Water boils at 100 degrees Celsius at sea level, but far lower high up a mountain.

The longer version

Boiling happens when the vapour pressure inside a liquid matches the pressure pushing down on its surface. At sea level the entire weight of the atmosphere presses on the water, so molecules need considerable energy to escape as a gas. Higher up there is far less air above, the pressure drops, and molecules break free at a noticeably lower temperature.

That limit changes how food behaves. Water cannot climb above the temperature at which it boils, so a pot on a high peak stays cooler than one at the coast. Pasta, rice and eggs therefore take longer to soften in thin air, which is one reason recipes written for low ground need extra time.

Where this entry sits

Everyday physics and chemistry hide small wonders in plain sight, from kitchen reactions to the light in the sky. These short facts explain matter, energy, electricity, magnets, sound, and the simple units we use to measure the world. The full list sits on the Science and Physics page, where every entry is listed in order.