Food tests teaching resources

Worksheets and lesson ideas to challenge students aged 11 to 16 to think hard about food tests (GCSE and Key Stage 3)
Food tests teacher brief

Overview: food is made from a variety of proteins, fats and carbohydrates in different proportions with small amounts of vitamins, minerals (ions) and water. Carbohydrates, fats and proteins are often large molecules that can be broken down into smaller molecules. Food tests provide a great opportunity to introduce students to some qualitative chemical tests, making some explicit links between biology and chemistry topics. All of these chemical tests can be learnt, but it’s even better if the chemistry behind them is understood.

Key concept: chemical tests can be used to detect the presence of carbohydrates, fats and proteins in food.

Prior knowledge: digestion, respiration, balanced diets

Misconceptions [scientific idea]: steak is protein [steak is made from protein and other food groups]; all proteins, fats and carbohydrates are the same [there are lots of different types of protein e.g. amylase and collagen, fats e.g. triglycerides and phospholipids, carbohydrates e.g. glucose and sucrose]; fats are not lipids [fats are solid lipids and oils are liquid lipids]

Teaching resources

Where to start?

Use a magnet to extract iron metal from a packet of iron fortified cereals. This provides an introduction to the idea that food is composed of different substances and this can then lead to a discussion of what the nutritional label tells us about what else is in cereal.

Testing foods for carbohydrates, fats and proteins

GCSE worksheet on testing for carbohydrates, lipids and proteins. This activity should be done once students have a secure understanding of how to test foods for proteins, carbohydrates and fats. The simple context of urine tests helps students to understand the rationale behind wanting to test for different food groups. Once students have been introduced to the challenge, ask them to create a results table. This will focus their plan of what to do during the experiment. Only when students have completed a suitable table can they carry out the experiment.

Linking chemistry to the food tests

What is happening to the copper (II) ions in the Benedict’s test? Why do we need to heat the solution? Why does starch produce a negative result with Benedict’s solution unless acid is added? Why are lipids insoluble in water but soluble in ethanol?

Thinking deeper

  • How could you make each food test quantitative?
  • Are all proteins the same?
  • Is there a difference between a lipid and a fat?
  1. Biological molecules
  2. Food tests
  3. Enzymes
  4. Photosynthesis
  5. Respiration

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