What does vapor pressure measure?

Vapor pressure is a measure of the tendency of a liquid to evaporate. It quantifies the pressure exerted by the vapor of a substance in equilibrium with its liquid phase at a given temperature. When a liquid evaporates, molecules at the surface escape into the gas phase, contributing to the vapor pressure. A high vapor pressure indicates that a liquid readily evaporates at room temperature, while a low vapor pressure suggests that the liquid does not evaporate easily. Understanding vapor pressure is essential in hazardous materials management because it helps predict how a substance will behave in various conditions, such as spills or leaks, and informs decision-making about containment and response measures.

The other options do not relate directly to the concept of vapor pressure: freezing refers to the solidification of a liquid, dissolving pertains to the ability of a substance to mix with a solvent, and conducting electricity describes the property of materials to allow the flow of electric current, none of which are connected to the evaporation process measured by vapor pressure.