Decomposition

• gardeners and farmers try to provide optimum conditions for rapid decay of waste and biological material
• the compost produced is used as natural fertiliser for growing garden plants or crops
• Anaerobic decay produces methane gas
• Biogas generators can be used to produce methane gas as a fuel
• MILK PRACTICAL:

  1. Measure out 5cm^3 of lipase solution and add it to a test tube. Label with an 'L'
  2. Measure out 5cm^3 of milk and add it to a different test tube.
  3. Add 5 drops of phenolphthalein indicator to the tube containing milk
  4. Measure out 7cm^3 of sodium carbonate solution and add it to the tube containing milk. This should make the solution alkaline and turn pink
  5. Put both tubes into a water bath at 30C and leave them to reach the temperature. Measure this with a thermometer
• MILK PRACTICAL:

  1. Once the tubes have reached 30C, use a calibrated dropping pipette to put 1cm3 of lipase solution into the milk tube and start a stopwatch immediately
  2. stir contents with a glass rod, the enzyme will start to decompose the milk
  3. as soon as the solution loses the pink colour, stop the stopwatch and record how long it took for the colour to change in a table
  4. repeat the experiment at a range of different temperatures and make sure to carry out the experiment three times at each temperature, then calculate a mean time taken
  5. use results to calculate rate of decay as rate = 1000/time