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IGCSEBiology
Trial Class

Original practice · 5 questions · 15 marks · about 17 minutes

Food Tests Practice Questions

Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.

These questions test your ability to describe and interpret the standard food tests for starch, reducing sugars, proteins, lipids, and vitamin C.

Before you open the answers

  • Attempt every question without notes.
  • Show working for calculations and write complete biological statements.
  • Use the suggested time as a guide, not a strict limit on the first attempt.

These are original practice questions. They do not reproduce an official Cambridge paper or official mark scheme.

  1. Question 1

    Paper 2 Both 4 marks Difficulty 2/5

    Describe the Benedict's test for reducing sugars. Include the reagent used, the method, and the positive result.

    Show model answer and marking guidance
    1. Add Benedict's reagent (blue) to the food sample.
    2. Heat in a water bath (not directly over flame).
    3. If reducing sugar is present, colour changes from blue → green → yellow → orange → brick-red.
    4. The final colour indicates the relative amount of sugar present.

    Watch for: Heating over a Bunsen flame instead of a water bath: this is unsafe and loses marks.

  2. Question 2

    Paper 2 Core 2 marks Difficulty 1/5

    A student adds iodine solution to a food sample and it turns blue-black. What does this show?

    Show model answer and marking guidance
    1. Starch is present in the food sample.
    2. Iodine solution changes from brown/yellow to blue-black in the presence of starch.

  3. Question 3

    Paper 4 Extended 3 marks Difficulty 3/5

    A student tests an unknown food and gets these results: Benedict's test: stays blue; iodine test: stays brown; Biuret test: turns purple; emulsion test: white emulsion forms. Identify the nutrients present.

    Show model answer and marking guidance
    1. No reducing sugar (Benedict's negative).
    2. No starch (iodine negative).
    3. Protein present (Biuret positive: purple).
    4. Lipid/fat present (emulsion test positive).

  4. Question 4

    Paper 5/6 Both 3 marks Difficulty 3/5

    Explain why food samples should be in liquid form before testing, and why a water bath is used for Benedict's test rather than a Bunsen burner.

    Show model answer and marking guidance
    1. Liquid form allows the reagent to mix thoroughly with the sample.
    2. A water bath provides even, controlled heating.
    3. Direct heating with a Bunsen could cause the liquid to boil violently / spit, which is a safety hazard.

  5. Question 5

    Paper 4 Extended 3 marks Difficulty 4/5

    Sucrose is a non-reducing sugar. Describe how you would test for sucrose using Benedict's reagent.

    Show model answer and marking guidance
    1. First, boil the sample with dilute hydrochloric acid to hydrolyse sucrose into glucose and fructose.
    2. Neutralise the acid by adding sodium hydrogencarbonate.
    3. Then carry out the Benedict's test: add reagent and heat in a water bath.

Mark the set consistently

Award a point only when the idea is clearly present in the written answer. Correct any missed point in a complete sentence, then test the same skill on a different question several days later.

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