Lowering the atmospheric pressure on a liquid

The boiling point of a liquid is defined as the temperature at which its vapor pressure equals the external atmospheric or ambient pressure [2]. Atmospheric pressure acts as a resistive force, pushing down on the liquid's surface and making it difficult for molecules to escape and form bubbles [1]. When the atmospheric pressure is lowered, such as at high altitudes, the liquid molecules meet less resistance from air molecules and can enter the gaseous phase more easily [2]. Consequently, the vapor pressure matches the external pressure at a lower temperature, thereby lowering the boiling point [2]. Conversely, increasing the pressure requires more energy for the liquid to boil, which raises the boiling point [1]. Therefore, reducing the pressure directly results in a decrease in the temperature required for boiling to occur [2].

Sources

1. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > Vertical Variation of Atmospheric Pressure > p. 305
2. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 3: Geological Time Scale The Evolution of The Earths Surface > 3. Geological Time Scale – The Evolution of The Earth's Surface > p. 43