Why does petrol catch fire
so soon while wood takes comparatively longer?
Every object catches fire, that is, it combines with the oxygen in the air, emitting heat and light, at a specific temperature. This temperature is known as the ignition point or ignition temperature of that object.
Different materials have different ignition points. Petrol catches fire quickly because it has a low ignition point; wood has a higher ignition point.
A substance does not have to be touched by flame to begin burning. It simply needs to be heated above its ignition point.
In a
burning building for example, heat and not flame is the greatest cause of fire
spread. Metallic objects are the most frequent conductors of heat. Often heat from
one room that is on fire is conducted to another by water or gas pipes. If
combustible matter is in contact with the pipe it can become heated above its ignition
point and start a second fire. Sometimes even brick walls can conduct enough
heat to cause a second fire.
