Food Tests
Q1.
Table 1 shows information about some food components in cow’s milk.
Table 1
 
 	Value per 500 cm3	Recommended Daily Allowance (RDA) for a typical adult	
Energy in kJ	1046	8700	
Fat in g	8.4	70.0	
Salt in g	0.5	6.0	
Calcium in mg	605	1000	
Vitamin B-12 in µg	4.5	2.4	
(a)  How much more milk would a typical adult have to drink to get their RDA for calcium compared with the amount of milk needed to get their RDA for vitamin B-12?
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Volume of milk = ______________________ cm3
(3)
(b)  Describe how a student could test cow’s milk to show whether it contains protein and different types of carbohydrate.
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(6)
A scientist investigated the effect of bile on the breakdown of fat in a sample of milk.
The scientist used an indicator that is colourless in solutions with a pH lower than 10, and pink in solutions with a pH above 10.
This is the method used.
1.   Add 1 drop of bile to a test tube and one drop of water to a second test tube.
2.   Add the following to each test tube:
•   5 cm3 of milk
•   7 cm3 of sodium carbonate solution (to make the solution above pH 10)
•   5 drops of the indicator
•   1 cm3 of lipase.
3.   Time how long it takes for the indicator in the solutions to become colourless.
The results are shown in Table 2.
Table 2
 
 	Time taken for the indicator to become colourless in seconds	
Solution with bile	65	
Solution without bile	143	
(c)  Explain why the indicator in both tubes became colourless.
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(3)
(d)  Give the reason why the measurement of the time taken for the indicator to become colourless might be inaccurate.
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(1)
(e)  Explain the difference in the results for the two test tubes in Table 2.
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(3)
(Total 16 marks)