Which property of a liquid indicates its tendency to form vapors?

Vapor pressure is a crucial property of liquids that indicates their tendency to evaporate or form vapors at a given temperature. It is essentially a measure of the pressure exerted by a vapor in equilibrium with its liquid (or solid) phase. The higher the vapor pressure of a liquid at a specific temperature, the more likely it is to produce vapor, as it indicates a greater number of molecules are escaping from the liquid phase into the vapor phase.

Understanding vapor pressure is important in fire-related contexts because it helps to assess how easily a liquid can ignite, given that flammable liquids with higher vapor pressures can release vapors that may result in explosive or hazardous situations, especially in confined or poorly ventilated spaces.

Other properties listed, such as specific gravity, provide information about the density of a liquid compared to water but do not directly relate to its vapor formation. The freezing point indicates the temperature at which a liquid becomes solid and does not provide insight into vaporization tendencies. The flash point is the lowest temperature at which a liquid can produce enough vapor to ignite but does not measure the actual vapor pressure itself. Thus, vapor pressure is the specific attribute that directly correlates to the tendency of a liquid to vaporize.