why does the boiling point of a liquid vary with the barometric pressure?

Answer 1

when boiling the energy needed to turn the water to its liquid phase is achieved. as it is achieve the some water molecules turn to vapor phase exerting pressure on the surrounding then boiling happens only when the vapor pressure of the liquid equalizes the barometric pressure....
however, when the barometric pressure is low then it can be easily reach by the vapor pressure of the liquid beacuse of that the liquid will boil even if the temperature is not its original boiling temperature....

best answer?

Answer 2

In order for a liquid to boil and become a gas, it must reach a point where the vapor pressure of the liquid is equal to the prevailing pressure above the liquid. That, in an open system, is the barometric pressure. At higher pressures, boiling point increases; at lower ones or under a vacuum, it decreases.

It has nothing to do with dissolved gases, as those are different species within the liquid.

Answer 3

The amount of gas that can be dissolved in a liquid is dependent on temperature and pressure. Boiling, by definition, is a state where the dissolved gases are being "forced out" of the liquid. So if the pressure is lower, the air will be forced out much more easily. And vice versa.

Answer 4

That's how we get "freeze Dried" stuff. Lower the pressure to close to zero and water boils at a very low temperature. If fruits were dried at a high temp their tastes and other properties change. By "boiling off the water" at a very low temp the fruit properties stay pretty well intact.