Lesson 4 of 9

Energy in food and fuels

Goal: Compare the energy in foods and fuels.

Puzzles for this lesson

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An apple, bread, a bar of chocolate, peanuts and a cucumber on a table

Food and fuels are chemical energy stores. The energy in them is measured in kilojoules (kJ).

  • 1 kJ = 1000 J. A joule is small: lifting an apple by one metre takes about 1 J.
  • A food label gives the energy in 100 g of the food, so that you can compare one food with another.
  • Fuels store even more. Burning 1 g of petrol transfers about 45 kJ. Eating 1 g of chocolate provides about 22 kJ.

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Key words in this lesson

Joule The unit of energy

For teachers: AQA 3.3.1 · Pearson Edexcel 28.1