A liquid boils when its
A) vapor pressure is exactly 1 atmosphere.
B) vapor pressure is equal to or greater than the external pressure.
C) temperature is equal to 273 K (standard temperature).
D) temperature is greater than room temperature.
E) thermal energy is equal to the heat of vaporization.

Question

Quizplus · Accepted Answer

A liquid boils when its vapor pressure is equal to or greater than the external pressure. This is because the vapor pressure is a measure of the tendency of molecules to escape from the liquid and become a gas. When the vapor pressure is equal to or greater than the external pressure, the molecules can escape freely and a gas or vapor is formed.

A Liquid Boils When Its