Exam Tips for Endothermic Reactions
Part of Endothermic Reactions — GCSE Chemistry
This exam tips covers Exam Tips for Endothermic Reactions 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 regularly enough that it should still be part of a steady revision cycle. It is section 11 of 12 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Topic position
Section 11 of 12
Practice
20 questions
Recall
14 flashcards
💡 Exam Tips for Endothermic Reactions
🎯 Common Question Types:
- "Explain why this reaction is endothermic" (2 marks)
- "Draw an energy profile for an endothermic reaction" (2 marks)
- "The forward reaction is endothermic — what can you say about the reverse?" (1-2 marks)
- "Is photosynthesis exothermic or endothermic? Explain." (2 marks)
📝 Key Command Words:
- Explain — state the energy direction (from surroundings to chemicals) and the effect (temperature falls)
- Draw — label axes, show products ABOVE reactants, include activation energy peak
- Suggest — use your knowledge to propose an explanation for unfamiliar data
⚠️ Common Mistakes to Avoid:
- Drawing the energy profile with products BELOW reactants (that's exothermic!)
- Using negative ΔH for endothermic — endothermic ΔH is always POSITIVE
- Saying "endothermic means no energy is released" — energy is both absorbed AND released in every reaction; endothermic means more is absorbed than released overall
- Forgetting that photosynthesis is the most important endothermic reaction to know
Quick Check: Give TWO examples of endothermic reactions and explain how you know they are endothermic.
1. Photosynthesis — plants absorb light energy from the sun to convert CO₂ and water into glucose. Energy is taken IN from the surroundings (sunlight), so it is endothermic. 2. Thermal decomposition of calcium carbonate — CaCO₃ → CaO + CO₂. Continuous heating is required to make this reaction happen, meaning energy must be continuously absorbed from the surroundings. ΔH is positive for both reactions.