Why does lowering the pressure cause a liquid to boil

This pressure is transmitted throughout the liquid and makes it more difficult for bubbles to form and for boiling to take place. If the pressure is reduced, the liquid requires less energy to change to a gaseous phase, and boiling occurs at a lower temperature

Explanation:

Atmospheric Pressure and Boiling

The pressure of gas above a liquid affects the boiling point. ... If the pressure is reduced, the liquid requires less energy to change to a gaseous phase, and boiling occurs at a lower temperature

in the analysis of systems that involve fluid flow, we frequently encounter the combination of properties u and pv.