What happens to vapor pressure as temperature increases?

• A. Increases
• B. Decreases
• C. Remains the same
• D. Becomes negligible

Answer: (A)

Vapor pressure increases with temperature. Vapor pressure is the pressure exerted by the vapor in equilibrium with the liquid. When you heat a liquid, more molecules gain enough energy to break free from the surface into the vapor phase, so the amount of vapor—and thus the pressure it exerts—rises. The system shifts to a new equilibrium with a higher saturation vapor pressure as temperature climbs. When vapor pressure reaches the surrounding pressure, boiling can occur. In hazmat contexts, higher vapor pressure at elevated temperatures means more vapors can be generated and dispersed, increasing inhalation and ignition hazards. So the behavior is a rise in vapor pressure as temperature increases.