Boiling Point
The temperature at which the vapour pressure of a liquid equals the external pressure acting on it.
Formula / equation
p_vap = p_external
Unit
°C
In depth
Because boiling requires the vapour pressure to match the surroundings, it happens at lower temperatures where atmospheric pressure is lower. Boiling point rises with the strength of intermolecular forces, making it a sensitive indicator of hydrogen bonding and molecular size.
Examples in the real world
Water boils at 100 °C at sea level but near 70 °C on Everest; a pressure cooker raises it to about 120 °C.