Why is the boiling point of water less than a hundred degrees celsius at higher altitudes?

1 Answer
anor277
Apr 2, 2018

Well, what is the definition of #"boiling point?"#

Explanation:

The boiling point of a liquid are the conditions of temperature and pressure when the vapour pressure exerted by the liquid is equal to the ambient pressure, and bubbles of vapour form directly in the liquid.

And thus the vapour pressure of water at #100# #""^@C# is #1*atm# BY DEFINITION. If the ambient pressure is reduced, then as a consequence the temperature of the boiling liquid will also be reduced. And such is the principle of vacuum distillation, when a liquid that is involatile at normal pressure, will be volatile at a LOWER external pressure.

At higher altitudes, the ambient pressure is reduced...and so is the boiling point. The boiling point of water on top of Mt Everest is #69# #""^@C#. Why so?

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