ACS Chemistry Practice Exam 2025 – The All-in-One Guide to Exam Success!

Vapor pressure is fundamentally influenced by temperature because it is a measure of the tendency of a liquid to evaporate. As the temperature increases, the kinetic energy of the molecules in the liquid also increases. This higher kinetic energy allows more molecules to overcome intermolecular forces and transition into the gas phase, thereby increasing the vapor pressure.

At elevated temperatures, more molecules have sufficient energy to escape into the vapor phase, resulting in a greater concentration of vapor above the liquid, which corresponds to a higher vapor pressure. Conversely, at lower temperatures, the kinetic energy of the molecules decreases, leading to a lower vapor pressure since fewer molecules can transition to the gas phase.

Other factors like initial volume, concentration, and density might have indirect effects on the system, but they do not fundamentally determine the vapor pressure of a liquid. Initial volume or concentration could alter the amount of liquid present but do not change the inherent property of the liquid's vapor pressure. Density relates to mass per unit volume and also does not directly impact the vapor pressure as temperature does. Thus, temperature is the primary factor affecting vapor pressure in liquids.