Question

What would happen to the boiling point of water at $8,000\;m$ above sea level, where air pressure is lower?

Answer 1

As we know that boiling point is a physical property of a compound. The boiling point is defined as the temperature at which the compound’s vapour pressure reaches the pressure of the atmosphere. So the air pressure is lower. We know that at higher altitudes, the substance boils faster than at sea level.

Complete Step By Step Answer:
We know that the boiling point of water is $100^\circ C$ . So this is valid at sea levels too and is subject to change under various conditions.
We know that above $2500\;feet$ , the atmosphere becomes much drier. There is less oxygen and atmospheric pressure.
We need to add energy in the form of heat to boil water. They start to break the bonds binding them together as energy is transferred to the water molecules. Because as soon as its inner vapour pressure approaches the pressure exerted by the atmosphere in it, the water will boil or turn to vapour. Bubbles will start to form as that happens and the water boils.
So it will require less energy to get water to the boiling point if the atmospheric pressure is lower, or at a higher altitude.
We can say that the boiling point will be lower because when water boils the vapour pressure is equal to the atmospheric pressure.
Hence if we are at $8000\;m$ above sea level, the air pressure is lower than one pressure and the equilibrium between the water and air pressure will be reached before.

Note:
We can also compare this with an example, as the atmospheric pressure at the top of Mount Everest is $0.36\;atm$ . So if we plan to boil water there, it is likely to boil much faster at that altitude. We should know that Earth’s atmosphere has a huge reservoir of gas, due to the earth’s gravity exerts pressure on the earth’s surface. We should note that this atmospheric pressure is measured by a simple instrument called ‘mercury barometer’.