Knowledge Organiser: Endothermic Reactions
Part of Endothermic Reactions · GCSE GCSE Chemistry revision
This topic summary covers Knowledge Organiser: 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 12 of 12 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 12 of 12
Practice
20 questions
Recall
14 flashcards
Knowledge Organiser: Endothermic Reactions
Key Terms
- Endothermic — absorbs energy from surroundings
- ΔH — enthalpy (energy change) — positive for endothermic
- Thermal decomposition — breakdown by heat
- Photosynthesis — key endothermic example
- Reversible reaction — reverse has opposite ΔH sign
Must-Know Facts
- Temperature of surroundings DECREASES
- Products have MORE energy than reactants
- ΔH is POSITIVE
- Products are HIGHER on energy profile
- Examples: photosynthesis, thermal decomposition
- Energy needed breaking bonds > energy released making bonds
Key Equations
- ΔH = energy required breaking bonds − energy released making bonds
- Endothermic: ΔH is positive (energy absorbed from surroundings)
- Reversible reaction: if forward is endothermic, reverse is exothermic by same ΔH
Common Mistakes
- Saying endothermic reactions release heat: Endothermic reactions ABSORB energy from surroundings — the temperature of the surroundings decreases
- Getting products position wrong on energy profile: For endothermic, products are HIGHER than reactants on the y-axis — draw the profile arrow going UP at the end
- Forgetting cooling packs are endothermic: Endothermic reactions feel cold — hand warmers are exothermic; cooling packs (sports injuries) are endothermic
- Saying reversible reactions have no energy change: The reverse reaction has the OPPOSITE energy change — if forward is endothermic (+x kJ), reverse is exothermic (−x kJ)
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Practice Questions for Endothermic Reactions
In an endothermic reaction, energy is:
Explain why a sports cold pack becomes cold when activated.
Quick Recall Flashcards
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