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Which statement applies to boiling but not to evaporation?

  1. Nov 16, 2013 #1
    "Which statement applies to boiling but not to evaporation?"

    1. The problem statement, all variables and given/known data

    Which statement applies to the boiling but not to the evaporation of a liquid?

    A The separation of the molecules increases greatly
    B At normal atmospheric pressure, the process occurs at one temperature only.
    C Energy must be provided for the process to happen.
    D All the bonds between molecules in the liquid are broken.

    2. Relevant equations

    None.

    3. The attempt at a solution

    I don't know, but to me B C D are all correct.

    A is incorrect because: Boiling-Yes, Evaporation-Yes

    B is correct because: Boiling-Yes, Evaporation-No (because occurs at all temperature)

    C is correct because Boiling-Yes (supply heat to boil), Evaporation: No (Molecules with higher kinetic energies will just escape, no need to supply any energies to them)

    D is correct because: Boiling-Yes (boiling occurs throughout the whole liquid, so all bonds broken), Evaporation-No (because I think that since only the fastest molecules escape, so it should not be "ALL bonds are broken".)

    Can someone teach me about this? Thank you.
     
  2. jcsd
  3. Nov 16, 2013 #2

    Simon Bridge

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    It does not ask you which are correct though does it?
    It asks: Which statement applies to the boiling but not to the evaporation of a liquid?
    i.e. which ones are boiling-yes and evaporation-no?
     
  4. Nov 16, 2013 #3

    D H

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    There's only one that has a "yes/no" answer.

    With regard to C, why do you sweat? With regard to D, I think it was asking about the water that has boiled or evaporated off. (Besides, boiling is not explosive. It doesn't happen all at once. I ccan turn off the heat to a pot of boiling water and it stops boiling.)
     
  5. Nov 16, 2013 #4

    haruspex

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    Because evaporation is a relatively slow process, you seem to have interpreted that side as merely some of the liquid evaporating. So you conclude evaporation does not satisfy D, and by imagining that the SVP at the liquid's initial temperature is above the ambient vapour pressure, some evaporation will occur without external input. OTOH, you've interpreted boiling as boiling all the liquid away. If you interpret evaporation as complete, you'll get different answers.
     
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