How does pressure affect boiling points of substances?

Pressure significantly affects the boiling points of substances because boiling occurs when a liquid's vapor pressure equals the surrounding atmospheric pressure. At higher pressures, more energy is required for the vapor pressure to reach that point, resulting in a higher boiling point. Conversely, at lower pressures, such as at high altitudes, liquids boil at lower temperatures since the atmospheric pressure is reduced. This relationship is described by the Clausius-Clapeyron equation, which illustrates how changes in pressure influence phase transitions.