# Explain why the combustion of methane is an exothermic reaction, in terms of the bonds broken and bonds formed during the reaction.

> AQA A-Level Chemistry (7405) — 3.1.8 Thermodynamics (A-Level only) · Explain · 5 marks

> Methane burns in oxygen according to the equation: CH₄ + 2O₂ → CO₂ + 2H₂O

## Mark scheme (5 marks)

1. Energy is required to break bonds (in the reactants)
2. Energy is released when bonds are formed (in the products)
3. The energy released (making bonds) is greater than the energy absorbed (breaking bonds)
4. Therefore there is an overall release of energy to the surroundings
5. This overall release of energy means the reaction is exothermic (temperature of surroundings increases)

## Key terms

- [exothermic](https://www.gradenine.co.uk/glossary/exothermic)

## Related

- [Revision notes for AQA A-Level Chemistry (7405)](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-the-combustion-of-methane-eee0909d) · Published by Druglandscape Ltd.