What term describes gasoline's ability to transition into vapor?

Volatility is the term used to describe gasoline's ability to transition into vapor. This characteristic is crucial in understanding how fuels behave under different conditions. Gasoline is designed to evaporate easily, which is essential for the efficient functioning of internal combustion engines. The more volatile a substance is, the more readily it converts from liquid to vapor at a given temperature and pressure. This property affects fuel performance, as it facilitates the mixing of gasoline with air to create a combustible mixture necessary for combustion in engines.

The other options do not accurately describe this process. Density refers to the mass of a substance per unit volume, which influences how heavy a liquid feels but does not directly relate to its ability to vaporize. Viscosity measures a fluid's resistance to flow, which is important in understanding how it moves but is not a factor in how easily gasoline vaporizes. Reactivity involves how a substance reacts chemically with other substances, which is relevant to combustion but does not specifically address the vaporization process. Thus, volatility specifically defines the ease with which gasoline can transition from a liquid to a vapor state.