# Boiling an egg at high altitude

## Homework Statement

an egg boiled for 4 minutes at the top of a mountain does not harden

## The Attempt at a Solution

pressure is lower at the top of a mountain than at sea level. Is the issue here the fact that pressure inside the egg does not build up sufficiently to harden it at the top of the mountain where in fact, it's necessary to use temperatures greater than 100 degrees Celsius to cook it

mgb_phys
Homework Helper
Not quite.
Whats the highest temperature you can heat water to (in an open container)
What happens to this temperature at altitude?

the highest temp for water in an open container is 100 degrees Celsius and I don't know what happens to this temp at altitude

DaveC426913
Gold Member
the highest temp for water in an open container is 100 degrees Celsius and I don't know what happens to this temp at altitude
As an extreme: how hard is it to boil water in outer space? Why?

no density and no pressure in space
apparently, time X temp cooks the egg
lower temp at high altitude requires more time

DaveC426913
Gold Member
It sounds like you Googled it. Do you understand it?

Well, I do get the concept of never something for nothing and balancing a loss of temperature with an increase in amount of time needed to cook the egg.

Hey man, it's good of you to ask though.

mgb_phys
Homework Helper
The highest temperature you can get is boiling point (which is 100C at sea level)
Boiling point decreases with altitude, an easy way to remember this is to imagine the weight of air holding the water in the liquid - at lower pressure it's easier for the water to escape as steam and so the boiling point is lower.

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In simple terms - Yes it's possible to boil at egg at altitude, however, it will take longer for the water to boil the egg hence acknowledgement of low pressure and less oxygen.

DaveC426913
Gold Member
So, in summary, the critical bit to understand in this whole thing is that, at lower pressure water boils at a lower temperature. So, your water might only reach 90C and won't get any hotter. It's still boiling, but the egg isn't cooking as much.

You guys are close. Cooking is a heat transfer problem. To make heat go from the hot object (boiling water) to the cold object (egg) you need a temperature difference (Th-Tc). Since water's boiling point temp is reduced at altitude, the rate of heat transfer (proportional to Th-Tc) is less. This is complicated by the fact that cold temperature TC is increasing the longer the egg is in the water.. but it will never surpass hot temperature Th.

DaveC426913
Gold Member
You guys are close. Cooking is a heat transfer problem. To make heat go from the hot object (boiling water) to the cold object (egg) you need a temperature difference (Th-Tc). Since water's boiling point temp is reduced at altitude, the rate of heat transfer (proportional to Th-Tc) is less. This is complicated by the fact that cold temperature TC is increasing the longer the egg is in the water.. but it will never surpass hot temperature Th.
Not sure why you need to make it more complicated. If the water never reaches 100C, it's pretty straightforward that the egg will take longer to cook.

Borek
Mentor
Or - if you are high enough - egg will never cook. If memory serves me well somewhere below 20 km water boils at about body temperature. At 36.6 deg C egg can start to stink quite fast, but it won't solidify.

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mgb_phys