# Hydrogen peroxide decomposes into water and oxygen when manganese(IV) oxide is added as a catalyst. A student measures the temperature of the hydrogen peroxide solution before and after the reaction and notices a significant rise in temperature. Explain why the temperature of the solution rises, using the terms activation energy, bond breaking, bond forming, and energy.

> Cambridge International IGCSE Chemistry (0620) — 5.1 Exothermic and endothermic reactions · Explain · 4 marks

> Hydrogen peroxide decomposes into water and oxygen when manganese(IV) oxide is added as a catalyst. A student measures the temperature of the hydrogen peroxide solution before and after the reaction and notices a significant rise in temperature.

## Mark scheme (4 marks)

1. Energy is required to break bonds (in the reactants) / bond breaking is endothermic
2. Energy is released when new bonds are formed (in the products) / bond forming is exothermic
3. More energy is released in bond forming than is absorbed in bond breaking
4. The overall reaction is exothermic, so energy is transferred to the surroundings / solution, causing the temperature to rise

## Key terms

- [bond breaking](https://www.gradenine.co.uk/glossary/bond-breaking)
- [bond forming](https://www.gradenine.co.uk/glossary/bond-forming)
- [activation energy](https://www.gradenine.co.uk/glossary/activation-energy)
- [energy](https://www.gradenine.co.uk/glossary/energy)

## Related

- [Revision notes for Cambridge International IGCSE Chemistry (0620)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/hydrogen-peroxide-decomposes-into-water-and-0725eba3) · Published by Druglandscape Ltd.