Which term describes the temperature at which a substance can spontaneously ignite in air?

The term that describes the temperature at which a substance can spontaneously ignite in air is known as the autoignition temperature (AIT). At this specific temperature, the substance can ignite without the need for an external spark or flame. This characteristic is crucial for safety in industries that handle flammable materials, as knowing the AIT helps in assessing the fire risk and implementing appropriate safety measures to prevent unintentional ignition.

In contrast, the flash point refers to the lowest temperature at which a liquid can produce enough vapor to form an ignitable mixture with air. This is not the same as the AIT, which indicates spontaneous ignition rather than just the formation of an ignitable mixture. Burning velocity relates to how quickly a flame propagates through a combustible gas mixture and is more about the combustion characteristics rather than ignition temperatures. The vaporization point is the temperature at which a substance turns from a liquid to a gas, playing a role in determining the potential for producing flammable vapors but not directly related to spontaneous ignition. Understanding the distinct definitions and implications of these terms helps in assessing and managing explosion hazards effectively.