Types of Reactions
Year 8 ⚗️ Chemical Reactions Classify reactions as synthesis, decomposition, combustion or displacement.
⚗️ Reaction Types
Chemical reactions are classified by the pattern of reactants and products.
| Type | Pattern | Example |
|---|---|---|
| Synthesis | A + B → AB | 2Mg + O₂ → 2MgO |
| Decomposition | AB → A + B | CaCO₃ → CaO + CO₂ |
| Displacement | A + BC → AC + B | Fe + CuSO₄ → FeSO₄ + Cu |
| Neutralisation | acid + base → salt + water | HCl + NaOH → NaCl + H₂O |
| Combustion | fuel + O₂ → CO₂ + H₂O | CH₄ + 2O₂ → CO₂ + 2H₂O |
| Precipitation | 2 solutions → insoluble solid | BaCl₂ + Na₂SO₄ → BaSO₄↓ + 2NaCl |
🔥 Combustion
Combustion is the rapid reaction of a fuel with oxygen. Complete combustion produces CO₂ and H₂O; incomplete combustion produces CO (toxic) and/or soot.
Carbon monoxide (CO) is odourless and toxic — produced by incomplete combustion in poorly ventilated spaces.
🌡️ Exothermic & Endothermic
Reactions that release energy are exothermic (temperature rises); reactions that absorb energy are endothermic (temperature falls).
Exothermic: combustion, neutralisation, oxidation/rusting.
Endothermic: thermal decomposition, dissolving NH₄NO₃, photosynthesis.
Endothermic: thermal decomposition, dissolving NH₄NO₃, photosynthesis.
Ready to test yourself? Click the Quiz tab above to practise questions on this topic!
Interactive Demonstration — Types of Reactions
Identify the type of each chemical reaction.
Click to identify the reaction type.
⚗️ Reaction Type Classifier
Calculate the atom economy of a reaction.