CIE iGCSE Co-Ordinated Science C6.1 Physical and chemical changes Exam Style Questions Paper 1
▶️ Answer/Explanation
Combustion of alkanes is a chemical change because new substances (carbon dioxide and water) are formed and energy is released. Boiling water is a physical change (state change only). Filtering is a physical separation technique, and fractional distillation separates mixtures without forming new substances.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
Combustion of hydrocarbons is a chemical change because new substances (\(\text{CO}_2\) and \(\text{H}_2\text{O}\)) are formed and the reaction is not easily reversible.
Options B, C, and D are all physical changes — no new substances are formed, and the changes are reversible (e.g. freezing water is the reverse of melting).
✅ Answer: (A)
Options B, C, and D are all physical changes — no new substances are formed, and the changes are reversible (e.g. freezing water is the reverse of melting).
✅ Answer: (A)
▶️ Answer/Explanation
Any reaction with a final temperature above 21 °C is exothermic (heat is released to the surroundings), and any reaction with a final temperature below 21 °C is endothermic (heat is absorbed from the surroundings).
By comparing each reaction’s final temperature to the initial 21 °C, the reactions can be correctly classified as exothermic or endothermic — row B correctly assigns all four reactions based on their temperature changes.
✅ Answer: (B)
By comparing each reaction’s final temperature to the initial 21 °C, the reactions can be correctly classified as exothermic or endothermic — row B correctly assigns all four reactions based on their temperature changes.
✅ Answer: (B)
▶️ Answer/Explanation
Burning a wooden splint converts the wood into new substances such as carbon dioxide, water and ash — a chemical change.
Dissolving, evaporating and distilling are all physical changes because no new substance is formed and the change is reversible.
Only burning permanently produces different chemical substances, so it is the chemical change.
✅ Answer: (A)
Dissolving, evaporating and distilling are all physical changes because no new substance is formed and the change is reversible.
Only burning permanently produces different chemical substances, so it is the chemical change.
✅ Answer: (A)
▶️ Answer/Explanation
Limestone is calcium carbonate, \(CaCO_3\).
Heating breaks it down into calcium oxide (lime) and carbon dioxide.
Breaking down one compound into simpler substances using heat is thermal decomposition.
✅ Answer: (D)
Heating breaks it down into calcium oxide (lime) and carbon dioxide.
Breaking down one compound into simpler substances using heat is thermal decomposition.
✅ Answer: (D)