RP10

• Why does milk sour when left at room temperature?

  Bacteria produce acidic molecules through enzymes
• What enzyme is used to model decay in the experiment?

  Lipase
• What does the indicator cresol red indicate in the experiment?

  It changes color based on acidity
• What color does cresol red turn in acidic conditions?

  Yellow
• What is the purpose of sodium carbonate in the experiment?

  To create an alkaline environment
• What is the first temperature used in the experiment?

  20 degrees Celsius
• What is the independent variable in this experiment?

  Temperature
• What is the dependent variable in this experiment?

  Time taken for milk to turn yellow
• What are the control variables in this experiment?

  Volumes of all solutions used
• Why is it important to use a clean test tube for each experiment?

  To avoid triggering reactions prematurely
• How can the difficulty of timing the color change be reduced?

  By sharing data and calculating a mean
• What is the relationship between temperature and enzyme activity in this experiment?


  • Enzymes work slowly at low temperatures
  • Optimum temperature allows fastest reaction rate
  • Higher temperatures can denature enzymes
• What happens to decomposing microorganisms at high temperatures?

  Enzymes denature and activity slows
• What should students expect in terms of questions on this practical?

  Many questions in the vision workbook
• What is the significance of plotting a graph of results?

  To visualize the relationship between variables