The MINIMUM temperature at which a liquid fuel gives off sufficient vapors to form an ignitable mixture with air near its surface is best described as:

• A. Flash point
• B. Autoignition temperature
• C. Boiling point
• D. Melting point

Answer: (A)

The flash point is the minimum temperature at which a liquid fuel releases enough vapor to form an ignitable mixture with air at the surface, so that an ignition source can ignite those vapors. Below this temperature, there aren't enough vapors to support ignition; above it, a spark or flame can start combustion. This is distinct from the autoignition temperature, which is the temperature at which the vapor will ignite without any flame or spark, and from the boiling point, which is when the liquid turns to vapor as a whole. The melting point is simply the temperature at which a solid becomes a liquid. So the description matches the flash point.