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Thinner than water?

  1. Apr 20, 2005 #1

    DaveC426913

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    Is there a liquid that is thinner than water?

    I know there are liquids that will float on water (such as oil) but they are still thicker. If you took a swim in a pool of oil, you'd have a hard time moving about. Is there a liquid that is easier to move in than water (while still remaining below vapourization point)? Maybe liquid hydrogen, helium, nitrogen or oxygen, since they're lighter molecules. But anything that isn't super-cooled?
     
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  3. Apr 20, 2005 #2
    Salt dissolved into water makes it easier to swim in. I think anything that dissolved into water to make it denser would make it easier to swim in.

    Thinner? As in having a smaller molecule and still being liquid at room temperature?
     
  4. Apr 20, 2005 #3

    chroot

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    You want a liquid with a lower viscosity than water? How about alcohol (either ethanol or isopropanol)?

    - Warren
     
  5. Apr 21, 2005 #4

    DaveC426913

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    No. Salt dissolved into water makes it easier to float in (i.e. more bouyancy). But additives such as salt will, as you point out, make it denser, and thus harder to swim through.
     
  6. Apr 21, 2005 #5

    DaveC426913

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    Yeah, I was wondering about that. I wonder what it would be like (assuming you survived) to swim in alcohol. Would it feel light? Would the ripples be higher? faster?
     
  7. Apr 21, 2005 #6

    ZapperZ

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    What do you exactly mean by "thinner"?

    If you mean "viscosity", then chroot has given you a nice example. And if you want to go all the way with this, then why not pick superfluid helium that has zero viscosity?

    Zz.
     
  8. Apr 21, 2005 #7
    A person can't float in anything less dense than water. They would sink to the bottom. A liquid can be very dense and not be very viscous. Imagine how you could swim on top of a pool of mercury. (I wouldn't recommend it). Mud would be less dense than mercury but would be much more viscous and more difficult to swim through, while a person couldn't swim in alcohol or oil for very long at all.
     
  9. Apr 21, 2005 #8

    siddharth

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    Why is that?
     
  10. Apr 21, 2005 #9
    Humans are mostly water. We have pretty much the same density as water, slightly more or less depending on how much air is in our lungs. In a liquid less dense than water, we'd be more dense than that liquid too, so we'd sink.
     
  11. Apr 22, 2005 #10

    siddharth

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    Actually while floating, our body is not fully immersed. There is still some part which is outside the water. That means that we can float in a liquid which is of a lesser density
    than water, with a greater portion of our body being submerged.

    So does anyone know the density of the human body while floating? That is assuming that his lung is at full capacity, how much of the human body floats above water?
     
  12. Apr 22, 2005 #11
    I almost wrote that the more of our body is out of the liquid the more difficult it would be to float and that struck me as flawed logic. Then I saw what made me think that.

    The density of the human body varies from person to person. Muscle density and amount of fat and lung capacity all vary.
     
  13. Apr 22, 2005 #12

    brewnog

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    Generally, women are much better at floating than men due to a higher proportion of body fat (and we all know that fat is less dense than water...).

    As an aside, women float naturally on their backs, men on their fronts.
     
  14. Apr 22, 2005 #13
    Water does not compress very easily. It is used to test some high pressure hydraulic systems. After filling a tank with water at a pressure greater than the maximum working load a hammer is used to tap on the tank. If the tank cracks the water will not shoot from the tank with much force because its volume was not signifcantly reduced. (any air bubbles could be dangerous.) If that same tank were tested with oil then the force of the oil shooting out could kill a person.

    The same principle is true for tidal waves or tsunamis. A wave loses very little momentum as it travels. It can travel thousands of miles without losing momentum because it changes very little in volume.

    I would guess that the waves in a pool of alcohol would be initially higher because the material is less dense, but they would not travel as far or as fast if alcohol is more compressible than water.(I'm assuming it is.) Alcohol would feel light and anyone swimming in it would feel heavy and probably sink.
     
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