Final answer:
Intermolecular forces determine the ease with which molecules escape the liquid state to become gas, thus affecting vapor pressure and boiling point. Substances with stronger intermolecular forces have lower vapor pressure and higher boiling points, while increasing temperature raises vapor pressure until it equals external pressure, resulting in boiling.
Step-by-step explanation:
The relationship between intermolecular forces, vapor pressure, and boiling point is a central concept in understanding the physical properties of substances. Intermolecular forces are attractions between molecules that determine the physical state and properties of a substance. When a liquid's molecules have enough thermal energy to overcome these forces, they can escape the liquid phase and enter the gas phase, a process known as vaporization.
Vapor pressure is the pressure exerted by the vapor above a liquid and represents how many molecules have vaporized. It is directly affected by the strength of intermolecular forces; stronger forces result in fewer molecules escaping and a lower vapor pressure, while weaker forces result in a higher vapor pressure. Temperature also affects vapor pressure; as temperature increases, more molecules have enough energy to escape, and vapor pressure rises.
The boiling point of a substance is the temperature at which its vapor pressure equals the external pressure. Substances with stronger intermolecular forces require higher temperatures to achieve the same vapor pressure and therefore have higher boiling points. At high altitudes, boiling points are lower because the atmospheric pressure is reduced, allowing substances to boil at lower temperatures.