Unit 9H Lesson 3: Combustion Objectives: to learn about efficient combustion, to learn how explosives work, and to learn about the dangers of poisonous gas created by combustion.

The Fire Triangle In order for a fire to burn three things are required: Oxygen Heat Fuel If any one of these things are removed the fire will stop burning.

The Combustion Reaction Most of the fuels we use are compounds which have carbon in them. –Methane or CH 4 is a good example. If there is a complete burn of all the fuel in the reaction the word formula for the reaction will look like this: –Fuel + Oxygen  Carbon Dioxide + Water If the fuel is not completely burned the reaction will look like this: –Fuel + Oxygen  Soot + Carbon Dioxide + Water –The soot is actually just unburned carbon. See figure one page 98.

Carbon Monoxide Sometimes when things burn a poisonous gas called carbon monoxide is released. Carbon monoxide bonds with our red blood cells preventing them from carrying oxygen. If we inhale carbon monoxide it will eventually kill us.

Explosions An explosion occurs when a substance burns very very quickly. When an explosion occurs there is a sudden and violent release of energy. Explosives can burn instantly because the chemicals they are made of have a fuel and oxygen built into them. –Because of this they don’t have to rely on the air to provide oxygen.

Gunpowder and Matches Gunpowder is an explosive which consists of: –Charcoal (fuel) –Sulphur (fuel) –Saltpetre (potassium nitrate which contains lots of oxygen atoms) A match is an explosive which contains: –Carbon (fuel) –Sulphur (fuel) –Potassium Chlorate (provides the oxygen)

Work to Do Complete questions 1-12 page 99 Homework –Complete H/W sheet 8.2 –Define the keywords: Combustion, unburned, explosive, gunpowder, methane, saltpetre