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Homework Help: Viscosity of Honey decreases. But why?

  1. Apr 8, 2005 #1
    For AS Level physics I had to do some coursework on the viscosity of Honey. I found out that as the temperature of the honey increases, its viscosity decreases.

    I drew the conclusion that, when a substance is heated, its molecules move farther apart and faster, so therefore, if the molecules are moving farther apart, the substance will expand. This reduces the density of the Honey and lowers the viscosity, allowing the ball-baring to fall through the Honey faster.

    However, I have been told this is not the actual reason for why the viscosity of the honey decreases, and that it has something to do with Helium atoms (in other words, ask a chemist).

    Can anyone tell me why the viscosity decreases?

    I’ve been stuck on this for a while and ill be grateful for any help.


  2. jcsd
  3. Apr 8, 2005 #2
    Please explicate how reduction in density implies reduction in viscosity. Better yet, show a derived equation where viscosity is proportianal to density.

    I don't think we need to deal with He atoms to explain this effect.
  4. Apr 8, 2005 #3


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    Viscosity (talking about liquids) is a function of the cohesive bonding forces present in the substance. Since in a liquid, the cohesive bonds are pretty high, the fluid has a hard time allowing adjacent layers "slip" past one another (think of pushing a stack of playing cards from the top). It all goes to intermolecular forces.

    Now, I am no honey expert or chemist, but I was surprised to see helium as your clue. I was under the impression that honey is a complex sugar which is carbon, hydrogen and oxygen of course there is water in there as well. I have no idea where the helium is coming from. Perhaps someone else can elaborate on that.

    That also reminds me, I would note in your analysis two other items:
    1) The viscosity of honey has to be dependant on how much water is in it.
    2) I don't have any sources to prove or disprove, but I would be cautious in considering honey to be a Newtonian fluid (I don't know if you really need to go that far into this, but I thought I'd mention it).
    Last edited: Apr 8, 2005
  5. Apr 8, 2005 #4


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    I'd imagine that NuGG's clue was 'hydrogen', rather than 'helium' as he has stated.

    NuGG, do a bit of reading on hydrogen bonding and see if you get anywhere.
  6. Apr 8, 2005 #5


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    I'd say that you're in the ballpark, and am very puzzled by whoever is asking you to look at "helium atoms". Fred has given you a pretty good answer that I would agree with (that's why it's good! :)). In addition, here's a link for you to read all about viscosity more than you would ever care for:


  7. Apr 9, 2005 #6
    Sorry i think it was hydrogen actualy. My mistake.
  8. Apr 9, 2005 #7
    Ive done some more reserch and added some information on cohesive bonds etc to my conclusion, however i still cannot find anything useful for Hydrogen atoms. I presume it has something to do with the Hydrogen bonds...

    Any one got any ideas?


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