Page 41 - Curriculum Visions Dynamic Book

explosive: a substance which, when a shock is applied to it, decomposes very rapidly, releasing a very large amount of heat and creating a large volume of gas as a shock wave.
high explosive: a form of explosive that will only work when it receives a shock from another explosive. High explosives are much more powerful than ordinary explosives. Gunpowder is not a high explosive.
poison gas: a form of gas that is used intentionally to produce widespread injury and death. (Many gases are poisonous, which is why many chemical reactions are performed in laboratory fume chambers, but they are a byproduct of a reaction and not intended to cause harm.)
Gunpowder
Gunpowder is the best known and earliest form of explosive. It is made by mixing powders of sulphur, charcoal and saltpetre (potassium nitrate) together. The first people to invent gunpowder were the Chinese, and gunpowder has been in use for nearly one thousand years.
Gunpowder is ignited by means of a spark (say from tinder in a flintlock rifle), a flame (light the fuse and stand clear, as in fireworks) or an electric arc (as in detonation with an electrical plunger).
When gunpowder was first made, it was mixed and then crushed into a powder by people using hammers. As a result, from time to time, the shock of the hammers caused the powder to explode. Making gunpowder was never a good trade to be in!
The modern manufacture of gunpowder – now called black powder – is by pulverising charcoal with sulphur and then mixing it with potassium nitrate so that the particles of nitrate, sulphur and charcoal all come into close contact. To do this, very heavy steel wheels are rolled over a black powder mixture spread on a steel plate. The mixture is then pressed into a cake and broken down into granules.
The main modern use of gunpowder is in fireworks. For this purpose the gunpowder is mixed with graphite, which coats the powder and makes it less likely to explode as it is carried about. Elsewhere, black powder is used as a first charge to set off artillery shells and other munitions.
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