Does water’s boiling point change with altitude?

Water’s boiling point depends on pressure, so yes, it changes with altitude or depth. At sea level, where the pressure is 1013 hectopascals (hPA), the boiling point is 100°C. At the peak of

Mount Everest, an altitude of 8848m, pressure is 335hPa and the boiling point 71°C. On the Mariana Trench floor, 11km below sea level, the boiling point rises to 180°C.

As water is heated, more molecules evaporate, creating a rising vapour pressure, and when the vapour pressure reaches the pressure of the surroundings, the water boils. Up a mountain, the water’s vapour pressure need only match the lower external pressure at altitude, so the water boils earlier, at a lower temperature. Far more energy is required to boil water under higher external pressures.

The higher your location, the faster you can make water boil, because the atmospheric pressure is reduced with altitude.