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Please settle a discussion

  1. Sep 12, 2006 #1
    Here's the issue in question. Let's say you had two equally sized pans filled with equal amounts of water. The only difference between them is the water in one pan is 50 degrees while the other is 100 degrees. Next, they are put on the stove with equal flame applied, would the pan with 100 degree water come to a boil first or would they both come to a boil at the same time.
     
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  3. Sep 12, 2006 #2

    Hootenanny

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    Welcome to the Forums,

    The 100oC pan would boil first. Do you require an explantion or is a yay or nay enough?
     
    Last edited: Sep 12, 2006
  4. Sep 12, 2006 #3
    The pan at 100 degrees (celcius or farenheit) would come to boil first. Classical heat equation Q=C*dT.
    They both have the same mass and are both water so their heat capacity is the same. The heat energy applied to both (from the flame) is the same. So the temperature should go up at a similar rate in each. Since the 100 degree pan has distance to travel in this regard, it will reach boiling temperature first.
     
  5. Sep 12, 2006 #4
    No, no equations necessary, you can solve this without knowing any science!
     
  6. Sep 12, 2006 #5

    Hootenanny

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    I feel a practical investigation coming on...:rolleyes:
     
  7. Sep 12, 2006 #6
    Bring It Baby! :devil:
     
  8. Sep 12, 2006 #7
    If they were both 100F, they would both take the same amount of time to boil, agreed?

    So if the one that is 50F has to first go to 100F, the only way it can be faster is if it takes negative time to boil from 50 to 100, and that ant gonna happen. See, no equations!
     
  9. Sep 12, 2006 #8

    DaveC426913

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    Not only is it intuitively obvious that the pan with near-boiling water will boil first, but you can prove that it makes no sense otherwise.

    Say a pan50F takes 10 minutes to boil.
    We'll postulate that pan100F also takes 10 minutes.

    So, now what happens when pan50F reaches 100F? It will now take 10 minutes from that point to boil. Which means it actually took 20 minutes in total. Which would mean 10=20!

    Which is impossible, therefore the initial postulate can't be true.
     
    Last edited: Sep 12, 2006
  10. Sep 12, 2006 #9

    Gokul43201

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    I've got one word for you: Mpemba!
     
  11. Sep 12, 2006 #10
    I've got one for you, prove it! :wink:
     
  12. Sep 12, 2006 #11

    berkeman

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    No, no. It's a trick quesion. The OP craftily didn't specify whether the temperatures were in C or F. The 100C pan is already boiling before it is put on the stove, so neither answer is correct!
     
  13. Sep 12, 2006 #12

    NoTime

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    Boiling usually means that the water is turning into water vapor at a great rate.
    At a lower rate its called simmering.
    In any event 100c water isn't boiling without a heat input cause it would get less than 100c instantly.

    Err, in a pan it's going to get colder instantly anyway:smile:
     
  14. Sep 12, 2006 #13
    Water boils at a temperature slightly greater than 100C, despite popular belief. It has to be >100C for nucleation and bubbles to form.

    "Simmering" is not a proper term, as far as I am aware.
     
    Last edited: Sep 13, 2006
  15. Sep 12, 2006 #14

    NoTime

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    My speel checker finds "Simmering" :wink:

    If you want to get picky then it boils at room temp.
    Otherwise, it would never evaporate :smile:
     
  16. Sep 12, 2006 #15
    Ehh? That's equally wrong as well....water vaporizes(well, evaporates) at room temp, it does NOT boil.
     
    Last edited: Sep 12, 2006
  17. Sep 12, 2006 #16

    NoTime

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    It's all about the semantics, a room, at room temp, does have some heat :smile:

    v., boiled, boil·ing, boils.
    To change from a liquid to a vapor by the application of heat
     
  18. Sep 12, 2006 #17
    No, its not. Arg.....you need to get a book on thermodynamics.

    Boiling is for a solid-liquid interface.

    Evaporation occurs at the liquid-vapor interface

    Now, no more misuse of words. :smile:
     
    Last edited: Sep 12, 2006
  19. Sep 12, 2006 #18

    NoTime

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    :rofl: Is that an oxymoron, or what?
     
  20. Sep 12, 2006 #19
    What.......? :confused:

    Do you think it all boils instantly into a vapor?
     
  21. Sep 12, 2006 #20

    NoTime

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    I don't know what planet your thermodynamics book came from, but ...

    Most people think that what occurs at the interface between liquid and solid is melting. :biggrin:
     
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