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Homework Help: Frozen and liquid kerosene difference?

  1. Jan 15, 2010 #1
    1. The problem statement, all variables and given/known data
    a ball made of keroseneis put into a liquid kerosene.What happens?


    2. Relevant equations
    ball descends
    ball floats
    ball hovers
    first descends, then ascends.

    3. The attempt at a solution

    can anyone halp me what kind of kerosene thing is and explain the behaviour of kerosene ?
     
  2. jcsd
  3. Jan 15, 2010 #2

    ideasrule

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    I'm guessing that this ball is made out of solid kerosene? What do you know about buoyancy? When does something float and when does it sink?
     
  4. Jan 16, 2010 #3
    I don't know.
    It's totally this!

    I think it's solid and then frozen kerosene and it's put into a just solid one....

    ?
     
  5. Aug 18, 2010 #4
    I ran into this question as well and could not find any definitive answer.
    It obviously has to do with densities. How dense is frozen kerosene compared to liquid kerosene (810 kg/m3)?
    Now with water (atypical) frozen water is less dense than liquid water thence it floats however many substances become more dense when the lose energy and effectively contract thereby becoming more dense. I don't know however what happens with Kerosene.
    Any reliable answers would be gratefully received :confused:
     
  6. Aug 26, 2010 #5

    presbyope

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    The really interesting question is what is the difference between floating in kerosene and hovering in kerosene? Seriously, if 3 of the 4 answers are silly, that's a good indication what the correct answer is.
     
  7. Aug 26, 2010 #6
    I think you're right with the assumption that floating and hovering are spurious answers. But I haven't been able to find anywhere that mentions whether Kerosene acts like conventional liquids or other. As I said before my assumption is that as it freezes it would contract and become more dense thereby dropping to the bottom of the liquid. Do you know anywhere that I might find a more definitive answer?
     
  8. Aug 26, 2010 #7
    However If you put a ball of most substances into a liquid form of those substances they would probably sink and absorb latent heat from the liquid until they melt. The only reason that it would rise and hover or float would be if it had air trapped in it when the ball was made which I presume isn't the case. I suppose the nub of the question remains is: Does Kerosene act like water or most other substances. If the latter, then a) is the answer
     
  9. Aug 26, 2010 #8

    presbyope

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    Sorry I don't have empirical data about the density of solid kerosene. But kerosene is just a mixture of ~C6-C16 hydrocarbons, so I wouldn't expect any exotic behavior. Water expands because the hydrogen bonds in ice are so long (276 pm according to google).

    Maybe you could look for density data on hexane, octane, etc?
     
  10. Aug 26, 2010 #9

    presbyope

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    You could try freezing it if you had some liquid nitrogen. Apparently kerosene forms a gel because the melting points of the components are spread over a big range. To freeze it completely I would guess you'd have to go below the melting point of hexane around -96C. But nitrogen boils at -196C so that's no problem.
     
  11. Aug 26, 2010 #10
    So if Kerosene is a compound of many different substances...would it not be possible that as these melt at differing temperatures it could cause the ball to rise and float..like wax on liquid wax?
     
  12. Aug 26, 2010 #11

    presbyope

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    Well that's a fascinating idea. Can you give more details? The thing is, the heavier hydrocarbons would melt last, so they would still be denser than the liquid kerosene.

    I thought things "hovered" on wax because of the high surface tension. In which case they would sink like a water strider on water if the surface tension was broken.

    .. found some information on waxes. It sounds these folks are really, really sad that they can't find a hydrocarbon that expands when it freezes. Beeswax comes close apparently.

    http://www.howtomakecandles.info/cm_article.asp?ID=CANDL0401
     
  13. Aug 26, 2010 #12
    I stand corrected...thanks for the info though, seems I have my answer now at least...
     
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