As fuels
3 marks · EasyMethane is a hydrocarbon fuel. Answer the following questions about its combustion.
Write a word equation for the complete combustion of methane.
Give the names of the two products formed in this reaction.
Explain why methane releases energy when it burns completely in air.
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(a) methane + oxygen → carbon dioxide + water
(b) carbon dioxide and water
(c) Energy is released because new bonds are formed in carbon dioxide and water, releasing heat.
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Marking points
B1 (a) · 1 mark · Correct word equation for the complete combustion of methane
B1 (b) · 1 mark · States both products as carbon dioxide and water
M1 (c) · 1 mark · Links energy released to bond formation in products (or recognises exothermic reaction)
Worked solution
a) methane + oxygen → carbon dioxide + water
b) The products are carbon dioxide and water.
c) Chemical energy is released because the bonds formed in carbon dioxide and water release more energy than is used to break the bonds in methane and oxygen.