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How does water extinguish fire?

  1. Nov 16, 2004 #1

    MR

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    How does water extinguish fire? My 5-year-old brother asked me, and now I'm really curious.
     
  2. jcsd
  3. Nov 16, 2004 #2
    Fire needs two things: oxygen and fuel.

    Water cuts off access to oxygen, and cools the fuel to below combustion temperature.
     
  4. Nov 16, 2004 #3

    MR

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    OK, now I'm feeling REALLY ignorant...
    What's combustion temperature?
    Also, I've heard a number of times of using water as a cooling agent (especially in nuclear reactors), but why does water cool things down so well?
    Thanks!
     
  5. Nov 16, 2004 #4
    water has a high specific heat, meaning it takes a lot of energy/heat to increase the temperature of 1 gram of water by 1 degree Celcius
     
  6. Nov 16, 2004 #5

    russ_watters

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    Staff: Mentor

    Make that 3 things: oxygen, fuel, and heat. Your description has all 3.

    MR, when you strike a match, you are using friction to increase the temperature of the phosphorous on the match head above its ignition temperature - the temperature at which it starts to burn. After it starts to burn, it expends more energy than is needed to keep the fuel burning - so it stays lit.

    Welcome aboard!
     
    Last edited: Nov 16, 2004
  7. Nov 16, 2004 #6
    right, heat. i always make that mistake. I figure if you're talking fire, heat's pretty much a given.
     
  8. Nov 16, 2004 #7

    MR

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    Thanks, people...This is so cool!
     
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