What is the relationship of vapor pressure to temperature of a liquid? As temperature increases, vapor pressure increases. Vapor pressure is not dependent on temperature. As temperature increases, vapor pressure decreases. The relationship depends on the polarity of the liquid. Question 3 Which substance would you expect to have the highest vapor pressure at 25C ? Water has a higher boiling point than ethanol (CH3CH2OH). At any given temperature, would you expect the vapor pressure of water to be higher or lower than that of ethanol? Higher Lower