Required Practical: Decay

Question 1

Aim =

Answer 1

to investigate the effects of temperature on the rate of decay of fresh milk by measuring pH range

Question 2

The decay of foods like milk is influenced by…

Answer 2

temperature and the action of enzymes like lipase

Question 3

Lipase breaks down lipids into…

Answer 3

fatty acids and glycerol

Question 4

independent variable =

Answer 4

temperature of milk

Question 5

control variable =

Answer 5

type/volume of milk

Question 6

dependent variable =

Answer 6

time taken for pH to change

Question 7

1. label a test tube as l_______

Answer 7

lipase

Question 8

2. use a pipette to place…

Answer 8

5cm3 of lipase solution into the test tube

Question 9

2. in a test tube labelled milk, add

Answer 9

5cm3 of full fat, fresh milk

Question 10

3. add _____cm3 of _____ ________ to the milk to ensure that it is alkaline

Answer 10

7cm3 - sodium carbonate solution

Question 11

4. add a couple of drops of indicator ________ to the milk solution - it should turn PINK

Answer 11

phenolphthalein

Question 12

in alkaline solutions, what colour is phenolphthalein?

Answer 12

pink-purple

Question 13

5. place the two test tubes into a water bath measured at…

Answer 13

60 degrees

Question 14

6. once they are at 60 degrees for sure, add 1cm3 of the lipase enzyme and begin to…

Answer 14

stir after starting a timer

Question 15

7. once the pink colour has left, stop the

Answer 15

timer

Question 16

Repeat the experiment with different

Answer 16

temperature water baths

Question 17

IMPORTANT =

Answer 17

use different test tubes for the milk each time

re-do and take a mean, since observing colour change can be hard