Describe the procedures and expected positive results for food tests to detect fat, starch, sugar, and protein.

Here are the details for the food tests described in the image:

• Test for Fat (Translucency Test)

  • Procedure:
    1. Rub a small sample of the food onto paper.
    2. Allow the paper to dry.
    3. Hold the paper in front of a light.
  • Positive Result: A translucent mark that allows light to pass through indicates the presence of fat.

• Preparation of Sample for Starch, Sugar, and Protein Tests

  • Procedure:
    1. Mash solid foods with a pestle and mortar.
    2. Put the food sample in about $5 \text{ cm}^3$ of water in a boiling tube.
    3. Boil gently for 1 minute.
    4. Allow it to cool and divide into 3 portions for the subsequent tests.

• Test for Starch (using Iodine solution)

  • Procedure: To one portion of the prepared food sample, add 5 drops of iodine solution.
  • Positive Result: A blue-black colour shows starch is present.

• Test for Sugar (using Benedict's test)

  • Procedure:
    1. To another portion of the prepared food sample, add 5 drops of dilute hydrochloric acid (CARE). Heat gently for 1 minute.
    2. Add 10 drops of Benedict's solution.
    3. Heat gently for 1 minute.
  • Positive Result: A green or orange-red precipitate shows glucose or sucrose is present.

• Test for Protein (using Biuret test)

  • Procedure:
    1. To the third portion of the prepared food sample, add $1 \text{ cm}^3$ of very dilute copper(II) sulphate solution.
    2. Add $1 \text{ cm}^3$ of sodium hydroxide solution.
    3. Mix and wait for 2 minutes.
  • Positive Result: A violet colour appears if protein is present.