This exam focus covers Exam Focus within Endothermic Reactions for GCSE Chemistry. Revise Endothermic Reactions in Energy Changes for GCSE Chemistry with 20 exam-style questions and 14 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 10 of 12 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
🎯 Exam Focus
Frequently Examined
Endothermic reactions are often tested alongside exothermic reactions in compare-and-contrast questions. Key areas:
- Comparing ΔH signs — positive for endothermic, negative for exothermic
- Drawing/interpreting energy profiles — products higher for endothermic
- Reversible reactions — if forward is endothermic, reverse is exothermic
- Photosynthesis and thermal decomposition — most commonly cited examples
- Identifying from experimental data — temperature DROPS → endothermic
Edexcel 1CH0: Examined in Paper 2 (1CH0/2). Edexcel tests the difference between exothermic and endothermic reactions using temperature change data. In Edexcel-style questions, the command word "Suggest" appears frequently — use your chemistry knowledge to apply to an unfamiliar context.
Quick Check: The decomposition of calcium carbonate is endothermic: CaCO₃ → CaO + CO₂. What would be the sign of ΔH for the REVERSE reaction (CaO + CO₂ → CaCO₃)?
The reverse reaction would be EXOTHERMIC, so ΔH would be NEGATIVE. When a reaction is reversed, the energy change is equal in magnitude but opposite in sign. If the forward reaction absorbs energy (+ΔH), the reverse reaction releases the same amount of energy (−ΔH).
Practice questions for Endothermic Reactions
In an endothermic reaction, energy is:
Explain why a sports cold pack becomes cold when activated.