Which of the following contributes to the higher volatility of JP-4 compared to other fuels?

The higher volatility of JP-4 compared to other fuels is primarily attributed to its lower boiling point. Volatility refers to how readily a substance vaporizes; a lower boiling point indicates that the fuel can transition from liquid to vapor at lower temperatures, making it more volatile. JP-4, being a blend of hydrocarbons, contains lighter fractions which allows it to evaporate more easily than fuels with higher boiling points.

This characteristic is crucial for aviation fuels, as it ensures that the fuel can vaporize efficiently and form a flammable mixture with air in the engine. The lower boiling point facilitates quick start-up and optimal combustion performance, particularly in aviation applications where temperature variations can be significant.

In contrast, the other options do not contribute to increased volatility. A higher molecular weight typically results in heavier, less volatile fuels. Increased density may imply a greater mass per unit volume but does not necessarily correlate with volatility. Lastly, reduced vapor pressure would indicate less tendency to vaporize, further supporting the reasoning that lower boiling points are what enhance a fuel's volatility, particularly in the context of comparing JP-4 with other fuels.