Page 37 - Curriculum Visions Dynamic Book

Spontaneous combustion
Spontaneous combustion can be due to combining an oxidising agent with another substance as shown on these pages. Matches are a chemical reaction between the chemicals of the match head and the box side. The result is rapid oxidation and the generation of enough heat to catch the match wood alight.
Spontaneous combustion can also occur when, for example, a strong light is focused by a piece of glass. This will cause the temperature of a sheet of paper to rise enough for rapid oxidation (burning) to occur. It shows clearly that a flame is not needed to set something alight.
Some people find out that microwaves can also cause combustion. If the timer on a microwave oven is set too long, the food may get hot enough to catch fire.
Spontaneous combustion can occur in any place where there is poor circulation of air around a fuel. For example, dried grass in a haystack will oxidise, releasing heat. If there is enough air to allow continued oxidation, but
not enough to carry away the heat, then a temperature may be reached when combustion occurs. Piles of oily rags and coal have all been known to burst into flame spontaneously.
Spontaneous combustion is also possible with any dusty fuel, because the greater surface area of the dust means that it can oxidise more easily. This is why coal dust explodes in mines and why even flour dust in a flour mill sometimes catches fire.
exothermic reaction: a reaction that gives heat to the surroundings. Many oxidation reactions, for example, give out heat.
induction period: the time that sometimes elapses between
the start of a chemical reaction and when that reaction actually becomes obvious. For example,
a fabric might begin to smoulder imperceptibly if heated and
then, sometime later, burst into flames without any apparent cause. Chemical reactions can be extremely dangerous if people are unaware of the induction period involved.
spontaneous combustion: the effect of a very reactive material beginning to oxidise very quickly and bursting into flame.
 The potassium permanganate and ethylene glycol have produced enough heat to make a miniature “volcano” in the laboratory.
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