Final answer:
Volatility is the characteristic that refers to how easily a liquid changes into a vapor state, which is governed by the substance's vapor pressure at a given temperature.
Step-by-step explanation:
The characteristic that refers to how easily a liquid changes into a vapor state is known as volatility. Volatility is a measure of a substance's tendency to vaporize. It depends on the substance's vapor pressure at a given temperature, which is the pressure exerted by the vapor when the liquid and vapor are in dynamic equilibrium in a closed system. Volatile liquids, such as diethyl ether and acetone, have high vapor pressures and evaporate readily at room temperature. Conversely, nonvolatile liquids, like motor oil, have low vapor pressures and evaporate much more slowly.
The term "evaporation" refers to the conversion of a liquid to its vapor below the boiling temperature, while "boiling point" is the temperature at which the vapor pressure of the liquid is equal to the external pressure, causing the liquid to boil. However, volatility is the proper term when discussing the ease of transitioning from liquid to vapor under conditions not limited to boiling.