decay practical

• why do we model decay using the enzyme lipase?

  • the decay process is very slow so it is hard to view it in a lesson
• how much lipase solution should we put in a test tube?

  • 5$cm^3$
• why does the milk + sodium carbonate solution turn purple?

  • sodium carbonate is alkaline and cresol red is purple in alkaline conditions
• why do we wait after putting the lipase solution and the milk+ sodium carbonate solution in the water?

  • so it reaches the same temperature as the water
• when do we start a timer?

  • when we put 1$cm^3$ of lipase solution into the milk + sodium carbonate solution
• what happens when we put lipase into the solution?

  • the lipase enzyme starts to break down fat molecules in the milk, this releases fatty acids and causes milk to become acidic
• what colour does cresol red change to in acidic conditions?

  • yellow
• what is the independent variable in the experiment?

  • the temperature
• what is the dependent variable?

  • time taken for milk solution to turn yellow [ cresol red ]
• what are the control variables?

  • volume of milk
  • volume of lipase
  • volume of sodium carbonate solution
  • volume of cresol red
• why do we use a new test tube every time we repeat the experiment?

  • to eliminate any traces of lipase that may trigger the reaction before we are ready
• why is it hard to decide the exact point to stop the timer?

  • because colour change is subjective depending on every person
• how can we reduce these subjectivity issues?

  • sharing data with other groups and calculating a mean
• how would you plot a graph for this experiment?

  • time taken goes on the y-axis and the temperature goes on the x-axis
• why are reactions slow at lower temperatures?

  • enzymes work slowly at lower temperatures
• why does the reaction slow down at warmer temperatures past the optimum temperature?

  • enzymes denatures at higher temperatures