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I Water heaviest at 4 degrees

  1. May 2, 2016 #1
    I know that water is the most dense at 4 degrees celsius. That's why water at the bottom of a sea has that temperature. But how did it get that temperatur in the first place and why does the energy not distribute itself in such a way that the temperature is the same throught? Is it the particles that have a temperature of 4 degrees that sinks to the bottom or is it the pressure at the bottom that makes the water more dense?

    What if a sea is surrounded by constant weather condition and constant atmospheric temperature. How would the temperature distribution look like as a function of altitude under water? If the surrounding temperature is 20 degrees, would the water at the bottom if it is deep enought still be 4 degrees?
  2. jcsd
  3. May 2, 2016 #2

    jack action

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    The reason water is denser at 4°C is because of the particular way molecules are disposed with respect to other at that temperature.

    Molecular disposition of ice (voids are present):

    Molecular disposition of water (voids are filled):

    There's good reading on Wikipedia:
    Heat goes from hot to cold, no matter what, until equilibrium is reached. So in theory, in a constant environment, given enough time, water - or any other substance - will reach a uniform temperature.

    But the ocean is far from being surrounded by a uniform temperature (top and bottom) and there are lots of currents adding variables to the mix.
  4. May 3, 2016 #3


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    The planet isn't the same temperature all over, it's colder near the poles and warmer at the equator. Google the Great Ocean Conveyor Belt.


    This effect works to chill the ocean floor faster than other mechanisms can heat it.

    Edit: or perhaps I should say it chills the ocean floor at roughly the same rate as other mechanisms can heat it. If you ignore man made global warming then the system is roughly in equilibrium.
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