required practicals

• microscopy

  1. place slide on the stage and use clips to hold the slide
  2. select the lowest power objective lens
  3. position the lens so it almost touches the slide
  4. slowly turn the coarse focusing dial
  5. adjust the focusing dial accordingly
  6. look through the eye piece
• Potato experiment


  1. Peel the potato

  2. Use a cork borer to make three cylinders of potato, all with the same diameter

  3. Use a scalpel to trim the cylinders to the same length (3cm)

  4. Measure the length of each cylinder and the mass using a balance

  5. Place each cylinder into a test tube with 10cm cubed of a 0.5 molar sugar solution, 0.25 molar sugar solution, and 10cm cubed distilled water (no dissolved substances)

  6. Leave overnight

  7. Remove potato cylinders and gently roll them on a paper towel to remove any surface moisture

  8. Measure the length and mass

  9. Calculate percentage change = change over original times 100
• food tests

  1. take food samples and grind this with distilled water using a mortar and pestle, to make a paste
  2. transfer the paste to a beaker and add more distilled water
  3. stir the chemicals in the food so it dissolves in water
  4. filter the solution to remove suspended food particles
• testing for starch

  1. place 2cm cubed of food solution into a test tube
  2. add a few drops of iodine solution (orange) if starch is present solution will turn blue-black, if not it will stay orange
• testing for sugars

  1. 2cm cubed of food solution
  2. add 10 drops of benedict solution (blue)
  3. place test tube in a beaker and half fill it with hot water
  4. leave for 5 mins
  5. if sugar present, it will change colour (green, yellow, brick red) less to lot
• testing for protein

  1. 2cm cubed of food solution
  2. 2cm cubed of biuret solution (blue)
  3. if protein present, solution will turn lilac
• testing for lipids

  (don't filter solution because lipid molecules can stick to filter paper)

  1. 2cm cubed of food solution
  2. add few drops of distilled water and ethanol
  3. gently shake solution
  4. if lipids produced, solution will turn cloudy
• effect of pH on amylase

  1. place one drop of iodine solution in each well of spotting tile
  2. 2cm of starch solution, 2cm of amylase solution and 2cm of pH 5 buffer solution
  3. place all test tube in a water bath at 30C
  4. combine 3 solutions into one test tube and mix using a stirring rod, return it into water bath and start the stopwatch
  5. after 30s, transfer one drop of solution into a well containing iodine using a stirring rod
  6. iodine should turn blue-black, take sample until the iodine remains orange, reaction completed (starch present)
  7. repeat using different pH buffers
• photosynthesis

  1. place a boiling tube 10cm away from an LED light source (don't release much heat)(if bulb MUST be used, place a beaker of water in between the bulb and tube)
  2. fill boiling tube with sodium hydrogen carbonate solution, which releases carbon dioxide
  3. put piece of pondweed in tube and leave the cut end at the top
  4. leave for 5 mins, bubbles of oxygen should be released
  5. start stopwatch and count the number of bubbles produced in 1 min
  6. repeat and calculate mean time
  7. repeat with 20cm, 30cm and 40cm
• problems with photosynthesis practical

  • number of bubbles may be too fast to count
  • bubbles have different sizes
  • solution= place pond weed under a funnel and catch the bubbles in a measuring cylinder, measure volume of oxygen gas produced
• inverse square law = double the distance, the light intensity falls by four times

  as we need this for photosynthesis, the number of oxygen bubbles fall by four times