What does 'boiling point elevation' describe?

Boiling point elevation describes how the boiling point of a solvent increases when a non-volatile solute is added. This phenomenon occurs due to the disruption of the solvent's molecular interactions, which requires more energy (in the form of heat) to reach the boiling point. When a solute is introduced, it takes up space in the solution and reduces the number of solvent molecules that can escape into the vapor phase, thereby elevating the temperature at which the boiling point is reached. This principle is a colligative property, meaning it depends on the number of solute particles in a solution rather than their nature.

The other choices relate to different physical effects that do not explain boiling point elevation. For example, the first option discusses how boiling points can decrease under increased pressure, which is the opposite of elevation. The third option deals with how altitude affects boiling time due to reduced atmospheric pressure, impacting the boiling point but not in the context of solute addition. The fourth option addresses the relationship between temperature and vapor pressure, which is a separate concept involving changes in the state of the substance rather than the impact of solutes.