# Time for water to boil at altitude?

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

1. ### DribblerGuest

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

2. ### Ron MartellGuest

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.

--
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

3. ### =?ISO-8859-1?Q?R=F4g=EAr?=Guest

Homework?

=?ISO-8859-1?Q?R=F4g=EAr?=, Oct 7, 2004
4. ### LizGuest

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
5. ### KennyGuest

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
6. ### DribblerGuest

Thankyou Kenny, you explain it so well!
I appreciate all the replies, I feel rather daft for not knowing and for
Thanks!
Dribbler

Dribbler, Oct 7, 2004
7. ### ConorGuest

Did you actually read that? The boiling point is lower thus requiring
less heating up but it takes longer?

Conor, Oct 8, 2004
8. ### PlatoGuest

Since a watched pot never boils put a lid on it.

Plato, Oct 8, 2004
9. ### alanGuest

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
10. ### LizGuest

Do you have trouble understanding food takes longer to cook
at a lower temperature?

Liz, Oct 8, 2004
11. ### =?ISO-8859-15?Q?Brian_H=B9=A9?=Guest

That explains why a pressure cooker cooks much faster.

=?ISO-8859-15?Q?Brian_H=B9=A9?=, Oct 8, 2004
12. ### Old GringoGuest

Here is the fun part: http://www.biggreenegg.com/boilingPoint.htm

Old Gringo, Oct 8, 2004
13. ### Peter WilkinsGuest

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

I am not sure if I have trouble understanding food takes longer to
cook at a lower temperature.

15. ### Franz HeymannGuest

Franz Heymann, Oct 9, 2004
16. ### Franz HeymannGuest

Franz Heymann, Oct 9, 2004
17. ### Franz HeymannGuest

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
18. ### LizGuest

Liz, Oct 10, 2004
19. ### LizGuest

Then you'll need a computer science degree to use a microwave oven.

Liz, Oct 10, 2004
20. ### LizGuest

Liz, Oct 10, 2004