What process must liquid fuels undergo to ignite?

Liquid fuels must undergo the process of vaporization to ignite because ignition occurs when a fuel's vapors mix with an adequate amount of oxygen and come into contact with a heat source. Vapors are the gaseous form of the fuel that arise when the liquid is heated or agitated, allowing it to transform into a flammable vapor. This conversion is critical because most liquid fuels do not ignite in their liquid state; instead, they require vaporization to produce a mixture capable of sustaining combustion.

In the context of combustion, it is the vapor phase of the fuel that reacts with oxygen, leading to a fire. While pyrolysis refers to the thermal decomposition of materials at elevated temperatures in the absence of oxygen, and evaporation is a process where liquid turns to gas typically at lower temperatures without combustion involved, they do not directly describe the specific phase change necessary for ignition in liquid fuels. Therefore, vaporization is the essential step for liquid fuels to ignite, as it prepares them to form the combustible mixture needed for combustion to occur.