p6

• Test for starch


  1. Add iodine solution

  2. Observe colour change

  3. Positive: Blue-black

  4. Negative: Brown
• Test for proteins


  1. Add Biuret reagent

  2. Observe colour change

  3. Positive: Mauve/purple

  4. Negative: Blue
• Test for reducing sugars


  1. Add Benedict's solution and heat

  2. Observe colour change

  Positive: Brick-red

  Negative: Blue
• Test for fats


  Crush food sample in mortar with ethanol

  Add distilled water

  Observe milky-white emulsion
• Precautions

  Take readings perpendicular to scale (avoid parallax error)

  Take readings from bottom of meniscus

  Stir solution to distribute all the components evenly

  Use burette/pipette instead of measuring cylinder

  Use heat shield for photosynthesis experiment (beaker of water) placed between the plant and the lamp to prevent the temperature from changing due to the changing light intensity