NAME………………………………………………………. INDEX NO…………………/…………
SCHOOL……………………………………………… CANDIDATES SIGNATURE………………
ADMISSION NUMBER……………………. CLASS………………………
231/3
BIOLOGY
(PRACTICALS)
Paper 3
November, 2020
13/4 Hours
MOKASA EXAMINATIONS 2020
Kenya Certificate of Secondary Education (K.C.S.E)
INSTRUCTIONS TO CANDIDATES
Write your name and Index Number in the spaces provided above.
Sign and write date of examination in the spaces provided above.
Answer ALL questions in the spaces provided in the question paper.
You are NOT allowed to start working with the apparatus for the first 15 minutes of the 13/4
Hours allowed for this paper. This time is to enable you to read the question paper and make sure
you have all the chemicals and apparatus that you may need.
All workings MUST be clearly shown where necessary.
Mathematical tables and silent electronic calculators may be used.
For Examiners use only.
Section Question Maximum Score Candidates Score
1
14
2
12
14
3
TOTAL
40
SCORE
This paper consists of 7 Printed pages.
Candidates should check the question paper to ensure that all the
Papers are printed as indicated and no questions are missing
(MOKASA2020) Page 1
, 1. You are provided with specimen labeled A. Obtain a cube measuring 1cm by 1cm from the specimen.
(a) Crush the cube using mortar and pestle, place the crushed parts in measuring cylinder, add 2 ml of
hydrogen peroxide and quickly determine the volume of foam after 20 seconds and fill the table below.
(1 mark)
Specimen Volume of foam
Crushed cube A
Explain why the reaction in (a) above occurs in living cells. (2 marks)
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
(b) You are provided with a solution labeled B, unboiled C1 and boiled C2. Place 2ml of the solution B
into two test tubes and carry out a food test using the reagents provided. Record your observation in the
table below. (2 marks)
FOOD PROCEDURE OBSERVATION CONCLUSION
SUBSTANCE
Place 2ml of solution B into four test tubes labeled F, G, H and K. Carry out the following steps.
(i) To test tube labeled F and its contents add 3ml solution C1 and 3 ml distilled water.
(ii) To test tube labeled G and its contents, add 3ml solution C1 and 3 ml dilute hydrochloric acid.
(iii) To test tube labeled H and its contents, add 3 ml solution C 1 and 3 ml sodium hydroxide solution.
(iv) To test tube labeled K and its contents, add 3 ml solution C2.
(v) Place the test tubes in a water bath at 37 0C for 20 minutes.
(vi) Carry out a Benedict’s test and fill the table below. (4 marks)
(MOKASA2020) Page 2
SCHOOL……………………………………………… CANDIDATES SIGNATURE………………
ADMISSION NUMBER……………………. CLASS………………………
231/3
BIOLOGY
(PRACTICALS)
Paper 3
November, 2020
13/4 Hours
MOKASA EXAMINATIONS 2020
Kenya Certificate of Secondary Education (K.C.S.E)
INSTRUCTIONS TO CANDIDATES
Write your name and Index Number in the spaces provided above.
Sign and write date of examination in the spaces provided above.
Answer ALL questions in the spaces provided in the question paper.
You are NOT allowed to start working with the apparatus for the first 15 minutes of the 13/4
Hours allowed for this paper. This time is to enable you to read the question paper and make sure
you have all the chemicals and apparatus that you may need.
All workings MUST be clearly shown where necessary.
Mathematical tables and silent electronic calculators may be used.
For Examiners use only.
Section Question Maximum Score Candidates Score
1
14
2
12
14
3
TOTAL
40
SCORE
This paper consists of 7 Printed pages.
Candidates should check the question paper to ensure that all the
Papers are printed as indicated and no questions are missing
(MOKASA2020) Page 1
, 1. You are provided with specimen labeled A. Obtain a cube measuring 1cm by 1cm from the specimen.
(a) Crush the cube using mortar and pestle, place the crushed parts in measuring cylinder, add 2 ml of
hydrogen peroxide and quickly determine the volume of foam after 20 seconds and fill the table below.
(1 mark)
Specimen Volume of foam
Crushed cube A
Explain why the reaction in (a) above occurs in living cells. (2 marks)
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
(b) You are provided with a solution labeled B, unboiled C1 and boiled C2. Place 2ml of the solution B
into two test tubes and carry out a food test using the reagents provided. Record your observation in the
table below. (2 marks)
FOOD PROCEDURE OBSERVATION CONCLUSION
SUBSTANCE
Place 2ml of solution B into four test tubes labeled F, G, H and K. Carry out the following steps.
(i) To test tube labeled F and its contents add 3ml solution C1 and 3 ml distilled water.
(ii) To test tube labeled G and its contents, add 3ml solution C1 and 3 ml dilute hydrochloric acid.
(iii) To test tube labeled H and its contents, add 3 ml solution C 1 and 3 ml sodium hydroxide solution.
(iv) To test tube labeled K and its contents, add 3 ml solution C2.
(v) Place the test tubes in a water bath at 37 0C for 20 minutes.
(vi) Carry out a Benedict’s test and fill the table below. (4 marks)
(MOKASA2020) Page 2
