RP10 Decay

Question 1

describe how you would investigate the effect of temperature on the rate of decay of milk

Answer 1

• place full-fat milk and cresol red indicator in a test tube, and lipase solution in another. place both test tubes in a water bath and allow the temperature to equilibrate.
• transfer drops of lipase into the other test tube and start stopwatch. stir until solution turns yellow and record the time taken.
• repeat at different temperatures and plot graph of temperature (x) against time taken (y).

Question 2

why does the addition of lipase accelerate the decay of milk?

Answer 2

lipase is an enzyme which catalyses the breakdown of lipid to fatty acids and glycerol. it provides an alternative reaction route with a lower activation energy

Question 3

why does the pH of the solution change during this reaction?

Answer 3

fat in milk is broken down into fatty acids by the enzyme lipase, lowering the pH

Question 4

what colour is cresol red in alkaline and acidic solutions?

Answer 4

alkaline: purple
acidic: yellow

Question 5

why does an increase in temperature increase the rate of this reaction?

Answer 5

enzyme and reacting particles have a higher kinetic energy and collice more frequently, leading to a faster rate of reaction

Question 6

why might the rate of reaction decrease if the temperature is very high?

Answer 6

enzymes become denatured as active site changes shape - cannot catalyse reaction