Investigations

• Investigation about how fast a product appears depending on the temperature:

  1. The enzyme catalase catalyses the breakdown of hydrogen peroxide into hydrogen and oxygen,
  2. With a pipette, add a set amount of hydrogen peroxide to a boiling tube and put the tube in a water bath at 10ºC.
  3. Add a source of catalase to the hydrogen peroxide and quickly attach a bung to connect the boiling tube with a measuring cylinder.
  4. Record how much oxygen is produced in the first minute.
  5. Repeat several times at different temperatures.
• Investigation about how fast a substrate disappears depending on the temperature:

  1. The enzyme amylase catalyses the breakdown of starch into maltose.
  2. Put a drop of iodine solution into each well of a spotting tile.
  3. Put the starch solution in a water bath.
  4. When it is of the correct temperature, add the amylase enzyme.
  5. Every ten seconds, drop a sample of the mixture into a well using a pipette.
  6. When the iodine solution remains browny-orange, record the total time taken.
• Investigation of diffusion in non-living systems:

  Phenolphthalein is a pH indicator. It's pink in alkaline solutions and colorless in acidic solutions

  1. Make some agar jelly with phenolphthalein and dilute sodium hydroxide. The jelly will be pink.
  2. Put some dilute hydrochloric acid in a beaker. Cut out a few cubes from the jelly and put them in the beaker of acid.
  3. The cubes will eventually turn colorless as the acid diffuses into the agar jelly and neutralises the sodium hydroxide.
• Investigation of osmosis in living system - potato cylinders:

  1. Cut a potato into identical cylinders.
  2. Get some beakers with different solutions in them: one should have water and another should be a very conncentrated sugar solution. You can have a few others with conncentrations in between.
  3. Measure the length of the cylinders.
  4. Leave a few cylinders in each beaker for half an hour or so.
  5. Take them out and measure their lengths again.

  CONCLUSION: If the cylinders have drawn water in by osmosis, they'll be a bit longer. If water has been drawn out, they'll have shrunk a bit.
• Investigation of osmosis in non-living system - visking tubing:

  1. Fix a Visking tubing over the end of a thistle funnel.
  2. Pour some sugar solution down the glass tube into the thistle funnel.
  3. Put the thistle funnel into a beaker of pure water and measure where the sugar solution comes up to on the glass tube.
  4. Leave it for some time, then measure where the solution is in the glass tube.

  CONCLUSION: Water should be drawn through the Visking tubing by osmosis and this will force the solution up the glass tube.