How does the boiling point of water change as altitude increases?
As the altitude increases the boiling point of water decreases.
Water boils at lower temperatures at higher elevations. The air pressure at higher elevations is less. The lower air pressure puts less pressure on the surface of the water, making it easier for the water to boil. When the kinetic energy of the water molecules creates pressure equal to or greater than the air pressure the water boils.
Temperature is an indirect measure of kinetic energy so if the kinetic energy needed for the water to boil is less the temperature of boiling is less. So if there is less air pressure pushing on the water is less it requires less energy for the water to boil.
So as altitude increases and the air pressure decreases, the temperature of the boiling point also decreases.