Required Practicals - Decay

Question 1

What is the goal of the decay practical?

Answer 1

To investigate the effect of temperature on the rate of decay of fresh milk by measuring pH change.

Question 2

What is the apparatus list of the decay practical?

Answer 2

-a small beaker of full fat milk or single cream
-a small beaker of sodium carbonate solution
-a small beaker of lipase solution
-250cm3 beaker
-boiling tubes
-marker pen
-10cm3 plastic syringes
-thermometer
-A kettle
-Cresol red
-ice

Question 3

What is the method for the decay practical?

Answer 3

-label a boiling tube ‘lipase’ and add 5cm3 of lipase solution
-label a boiling tube ‘milk’ and add five drops of Cresol red solution
-Use a calibrated dropping pipette to add 5cm3 of milk to the ‘milk’ boiling tube
-Use another pipette to add 7cm3 of sodium carbonate solution to the ‘milk’ tube. The solution should be purple
-Put a thermometer into the ‘milk’ tube.
-Set up a water bath.
-Put both boiling tubes into the water bath. Wait until the contents reach the same temperature as water bath.
-Use another dropping pipette to transfer 1cm3 of lipase from the ‘lipase’ tube to the ‘milk’ tube. Immediately start the stopclock.
-Stir the contents of the ‘milk’ boiling tube until the solution turns yellow.
-Record the time taken for the colour to change to yellow.
-Repeat the investifation for different temperatures of water bath.
-Record results in a table.
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