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Paper 1
Energy Changes
Both
Exothermic reactions release energy; endothermic absorb energy.
Key Facts
- Reaction profiles show energy change and activation energy.
- Catalysts lower activation energy.
Topics Covered
Exothermic vs Endothermic
What you need to know
- •Exothermic reactions release energy to the surroundings.
- •Endothermic reactions take in energy.
Exam Tips
- Use temperature change to identify the type.
Bond Energies
What you need to know
- •Breaking bonds absorbs energy.
- •Making bonds releases energy.
Exam Tips
- Energy change = energy to break - energy to make.
Key Terms
Activation energy
Minimum energy needed for a reaction to occur.
Exothermic
Releases energy to the surroundings.
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Common Exam Questions
Explain the effect of a catalyst on a reaction profile.
3 marksmediumPaper 1
Model Answer
It lowers the activation energy, making the peak lower, but the overall energy change stays the same.
What examiners want to see
- ✓Mention lower activation energy.
- ✓State energy change unchanged.
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