Sample answer Q2 (Paper 3)

Question 2 (Paper 3) - Latest format
Eg.
Plan a laboratory experiment to investigate the percentage of vitamin C content in each fruit. DCPIP (dichlorophenolindophenol) 0.1% solution is used to test the presence of vitamin C in the fruit juices.
[Apple, Orange, Watermelon]

Problem statement (3 marks)
1. What is the percentage of vitamin C content in watermelon, orange and apple?/ fruits? //
2. Does apple/orange/watermelon contain more vitamin C than orange/watermelon/apple? //
3. Which fruit has more percentage of vitamin C?
(Remember, all must be in question form. Change the aim into a question form. (kacang). No question mark, deduce 1 mark)

Hypothesis (MV+RV+R) (3 marks)
Watermelon has highest content of vitamin C compare to other fruits.
(Wrong hypothesis is accepted)

Materials & Apparatus (3 marks)
DCPIP solution, Standard Ascorbic Acid, Fruit juices / watermelon juice/orange juice/apple juice, Conical flask /beaker, Syringe with needle, Specimen tube

Procedure (3 marks)
K1 : Steps to set up the apparatus & materials
K2 : Steps to handle the fixed variable
K3 : Steps to handle the manipulated variable
K4 : Steps to handle the responding variable
K5 : Precautionary steps / steps taken to get accurate results / readings
(Examiners will be looking for all these points)

Eg.
K1 1. Three specimen tubes is labelled as A1, A2 and A3.
K2 2. Fill each specimen tubes with 1 ml of 0.1% DCPIP solution
K1 3 . Use a syringe to take 10 ml of standard ascorbic acid
K1 4 . Place the syringe needle into the DCPIP solution and release the ascorbic acid slowly into the DCPIP solution in A1
K4 5 Observe the change of DCPIP colour and stop releasing the ascorbic acid when the DCPIP become colourless/ no more blue traces
K4 6 Record the volume of ascorbic acid used to dicolourise the DCPIP solution.
K1/K5 7 Repeat steps 3 – 6 for A2 and A3 and calculate the average volume.
K1/K5 8 Juices from each of the fruits is obtained and kept fresh before used
K1/K2 9 Three specimen tubes is labelled as (B1, B2, B3, C1, C2, C3, D1, D2 and D3), and fill each specimen tubes with 1 ml of 0.1% DCPIP
K3 10 Repeat steps 2 – 7 by using fruit juices to replace the standard ascorbic acid.
K5 11 Do not shake the bottle to prevent from DCPIP is oxidated.
K4 12 Record the volume of watermelon juice, apple juice and orange juice that discolourise the DCPIP in the table and calculate the average volume
K4 13 Calculate the percentage of vitamin C in each of the fruit juice using the formula below:

Percentage of vitamin C in fruit juice =
                                                     volume of 0.1% ascorbic acid X 1.0 mgcm-1
                                                                 volume of fruit juice

Tak payah tulis all the Ks in front. For reference only.

Presentation of Data (2 marks)

No data is required. Just the title and the correct units.

Total : 17 marks