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Help understanding a lab - intermolecular bonding

  1. Jun 15, 2005 #1
    Hello, I have done an experiment and I am having trouble explaining why certain things happen.

    The topic is intermolecular bonding. I used three liquids, each is composed of different types of bonds.

    liquid 1) Hydrogen bond
    liquid 2) bonding due to dipole forces
    liguid 3) bonding due to Van der Waals forces

    Basically I take a liquid, put it in a cup and stir it really fast. I record the depth of the maximum vortex and the amount of time that it lasts.

    Then do the same with the other two liquid. (same amount, same container).


    Now, I have 3 different values for the amount of time the vortex lasts, and I'm trying to understand why (in terms of intermolecular bonding). The answer that comes to mind is viscosity, but it is nowhere in the course.. so I dont think thats what I'm supposed to be looking for.

    My second question is why is water (hydrogen bonding) so much different than the other two in terms of the depth of the vortex?

    I know that hydrogen bonding is the strongest, but I'm not sure how that piece of information applies to the vortex.. as no bonds are being broken.

    thanks for any help
  2. jcsd
  3. Jun 15, 2005 #2
    Am I to assume that the liquid that hydrogen bonds has a deepest vortex???

    The Bob (2004 ©)
  4. Jun 15, 2005 #3
    EDIT: Ok something is wrong here.. so I'm doing the experiment again.

    I'll post the results as soon as I'm done
    Last edited: Jun 16, 2005
  5. Jun 15, 2005 #4
    Are you sure about these results? I only ask because I would expect the hydrogen bonding to cause the biggest vortex and but also to be the first to stop, which goes against what you have said.

    The explaination is that the strong forces would cause the molecules to get pulled to one side more (so big vortex) but also because of the forces it would slow down fastest because the pull would do that. However it could be that the attractive forces cause the molecule to pull against each other and this would suggest a smaller vortex and a longer time to settle because the molecules are being pulled by each other more than in van der Waal's.

    The Bob (2004 ©)

    Is that 0.5cm or what???
  6. Jun 15, 2005 #5
    yes that is 0.5 cm
  7. Jun 15, 2005 #6
    It is intersting. I would say that the dipole is the intermediate force and so is not at one end of the spectrum. This means will give the result it does. The other two are at opposite ends and so act in similar ways (e.g. hydrogen bonds are strong so attract more than van der Waal's but moving act in similar ways).

    The idea is in my head but I do not have the time (my dad's faylt) to write it down. Also some other people might give me some inspiration.

    The Bob (2004 ©)

    P.S. Time for bed :smile:
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