What is the effect of pressure on a liquid's boiling point?

The boiling point of a liquid is the temperature at which its vapor pressure equals the external pressure surrounding the liquid. At this temperature, the liquid transitions to a gas. For example, water boils at 100°C at standard atmospheric pressure (1 atm), but this temperature changes with variations in pressure.

Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid or solid form at a given temperature. As temperature increases, the vapor pressure of a liquid also increases, leading to a higher likelihood of molecules escaping into the gas phase. This relationship is crucial for understanding how boiling points change with pressure.

Increasing the external pressure on a liquid raises its boiling point because the liquid must reach a higher temperature for its vapor pressure to match the increased external pressure. Conversely, reducing the pressure lowers the boiling point, which is why water boils at lower temperatures at high altitudes, where atmospheric pressure is lower.