Practicals paper 2 Flashcards
Milk decay practical
1) Measure out 5m3 of lipase solution and add it to a test tube, label it
2) add 5 cm3 of milk to a different test tube, label it milk
3) Use universal indicator paper or 5 drops of phenolphthalein to determine the pH of the milk in the three beakers
4) add 7cm3 of sodium carbonate solution and add it to the tube containing ilk and phenolphthalein, this makes the solution in the tube alkaline, so it should turn pink
5) put the thermometer in the test tube containing milk
6) put both of the test tubes in a hot water bath at a chosen temperature, 20 degree
7) When the temperatures of our solutions reach 20 degrees, put 1cm3 of the lipase solution into the milk tube and start a stopwatch straight away
8) stir the contents of the tube with a glass tube the enzyme will start to decompose the milk, breaking the fat molecules, releasing fatty acids, which causes the milk solution to become acidic
9) the indicator will turn white, as soon as this happens stop the stopwatch and record how long the colour change took in a table
10) repeat the experiment with a range of different temperature
11) calculate the rate decay in the units s-1
rate = 1000/time
