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Why Does Density Affect the Density of its Container?

  1. Aug 7, 2015 #1
    I've never been able to figure this out. I can understand when you put oil in water that one floats on top of the other, but why does it still work if I put it into a balloon? Something that keeps it from directly interacting with the medium it's in?
     
  2. jcsd
  3. Aug 8, 2015 #2

    mfb

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    Why should oil and water behave differently in a balloon (compared to what, a bucket)? The heavier medium feels a greater force per volume to go downwards, so energy can be released by the separation.
     
  4. Aug 8, 2015 #3
    Sorry I didn't clarify, I meant in a atomic level, what is happening that causes buoyancy?
     
  5. Aug 8, 2015 #4

    mfb

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    The force differences. It doesn't matter at which scale you look at it.
     
  6. Aug 8, 2015 #5

    sophiecentaur

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    Forgetting about floating and sinking, which are macroscopic issues, the definition of density is the same on any scale.
    Density = Mass per unit volume
    You get the same answer if you are dealing with a bucket sized sample or a single, whole molecule. Looking inside a molecule, the Mass is not distributed uniformly so the dense bits will be the nuclei and there will be ( mostly) empty space in between occupied by some electrons.
    When your substances are fluids, on the ground, the more dense substance will fall down and displace the less dense. That is a universal rule unless there is some chemical reaction between the two substances.
     
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