# Hydrogen gas can be produced by reacting methane with steam at high temperatures. The reaction is endothermic. Explain what the term endothermic reaction means and describe what happens to bonds during an endothermic reaction, including the relationship between energy taken in to break bonds and energy released when bonds are made.

> OCR A-Level Chemistry B: Salters (H433) — 3.2 Physical chemistry · Explain · 5 marks

> Hydrogen gas is increasingly used as a clean fuel. One method of producing hydrogen involves reacting methane with steam. This reaction requires a continuous supply of heat energy from the surroundings.

## Mark scheme (5 marks)

1. An endothermic reaction takes in energy from the surroundings
2. The temperature of the surroundings decreases in an endothermic reaction
3. Bond breaking is an endothermic process (energy is required/taken in to break bonds)
4. Bond making is an exothermic process (energy is released when bonds form in the products)
5. In an endothermic reaction the energy needed to break bonds in the reactants is greater than the energy released when bonds are formed in the products

## Key terms

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

## Related

- [Revision notes for OCR A-Level Chemistry B: Salters (H433)](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)

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Source: [GradeNine](https://www.gradenine.co.uk/q/hydrogen-gas-can-be-produced-by-3de9989f) · Published by Druglandscape Ltd.