Final answer:
The range of concentrations at which a vapor-to-fuel mixture can ignite is called the flammability range, encompassing both the lower explosive limit and upper explosive limit. Temperature, density, and time are factors that influence whether the mixture reaches ignition.
Step-by-step explanation:
The span of concentrations at which a vapor-to-fuel mixture in the air is capable of burning is referred to as the flammability range or explosive limit.
This range is crucial for safety in chemical handling and processes. The flammability range includes the minimum concentration of vapor, known as the lower explosive limit (LEL), below which the mixture is too lean to burn, and the maximum concentration, known as the upper explosive limit (UEL), above which the mixture is too rich to ignite.
Factors such as temperature, density, and time affect the ignitability of the mixture, complementing one another; a deficiency in one can sometimes be compensated for by the excess of another.
It's important to note that reaching ignition is a pivotal step towards the development of commercial combustion plants, as this defines the point at which a fuel mixture can sustain burning without external energy input.
This concept also applies to internal combustion engines, where the mixture ignites, leading to an increase in pressure and temperature as described by the ideal gas law (PV = NkBT), resulting in the engine performing work.