masters Degree thyristor's Avatar
    Join Date
    Feb 2008
    Location
    Sweden
    Posts
    542
    Quote Originally Posted by Bunbury
    Quote Originally Posted by thyristor
    I don't want to complain, but isn't this a somewhat peculiar way to look at it?
    I would say that the water freezes when it has been in thermal contact with some body of a temperature below zero long enough to give off its latent heat - not in the reversed order.
    I also thought that the farmers placing barrels of water in their cellars, was because the large specific heat capacity of water would prevent great drops in temperature.
    I believe Janus is correct. The latent heat is released as the water freezes and this would help maintain a constant air temperature at 0degC until all the water is frozen. After that the heat capacity of the solid ice would probably help to slow the temperature drop.

    The corresponding reverse effect that's more intuitive would be evaporation of sweat from the skin. The latent heat of vaporization cools the skin.
    What I mean is that the latent heat isn't released as the water freezes, the water freezes as the latent heat is released. The freezing of water does, as far as I know but I may very well be wrong, not work in the same way as the solidification of the compounds in heat bags. There, the solidification is initiated by adding the initiation energy to it, and here you could really say that it gives off its latent heat as it freezes.
    373 13231-mbm-13231 373
    Reply With Quote  
     

  10. #9 Re: Where does freezing water get its kinetic energy from? 
    Forum Freshman
    Join Date
    Jan 2010
    Posts
    23
    Quote Originally Posted by Gen1GT
    We all know water expands as it turns to ice. This expansion can be enough to break water storage vessels, like water bottles. If the energy is being taken away to freeze the water, where does the energy come from to break a bottle?
    The water contains more energy than the ice in one kilogram. When water freezes, it releases its energy, one kind of which is to work to the environment. The mechenism that rules the solification is not to make sure the energy minimizes but the chemical potential minumizes, for the pressure remains. And this mechanism forces the phase transition occure.
    Reply With Quote  
     

  11. #10  
    Forum Freshman
    Join Date
    Jan 2010
    Posts
    9
    Ice (solid H2O) is less dense than water (which is why ice floats). The reason for this has to do with the molecular structure of water. Ice is what is called a "true solid"; meaning it has a crystal lattice structure. Obviously, when water is in its liquid form, there is no crystal lattice/structure.

    When water begins to freeze, the molecules space apart just enough to create a hydrogen-bond attraction - between hydrogen atoms of one molecule to oxygen atoms on the other molecule - and create a crystal lattice. This is why water expands and this is the cause of the container breakage....from water forming a lattice structure.

    Where does the energy come from?
    The answer is attractive forces (magnetic) between the molecules themselves. Water molecules are polar; meaning they have a positive side and a negative side. When the crystal lattice arranges itself during freezing, it is easier for the molecules to settle and form a lattice structure.

    Although the release of energy has SOMETHING to do with it, it doesn't affect the container to the point of breakage....in my opinion.
    Reply With Quote  
     

  12. #11 Re: Where does freezing water get its kinetic energy from? 
    Reptile Dysfunction drowsy turtle's Avatar
    Join Date
    Mar 2009
    Location
    UK
    Posts
    2,256
    Quote Originally Posted by shckm2686
    The water contains more energy than the ice in one kilogram.
    Just one little nit-pick, but one kilogram exactly of any substance has exactly the same amount of energy (e=mc^2). It is more correct to say that one mole of water has more energy than one mole of ice.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
    Reply With Quote  
     

  13. #12  
    Reptile Dysfunction drowsy turtle's Avatar
    Join Date
    Mar 2009
    Location
    UK
    Posts
    2,256
    Quote Originally Posted by Reaper
    The answer is attractive forces (magnetic) between the molecules themselves
    Electric, actually, rather than magnetic, but otherwise

    Quote Originally Posted by Reaper
    Although the release of energy has SOMETHING to do with it, it doesn't affect the container to the point of breakage....in my opinion.
    As the water crystallises, the polar regions allign themselves into such a pattern as to hold the minimum potential energy in the molecules. Decreasing the potential energy means work is done by the water; giving the water kinetic energy which, in an unconfining vessel, would be lost mostly as heat. In an enclosed space, on the other hand, the kinetic energy goes into breaking the container, or if the container is too strong, then the molecules cannot allign to start with, so this latent heat cannot be released. Therefore, the water will not freeze under pressure, although it will become very viscous.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
    Reply With Quote  
     

Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •