Required Practical 10:Decay

• What is the main objective of the practical described in the video?

  The main objective is to investigate the effect of temperature on the rate of decay of fresh milk by measuring the pH change.
• What is the role of bacteria in the decay process of milk?

  • Bacteria use enzymes to produce acidic molecules
  • This process causes milk to sour
• Why is decay considered a slow process in this practical?

  Because it is a slow process that is hard to observe in a lesson.
• How does the practical model decay using lipase?

  • Lipase is used to break down fat molecules in milk
  • This simulates the decay process
• What indicator is used in the experiment and what color does it turn in acidic conditions?

  The indicator used is cresol red, which turns yellow in acidic conditions.
• What is the first step in the practical procedure?

  Label a test tube for lipase and add five centimeters cubed of lipase solution.
• What is the significance of sodium carbonate solution in the experiment?

  • Sodium carbonate solution is alkaline
  • It causes the initial solution to be purple
• Why is it important to wait until the temperature of the solutions is the same as the water in the beaker?

  To ensure accurate measurement of the temperature's effect on the reaction rate.
• What is the dependent variable in this experiment?

  The dependent variable is the time taken for the milk solution to turn yellow.
• What is the independent variable in this experiment?

  The independent variable is the temperature.
• What are the control variables in this experiment?

  • Volumes of lipase solution
  • Volumes of milk
  • Volumes of sodium carbonate solution
  • Volumes of cresol red
• Why is it important to use a clean test tube for each experiment?

  To avoid triggering the reaction before it is ready.
• How can the effect of color change on timing be minimized in the experiment?

  • Share data with other groups
  • Calculate a mean at the end of the experiment
• What happens to the reaction rate at lower temperatures?

  The reaction is slow because enzymes work slowly at lower temperatures.
• What is the optimum temperature in the context of enzyme activity?

  The optimum temperature is the temperature at which the reaction takes place at its fastest rate.
• What occurs to the enzyme at temperatures higher than the optimum?

  The enzyme denatures, slowing down or stopping the reaction.
• How do decomposing microorganisms behave in different temperature conditions?

  • Work faster in warm conditions
  • Do not function well in hot conditions due to enzyme denaturation