What does the boiling point of a substance represent in terms of vapor pressure?

The boiling point of a substance represents the temperature at which the vapor pressure of that substance equals the atmospheric pressure. At this point, the energy provided by the heat is sufficient for the molecules of the liquid to overcome intermolecular forces and enter the gaseous state. This equilibrium between vapor pressure and atmospheric pressure means that bubbles of vapor can form within the liquid, allowing it to boil.

In practical terms, as a liquid is heated, its vapor pressure increases. When the vapor pressure reaches the pressure exerted by the surrounding atmosphere, boiling occurs. This relationship is fundamental in understanding how boiling points can change with variations in external pressure, such as at high altitudes where atmospheric pressure is lower, resulting in lower boiling points.