What is true of the vapor pressures of a substance at 38° C (100° F) compared to the same substance at 20° C (68° F)?

The correct understanding is that the vapor pressure of a substance increases with an increase in temperature. At 38° C (100° F), the molecules of a substance have higher kinetic energy compared to the same substance at 20° C (68° F). As temperature rises, more molecules have sufficient energy to escape the liquid phase and enter the vapor phase, resulting in a higher vapor pressure.

This phenomenon occurs because higher temperatures provide molecules with more energy to overcome intermolecular forces, allowing a greater number of molecules to enter the gas phase. Consequently, at 38° C, the vapor pressure will indeed be higher than at 20° C, reflecting the increased energy and activity of the molecules at the elevated temperature.