required practicals

• Osmosis:

  IV: concentration of sugar solution

  DV: percentage change in mass of potato

  CV: length of potato, how long the potato is left in the solution
• Osmosis Equipment:

  • potato
  • cork borer
  • ruler
  • measuring cylinder
  • 5 boiling tubes
  • test tube rack
  • paper towels
  • scalpel
  • range of sugar solutions (different concentrations)
  • distilled water
  • top pan balance
• Osmosis steps:

  1. use cork borer to cute five potato cylinder of same diameter
  2. use scalpel to trim cylinders to 3cm
  3. measure mass of each potato cylinder using top ban balance and record masses
  4. measure 10cm3 of each concentration of sugar solution into 4 boiling tubes
  5. measure 10cm3 of distilled water and add to 5th boiling tube
  6. add one potato cylinder to each boiling tube
  7. leave for 48hrs
  8. remove potato cylinders and pat dry
  9. measure new mass of each cylinder using top pan balance
  10. calculate percentage change in mass of each potato cylinder and pot against concentration
• Osmosis Results:

  • if mass of potato cylinder stays same = sugar concentration in water is same to sugar concentration in potato
  • if mass of potato cylinder increases = water has moved from the sugar solution into the potato via osmosis
  • if mass of potato decreases = water has moved out of the potato into sugar solution via osmosis
• Photosynthesis:

  IV: distance from light source to pondweed

  DV: volume of carbon dioxide produced

  CV: temperature of water, carbon dioxide concentration
• Photosynthesis:

  How to change light intensity:

  • use lamp
  • move closer/further away from pondweed
• Photosynthesis equipment:

  • beaker
  • filter funnel
  • measuring cylinder
  • 10cm of pondweed
  • light source
  • metre ruler
  • stop clock
• Photosynthesis how to obtain accurate measurements for valid results:

  1. put 10cm of pondweed in beaker of water
  2. leave pondweed in light for few minutes before taking measurements
  3. use gas syringe to collect oxygen gas produced
  4. measure time oxygen collected using stop clock
  5. repeat measurements and calculate mean
• Photosynthesis method:

  1. put 10cm of pondweed in beaker of water
  2. leave pondweed in light for few minutes before taking measurements
  3. use gas syringe to collect oxygen gas produced
  4. use ruler to position beaker and pondweed 100cm away from light source
  5. measure time oxygen collected using stopwatch
  6. repeat measurements with light source at 80cm, 60cm, 40cm, 20cm
  7. calculate mean
• Photosynthesis results:

  closer the light source, the more oxygen gas produced in 3 minutes
• Microscopy:

  a microscope has x5 eyepiece lens
• Microscopy equipment:

  • microscope
  • slides of animal cells
  • slides of plant cells
• Microscopy method:

  1. put slide on stage
  2. turn nose piece to lowest objective lens
  3. adjust mirror on light so light passed through slide
  4. move stage close to lens
  5. slide must not touch lens
  6. use fine focussing knob to bring cells clear in focus
  7. use fine adjustment to bring cells back in focus
  8. change objective lens to x**
  9. refocus slide using focussing knob
  10. draw and label some of the cells
  11. write magnification underneath drawing
  12. multiply objective magnification by eyepiece magnification
• Microscopy conclusion:

  should be able to identify organelles
• Food Tests equipment:

  • food sample
  • test tube
  • pipettes
• Bendicts test for sugar method:

  1. add few drops of benedict’s solution to food sample
  2. boil test tube in water bath at 65 degrees
• Iodine test for starch:

  1. put food sample in test tube
  2. add few drops of iodine solution
• Ethanol test for lipids:

  1. put food sample in test tube
  2. add few drops of distilled water
  3. shake gently
• Biuret test for proteins:

  1. put food sample in test tube
  2. add 1cm3 of biuret solution A and B
  3. shake to mix
• Benedicts results:

  No sugar = blue

  Sugar = green/orange/red
• Iodine results:

  no starch = orange/brown

  starch = blue/black
• ethanol results:

  if lipids present milky layer at top
• Biuret results:

  no protein = blue

  protein = purple
• Enzymes:

  IV: pH of buffer solution

  DV: time taken for starch to break down into sugars

  CV: volume of starch solution, temperature of solution
• Enzymes equipment:

  • 10 test tubes
  • test rube rack
  • water bath
  • thermometer
  • spotting tile
  • measuring cylinder
  • pipettes
  • glass rod
  • stop watch
  • starch solution
  • amylase solution
  • iodine solution
  • buffer solutions (range of pH)
• Enzyme method

  1. Heat water bath to 35 degrees

  2. Add 2cm3 of each buffer solution and label each

  3. Add 20cm3 of starch solution in test tube labelled starch

  4. Put thermometer in starch to monitor temperature

  5. Add 10cm3 of amylase solution to another test tube and label amylase

  6. Put all test tubes in water bath

  7. Allow solutions to reach 35 degrees

  8. Add 1 drop iodine into each depression of spotting tile

  9. When all solution at 35 degrees, take on test tube of buffer solution and add 2cm3 of starch and 2cm3 of amylase solution and stir with glass rod

  10. Start stopwatch

  11. After 10 seconds, use pipette, add 2cm3 of solution to one depression

  12. Continue every 10 seconds