Of Gunpowder, Treason and Plot.. well maybe not the last two...

Gunpowder is an ancient Chinese invention, reported to have been first created during the Song dynasty while alchemists (there were no chemists then) were trying to find an elixir of immortality. We highly doubt that gunpowder was able to serve this purpose.

Gunpowder is flammable and explosive, due to the ingredients present in its 'recipe'. Original gunpowder was made from charcoal bits, sulphur and saltpeter. This combination of ingredients creates what is known as a 'self-oxidising fuel', due to the presence of potassium nitrate (KNO3) in the saltpeter. Once ignited the carbon in the charcoal combusts very rapidly, as the nitrate in the saltpeter decomposes to give nitrogen, its oxides, and oxygen, which increase the rate of combustion. At the same time sulphur reduces the temperature needed for ignition, which helps initiate the reaction and raises the combustion rate as well. The end result is a potent mix of solid powders that burn rapidly, creating large amounts of heat and smoke.

As such, gunpowder is used as a propellant, making rockets fly and bullets zip.

In this activity we will explore the science behind the synthesis of gunpowder.
Original-grade gunpowder is first made using the following laboratory chemicals:

Carbon powder 0.15 g
Potassium nitrate 0.75 g
Sulphur 0.10 g

for a mixture totaling 1.0 grams. It is not advised to synthesise more than this amount as a large amount of gunpowder will produce too much thermal energy for lab apparatus to cope with safely. At the same time, larger amounts of gunpowder increase the risk of violent explosion if ignited all at once.

The above chemicals are weighed out and mixed together in a crucible. A glass rod is used to break up any large particles in the mixture to ensure an even distribution of all ingredients. Once mixed properly, the crucible containing the gunpowder mixture is placed in a glass basin, or on an asbestos tile, in a well-ventilated area clear of any flammable materials and ignited by means of a match, and the resulting combustion is observed.

After this, a stronger oxidising agent can be substituted in place of potassium nitrate to alter the rate and intensity of combustion. In this experiment potassium chlorate (V), KClO3, is used. As it is a very strong oxidising agent, ignition is now carried out using a long burning splint to avoid burns.