General Science Report
9.0 GENERAL SCIENCE (237)
General science was tested for the first time in the year 2010. It had two theory papers, Paper one and 237/1 and paper two 237/2. Each paper had three sections A, B and C. Section A had biology questions with 34 marks, section B had Chemistry questions with 33 and section C had physics questions with 33 marks. Each of the papers was marked out of 100.
9.1 CANDIDATES OVERALL PERFORMANCE
The overall performance of candidates in general science in the year 2010 was as shown in the table below.
Table 15: Candidates Performance in General Science
From the table it can be observed that:
9.1.1 The candidature of general science was very low.
9.1.2 The performance in both papers of general science was very poor.
The following is a discussion of some of the questions that candidates had difficulties in responding to.
9.2 PAPER 1(237/1)
9.2.1 SECTION A: BIOLOGY
No difficult questions were reported in Paper 1.
9.2.2 SECTION B: CHEMISTRY
In the paper 1 Chemistry section question that challenged most candidates were question numbers 16,18 and 19.
They are discussed below.
The table below gives information about atoms of I-I, J, K, Land M. Use it to answer the questions that follow:
(a) Select an atom:
(i) of an element in group 8 of the periodic table; (1 mark)
(ii) whose mass is ii (I mark)
(b) Select atoms which represent isotopes of an element. Give a reason. (2 marks)
Candidates were required to identify elements given in a periodic table.
WeaknessesMost candidates did not identify group 8 elements and isotopes from the elements given
(a) (i) K
(b) J and L; have the same atomic numbers but different atomic masses.
The table below gives information about substances N. P, Q and R.
(a) Select a substance that is likely to he hydrogen chloride. (1 mark)
(b) Which letter represents a substance that is likely to have:
(i) metallic bonding: (1 mark)
(ii) ionic bonding? (I mark)
Candidates were required to identify substances with metallic and ionic bonding.
WeaknessesCandidates did not bow characteristics of substances with metallic and ionic bonding.
Candidates were required to label cathode and explain observations made on anode.
In the physics section of paper 1 candidates had difficulties in questions 25, 27, 30 and 34.
(b) (i) Q
The diagram below represents a set up that was used to show the effect of an electric current on aqueous Copper (II) Sulphate using carbon electrodes.
(a) On the diagram, label the cathode. (I mark)
(b) State and explain the observation made at the anode. (2 marks)
WeaknessesCandidates confusing cathode with anode and were unable to explain what happens during electrolysis.
(a) See the diagram. (electron on the left side).
(b) The anode becomes smaller. This is because it dissolves.
9.2.3 SECTION C: PHYSICS
A uniform metre rule pivoted at the 30 cm mark, was balanced by a weight of 2 N suspended from the 5cm mark. Determine the mass of the metre rule. (take g = iON/kg) (3 marks)
WeaknessesCandidates were unable to locate the position of centre of gravity for the ruler and apply the principle of moments.
A bimetallic strip is made by riveting together two strips of different metals E and F. When hot, the strip is straight as shown in figure la. When it is allowed to cool to room temperature, the strip bends as shown in figure lb.
Explain the cause of the bending. (2 marks)
WeaknessesCandidates responded as if the bi-metallic strip was expanding after heating rather that contracting when cooling. This was a clear indication of inability to apply the acquired knowledge to a different situation.
Expected responseF. contracts more than E hence becomes shorter than E.
A thin copper wire was stretched by loading it with increasing forces and the extension in millimeters measured. The results obtained are shown in the table below.
(a) Determine the value of L in the table. (I mark)
(b) State with a reason what is observed on the length of the wire when all the weights
are removed. (2 marks)
WeaknessesMost candidates knew the observation but were not able to state the reason for the observation when all the weights are removed
Expected response(a) L=1.8mm
(b) Wire will be longer than the original length because the force had exceeded the elastic limit.
V starts at a v1' straight line
point drops down to zero and to negative. of negative gradient.
(a) FigureS. shows a light tennis ball attached to two identical metal bars. Mark with X the approximate position of the centre of gravity of the set up. (1 mark)
(b) A certain model of a lorry has its centre of gravity 1.5 m above the ground. State how the model can be improved to increase its stability with the centre of gravity remaining
at the same height. (1 mark)
WeaknessesMost candidates lacked knowledge of stability and were not able to express themselves.
Expected responseFigure 8
9.3 PAPER 2 (237/2)
9.3.1 SECTION A: BiOLOGY
(a) State one survival value of positive phototropism
Most candidates were unable to link positive phototropism to exposure of the shoot to light.
Expected responseEnables a plant to expose its shoot/leaves to light (for photosynthesis);
Advice to teachers
Learners should be made to understand the survival value of each of the tropic responses in plants.
(b) Explain how the following adaptations reduce transpiration in xerophytes:
(i) sunken stomata; (ii) thick cuticle.
Most candidates were unable to relate the structural adaptations to reduced transpiration rates.
(b) (i) Accumulates moisture in the sub-stomatal air spaces leading to
reduced diffusion gradient;
(ii) Increases the diffusion distance;
Advice to teachers
Learners should be taken through the physical adaptations of xerophytes and how each of the adaptations enables them to survive in their habitat.
(b) In a family of four children, the father has blood group A while the mother has blood group B. One of the children has blood group 0. State the genotypes of the following:
(iii) Child with blood group 0. Most candidates could not come up the correct genotypes
Advice to teachers
Learners should be properly taken through the process of genetic inheritance using flow diagrams or Punnet
9.3.2 SECTION B: CHEMISTRY
In paper 2 Chemistry section, the questions that were most challenging to candidates were numbers 12, 13, 15 and 20 which are discussed below.
In a laboratory experiment, hexane was heated and passed over strongly heated pieces of
broken pot, as shown in the diagram below.
(a) Name the type of reaction which occurred in the heated boiling tube. (1 mark)
(b) Why are the pieces of broken pot used? (I mark)
(c) One of the products in the gaseous mixture is propane. Draw and name the other
product in the mixture. (2 marks)
Candidates required to state products formed when hexane decomposes on heating.
WeaknessesLack of knowledge on naming of organic compounds and their structures.
(b) Acting as a catalyst;
(a) Explain why nitrogen (IV) Oxide causes pollution to the environment.
(b) The figure below represents the set up that was used to prepare nitrogen (IV) Oxide.
Lead Iii NH rot a
(i) Write a chemical equation for the above reaction that gives nitrogen (IV) Oxide.
soaked in hexene
Mixture of ice and common salt
(ii) What is the role of the mixture of ice and common salt? (1 mark)
Candidates required to state products formed when lead (ii) nitrate decomposes and write chemical reaction.
WeaknessesLow knowledge on formation of acid rain and effect of heat on substances.
(a) It forms acid rain;
Acid rain kills organism/corrodes
(b) (1) Oxygen;
(ii) to separate NO2 from Oxygen;
(a) What is meant by molar heat of fonnation of a substance? (1 mark)
(b) In the industrial production of ammonia, hydrogen and nitrogen react as shown in the
(i) What is the molar heat of formation of ammonia in kilojoules? (1 mark)
(ii) Explain the effect of increasing the temperature of the reaction, on the yield of
ammonia. (2 marks)
Candidates required to understand heat of formation of substances and how equilibrium is affected.
WeaknessesCandidates did not understand how change in temperature affects equilibrium of a reaction.
(a) The heat change when one mole of a substance is formed from its constituent elements at standard conditions;
(b) (i) -46.2 KJ/mole;
(ii) -the yield of ammonia will reduce;
-increase in temperature favours the reverse reaction which is the formation of hydrogen and
nitrogen. (This is because reaction for formation of ammonia is exothermic);
(a) Aluminium metal is extracted from its oxide by the electrolytic method while
iron is extracted by reduction method using carbon. Arrange the elements, aluminium,
iron and carbon in the order of reactivity starting with the most reactive. (2 marks)
(b) During the extraction of aluminium by electrolysis, the mass of the anode decreases.
Give a reason. (1 mark)
(c) Give one reason why aluminium is used in making sauce pans.
Candidates required to arrange elements in order of reactivity based on their methods of extraction.
WeaknessesCandidates had no enough understanding of the methods used for metal extraction and how this can be used to arrange them in order of their reactivity.
(a) Aluminium, Carbon, Iron. (2 marks
(if order is wrong but carbon is in the middle (1 mark)
(b) Oxygen produced at the anode reacts with the anode, thus depleting it;
(c) Aluminium is a good conductor of heat;
9.3.3 SECTION C: PHYSICS
Figure 3 shows a power supply passing current through two resistors connected in series.
Most candidates were not able to calculate the potential difference across R1 of R2.
(a) Calculate the potential difference V across R1.
(b) Determine the resistance R,. (2 marks)
= 1.5 x5 7.5V
and hence determine the resistance
V = 107.5 = 2.5V (1)
R 2.5=1.67 ohms
Figure 4 shows the image I of the object 0 produced by a converging tens.
(a) On the figure, construct a ray diagram to show how the image is formed. (2 marks)
(h) Use the ray diagram to determine the focal length of the lens. (I mark)
WeaknessesCandidates were unable to construct ray diagrams to show the image formed and hence determine the focal length of the lens. Most candidates drew lines instead of rays.
A room uses five bulbs for lighting. Each bulb is rated 240V, 60W. Determine the energy in
kWh consumed by the bulbs in 6 hours. (3 marks)
WeaknessesCandidates were not able to calculate the total energy consumed by the five bulbs. Many had no idea of the formula to be applied.
Expected responseEnergy Pxt (1)
= 60 x io- x 5 x 6 1.8 Kwh (1)
Advice to teachers
Emphasis should be made on:
Drawing ray diagrams with arrows to indicate the direction.
Application of knowledge in different situations.
Mastery of formulae in all topics.
Proper mastery of content by giving practice.
9.4 GENERAL ADVICE TO TEACHERS
9.4.1 The whole syllabus should be effectively covered during instruction because examination items will be sampled from the entire syllabus.
9.4.2 The teacher/school should acquire the relevant reference materials and assist candidates to obtain and use the recommended textbooks.
9.4.3 The use of textbooks by teachers should always be guided by the syllabus. The specific objectives stipulated in the syllabus should be correctly interpreted to ensure the topics in question are taught adequately and effectively.
9.4.4 A variety of teaching methods and resources should be utilised by teachers to ensure that the content is effectively delivered during instruction.
9.4.5 Resource persons/guest speakers and field visits should be arranged and used in areas where the teacher and the school lack the resources to teach the topic/lesson effectively.
9.4.6 All the suggested practical activities in the syllabus should be carried out to prepare candidates adequately for questions that require application of psychomotor skills acquired during instruction.
What it takes