Question detail

A science teacher asks a student to identify the contents of four unlabelled test tubes (A, B, C, D) using appropriate food tests. The student performs the following: * **Test 1 (Starch):** Adds iodine solution to each tube. Tube B turns blue-black. Others remain yellow-brown. * **Test 2 (Reducing Sugars):** Adds Benedict's solution to new samples from each tube and heats them in a water bath. Tube A turns orange, Tube D turns green. Tubes B and C remain blue. * **Test 3 (Protein):** Performs the Biuret test on new samples. Tube C turns lilac/purple. Others remain blue. Discuss the conclusions the student can draw about the contents of each test tube. Explain how the student could improve the reliability of their results, distinguishing between method improvements and reliability improvements. [6 marks]

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