Autoignition temperature is the temperature to which a substance must be heated for ignition and self-sustained combustion to occur without an external heat source.

Autoignition temperature is the temperature to which a substance must be heated for ignition and self-sustained combustion to occur without an external heat source.

• A. The temperature to which a substance must be heated for ignition and self sustained combustion to occur without an external heat source
• B. The temperature at which the substance will ignite with a flame
• C. The temperature at which the substance melts
• D. The temperature at which a spark ignites a volatile vapor

Answer: (A)

Autoignition temperature is the threshold at which a material will ignite and sustain combustion in air without any external heat source such as a flame or spark. At this temperature, the heat generated by the material’s own oxidation exceeds the heat lost to the surroundings, causing spontaneous ignition. The statement here matches that definition exactly: ignition occurs self-sustainably once that temperature is reached, without an outside heat source. This concept differs from other heat-related properties. Ignition with a flame relies on an external ignition source, which is not autoignition. Melting is a phase change from solid to liquid, not related to ignition. Ignition from a spark also requires an outside ignition source rather than occurring spontaneously.

Autoignition temperature is the threshold at which a material will ignite and sustain combustion in air without any external heat source such as a flame or spark. At this temperature, the heat generated by the material’s own oxidation exceeds the heat lost to the surroundings, causing spontaneous ignition. The statement here matches that definition exactly: ignition occurs self-sustainably once that temperature is reached, without an outside heat source.

This concept differs from other heat-related properties. Ignition with a flame relies on an external ignition source, which is not autoignition. Melting is a phase change from solid to liquid, not related to ignition. Ignition from a spark also requires an outside ignition source rather than occurring spontaneously.