Time for water to boil at altitude?

Discussion in 'Computer Support' started by Dribbler, Oct 7, 2004.

  1. Dribbler

    Dribbler Guest

    Watching a TV programme about the Himalayas, they mentioned water takes
    longer to boil at altitude.
    Why is this? I think it must be something to do with pressure, but why and
    what is the principal?
    Thank you,
    Dribbler
     
    Dribbler, Oct 7, 2004
    #1
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  2. Dribbler

    Ron Martell Guest

    Did they say it takes longer to get water to boil, or did they say
    that you have to boil things longer at high altitudes?

    The reduced air pressure means that water will boil at a lower
    temperature at high altitude. And once it reaches the boiling point
    it will not get any hotter - just boil faster.

    The lower boiling temperature means that things take longer to cook.
    So pasta that cooks in 10 minutes at sea level might require 12
    minutes or more to cook properly in boiling water at high altitude.


    Ron Martell Duncan B.C. Canada
    --
    Microsoft MVP
    On-Line Help Computer Service
    http://onlinehelp.bc.ca

    "The reason computer chips are so small is computers don't eat much."
     
    Ron Martell, Oct 7, 2004
    #2
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  3. Homework?
    http://www.newton.dep.anl.gov/askasci/phy00/phy00162.htm
     
    =?ISO-8859-1?Q?R=F4g=EAr?=, Oct 7, 2004
    #3
  4. Dribbler

    Liz Guest

    This is because the air pressure is lower at high elevations.
    Water at sea level boils at 100C and freezes at 0 degrees.
    At higher elevations, where atmospheric pressure is lower,
    water's boiling temperature is lower, so it takes longer to
    boil or cook things.
     
    Liz, Oct 7, 2004
    #4
  5. Dribbler

    Kenny Guest

    It boils at a lower temperature at altitude.

    Boiling occurs when the water is hot enough to have the
    same pressure as the surrounding air, so that it can form bubbles. As water
    is heated, its steam pressure rises, until it reaches the pressure of the
    surrounding air. At high altitudes, this air pressure is lower than at sea
    level, so the water doesn't have to get so hot to get to boiling.
     
    Kenny, Oct 7, 2004
    #5
  6. Dribbler

    Dribbler Guest

    Thankyou Kenny, you explain it so well!
    I appreciate all the replies, I feel rather daft for not knowing and for
    not being able to locate the answer myself on Google.
    Thanks!
    Dribbler
     
    Dribbler, Oct 7, 2004
    #6
  7. Dribbler

    Conor Guest

    Did you actually read that? The boiling point is lower thus requiring
    less heating up but it takes longer?
     
    Conor, Oct 8, 2004
    #7
  8. Dribbler

    Plato Guest

    Since a watched pot never boils put a lid on it.
     
    Plato, Oct 8, 2004
    #8
  9. Dribbler

    alan Guest

    I saw that too. It's wrong, or at least badly expressed Water will reach
    its boiling point quicker at altitude because the boiling point is reduced -
    lets say it boils at 95 rather than 100C. Food boiled at 95C will take
    longer to cook than at the normal 100C.

    Alan
     
    alan, Oct 8, 2004
    #9
  10. Dribbler

    Liz Guest

    Do you have trouble understanding food takes longer to cook
    at a lower temperature?
     
    Liz, Oct 8, 2004
    #10
  11. That explains why a pressure cooker cooks much faster.
    :)
     
    =?ISO-8859-15?Q?Brian_H=B9=A9?=, Oct 8, 2004
    #11
  12. Dribbler

    Old Gringo Guest

    Here is the fun part: http://www.biggreenegg.com/boilingPoint.htm
     
    Old Gringo, Oct 8, 2004
    #12
  13. Actually, it's just badly expressed.

    Water boils at a lower temperature at altitude as you say, so if
    boiled on a normal domestic stove would actually boil quicker, but on
    the mountainside, they normally use small hexamine or spirit stoves
    with lower heat output, and there is usually wind that takes away lots
    of the small amount of heat generated, so YES, it usually does take
    longer to boil at altitude, even though it boils at a lower
    temperature.

    And YES, it will also take longer to cook after boiling, because the
    temperature is lower.

    And yes, a cup of tea made at very high altitude tastes ghastly!
     
    Peter Wilkins, Oct 8, 2004
    #13
  14. I am not sure if I have trouble understanding food takes longer to
    cook at a lower temperature.
     
    Lady Chatterly, Oct 9, 2004
    #14
  15.  
    Franz Heymann, Oct 9, 2004
    #15
  16.  
    Franz Heymann, Oct 9, 2004
    #16
  17. No. At the top surfce of the water, its pressure is always exactly
    equal to the atmospheric pressure.
    What you meant to say is that it boils when its vapour pressure
    becomes equal to that of the atmosphere.

    [snip]

    Franz
     
    Franz Heymann, Oct 9, 2004
    #17
  18. Dribbler

    Liz Guest

     
    Liz, Oct 10, 2004
    #18
  19. Dribbler

    Liz Guest

    Then you'll need a computer science degree to use a microwave oven.
     
    Liz, Oct 10, 2004
    #19
  20. Dribbler

    Liz Guest

    Liz, Oct 10, 2004
    #20
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