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Homework Help: Liqiud and solid

  1. Feb 26, 2009 #1
    1. The problem statement, all variables and given/known data

    hi all, i just have a small quistion that why always the water is down and ice starting from the up or the top?
    i mean for example if we try to freezing a water the ice will start from the top of the bottle and the water will be downsizing in the bottom of the buttle until it become all solid

    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Feb 26, 2009 #2

    Mapes

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    Hi looody, welcome to PF. At 0°C, liquid water is denser (heavier) than ice.
     
  4. Feb 26, 2009 #3
    Does it happen that way? I guess I've never watched water freeze for long enough :tongue:

    Here"s what I think is happening: The density of water at nearly freezing point is lower than that of water at room temperature and the density if ice is lower than water (that's why ice blocks float in your cool drink). So, the colder water rises and eventually freezes at the top of the other water.
     
  5. Feb 26, 2009 #4
    In fact water has its maximum density at a temperature of 3.98 Degrees. Imagine ponds ,lakes etc froze from the bottom up,what would that do to the pond life?Isn't nature clever?
     
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