What's covered
Key facts
Combustion
Carbon monoxide is a colourless, odourless, toxic gas; it binds to haemoglobin in red blood cells more strongly than oxygen, preventing oxygen transport.
Chemical reactions and equations
Methane combustion: methane + oxygen → carbon dioxide + water (CH₄ + 2O₂ → CO₂ + 2H₂O).
Oxidation and reduction
Carbon acts as a reducing agent when used to extract metals from metal oxides; carbon is oxidised to carbon dioxide while the metal oxide is reduced to the metal.
Combustion
Combustion is an exothermic reaction between a fuel and oxygen that releases thermal energy and light.
Oxidation and reduction
Combustion is an oxidation reaction — the fuel gains oxygen; the word equation for burning carbon: carbon + oxygen → carbon dioxide.
Combustion
Complete combustion (plenty of oxygen): hydrocarbon fuel + oxygen → carbon dioxide + water.
Oxidation and reduction
Extracting a metal from its ore (metal oxide) involves reduction — the metal oxide loses oxygen; e.g. copper oxide + carbon → copper + carbon dioxide.
Combustion
Combustion requires three things: fuel, oxygen, and heat (ignition temperature); removing any one of these extinguishes the fire — this is the basis of fire-fighting.
Oxidation and reduction
At KS3, oxidation is defined as the gain of oxygen by a substance during a chemical reaction.
Combustion
Burning fossil fuels (coal, oil, natural gas) releases CO₂ stored over millions of years into the atmosphere, contributing to the enhanced greenhouse effect and climate change.
Sample questions
A taste of the 57 questions in this topic, answers marked. Sign up to practise the full set with spaced repetition.
What is the pH range of acids?
- •Above 14
- •Above 7
- ✓Below 7
- •Exactly 7
What is a chemical reaction?
- •Liquids change state only
- •Particles split into atoms
- ✓Reactants change into new products
- •Same substances move around
What is combustion?
- ✓Burning a fuel in oxygen, releasing energy
- •Cooling a hot fuel down by half temperature
- •Iron rusting slowly in damp air outdoors
- •Salt dissolving steadily in warm water
What is an exothermic reaction?
- •A reaction at high pressure
- •A reaction that absorbs energy
- ✓A reaction that releases energy
- •A reaction without any products
At KS3, what is oxidation defined as?
- ✓The gain of oxygen by a substance
- •The gain of water by a substance
- •The loss of heat by a substance
- •The loss of oxygen by a substance
Which is the most reactive metal in the list?
- •Copper metal
- •Gold metal
- •Iron metal
- ✓Potassium
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