Camping stoves burn propane gas to heat food. When propane burns in oxygen, carbon dioxide and water are produced. Explain why burning propane in a camping stove is an exothermic reaction, referring to the bonds broken and bonds made during the reaction.

OCR GCSE Chemistry A: Gateway Science (J248) — C3.3 Types of chemical reactions · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Propane is a fuel used in portable camping stoves. When propane burns, it reacts with oxygen to release energy to the surroundings.

Model answer (4 marks)

Breaking C–H and C–C bonds in propane requires energy (endothermic). Forming C–O bonds in CO₂ and O–H bonds in H₂O releases more energy (exothermic). The energy released in bond formation exceeds the energy absorbed in bond breaking, so net energy is given to the surroundings, raising their temperature.

Examiner tips

  • Use the terms ‘bond breaking is endothermic’ and ‘bond making is exothermic’.
  • Show the energy comparison and conclude that the reaction is exothermic.
  • Mention the products CO₂ and H₂O to link to the reaction.

Mark scheme (4 marks)

  1. Bond breaking is an endothermic process (energy is taken in to break bonds in the reactants)
  2. Bond making is an exothermic process (energy is released when bonds form in the products)
  3. The energy released making bonds in the products is greater than the energy taken in breaking bonds in the reactants
  4. Therefore energy is transferred to the surroundings, causing the temperature of the surroundings to increase

Key terms in this question

exothermic reaction

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