EXAMINERS REPORTfor2017 PHYSICAL SCIENCE PAPER 4 (ALTERNATIVE TO PRACTICAL)

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Jessie Kelly
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1 EXAMINERS REPORTfor2017 PHYSICAL SCIENCE PAPER 4 (ALTERNATIVE TO PRACTICAL) GENERAL OVERVIEW The Paper was fair since there was a balance between low and high order questions. The level of difficulty of the Paper was the same as that of 2016 question Paper. The paper assessed most of the paper 4 skills as stated in the syllabus. For instance, most experimental skills and investigations were assessed in the paper as demanded by the syllabus. Questions demand was to the level of the candidates. However, it was noted that: Candidates lacked technical language and scientific thinking and could not interpret the question phrased as draw conclusion, instead they drew diagrams. Candidates did not use appropriate technical terms, such as dissolving versus reacting, filtrating versus filtering, and eating/burning versus corroding. Best fitted line was omitted by candidates. It is therefore recommended that after proper data collection students should be exposed to the different methods of presenting data. For instance, tables, graphs, charts etc; as well as correct interpretation of data. Generally the performance was lower than in 2016 and most candidates scored below 16. Hence it was concluded that the 2017 candidates were of lower quality compared to their predecessors. PERFORMANCE ON INDIVIDUAL QUESTIONS Question 1 Determining suitability of glycerine to use in a thermometer (a) Candidates were to select one suitable item from given additional apparatus available to Renepile in the laboratory store room and state the reason for their choice. Expected Answers: (i) goggles, metal container and worn to protect eyes from glycerine fumes eyes will be protected, creates a water bath because glycerine is flammable. Common errors/misconceptions: digital stopwatch,funnel, electronic balance, use of goggles was for seeing better mainly to see mercury and alcohol not for safety, metal container being used as a good conductor or for storage of glycerine Performance: generally well done

2 (b) Candidates were to use Renepile s results to: (i) Measure the height of glycerine in the glass tube and record actual height using the given scale. Expected Answer: 380 ) in the table Common error/misconception: 38 Performance: well done Draw a graph of height against temperature for the glycerine. Expected diagram:all points correctly plotted joined with a straight line graph, correct graph drawn. Common errors/misconception: wrongly plotted coordinates, best fit line not drawn Performance: fairly done Recommendation: students should be exposed to questions involving graph drawing and scale reading more often. (iii) Use the graph to determine height at. Expected answer: value from graph Common errors/misconception: value of height without use of graph Performance: well performed (iv) Use the graph and provide a reason to conclude whether glycerine is suitable for use in the thermometer. Expected answer: The graph is a straight line/ height is directly proportional to temperature therefore it can be used. Common errors/misconceptions: height increases as temperature increases, glycerine expands as temperature increases, and glycerine is not suitable because only alcohol and mercury are used in thermometers as it is flammable, reason given not based on the graph Question 2 Investigating Ohm s law (a) Candidates were expected to state one additional piece of apparatus that will be used to vary current. Expected answer: variable resistor/rheostat Common errors/misconception: bulb, diode, resistor

3 (b) Candidates were required to complete a given circuit diagram. Candidates were expected to draw a correct working circuit with 3 cells in series and ammeter in series with correct symbols as the response. Common errors/misconceptions: cells were drawn in the resistor provided in the diagram, circuit without cell/battery, ammeter connected in parallel, fewer or more than three cells, and wrong symbol for cell/battery Performance: fairly done Recommendation: circuit diagrams with correct symbols and connections drawn from different electrical set-ups (c) Candidates were demanded to: (i) Record the reading shown on the meter. Expected answer: 2.5, Performance: well done Calculate values of Z 1 and Z 2 from voltage- current values given in the table. Expected answer: 3.75 and 4.08 Common errors/misconception: 3.17, 4.11 Performance: good (d) Evaluating methods (i) Candidates were required to state two errors that may result in the use of the drawn voltmeter. Expected answer: parallax error; zero error Common errors/misconceptions: parallel error, omission error, commission error, wrong calculations/recordings, human error Candidates were expected to suggest two precautions the student should take in her investigation. Expected answer: place eye perpendicular to scale; check zero errors; repeat to take average measurements. Common errors/misconceptions: start reading meter from zero, meter not suitable as it cannot read beyond six, place meter on flat surface, millimetres should be used not meters, use gloves and goggles Question 3

4 preparing a salt from a dilute sulphuric acid and a metal oxide (a) Candidates were required to state the stage at which heating is required. Expected answer: stage 1 and / or 3 Performance: well done Degree of attempt: good (b) Candidates were expected to describe how the student assembled the apparatus shown in Fig Expected answers: Fold filter paper to form a cone, and put it in the funnel; Put funnel into the flask Common errors/misconception: did not fold filter paper correctly, did not insert in the funnel, did not insert funnel into the flask, used beaker, flat bottomed flask, container, separation funnel Performance: badly done Degree of attempt: majority attempted the question (c) Candidates were required to state observation that the student would make to indicate neutralisation of acid. Expected answer: metal oxide in excess Common errors/misconceptions: metal oxide or metal no longer dissolving, reaction stops, no bubbles, no colour change with use of indicators (d) Suspicion of presence of copper (II) ions (i) Candidates were required to state the observation that led to suspicion. Expected answer: Blue salt solution/crystals Common errors/ misconceptions: litmus paper turns blue, green or white precipitate Recommendations: students should be able to identify different ions correctly Candidates were expected to describe how they would confirm the suspicion. Expected answer: addition of NaOH solution to the sample, and presence of blue precipitate confirms presence of copper (II) ions. Common errors/misconceptions: no sampling, non-blue precipitate, solution not precipitate, acidified the mixture Performance: not well done Recommendation: significance of sampling should be emphasised during testing (e) Candidates were expected to state and explain the safety precaution that student should take in stage 1.

5 Expected answers: gloves or resistant coats should be worn; acids are corrosive. Common errors/misconceptions:- precautions Question 4 addition of metal oxide to acid not acid to metal oxide, avoid contact/conduct with skin, avoid using bare hand, noise bag/back Explanations:- acids are explosive/flammable/dangerous/toxic, reaction of acid with metal oxide is explosive/dangerous, acids burn/eat/tear/ Investigating the use of red cabbage pigments solution as acid-base indicator (a) Candidates were expected to describe the use of given materials to extract the pigments. Expected answer: leaves (B) should be cut in small pieces; grind them wet with water (C) to effect extraction using a mortar and pestle (D); filter mixture using apparatus (A), and squeeze the residue for more filtrate. Common errors/misconception: students tested for starch in a leaf, use litmus paper, extraction by boiling, filtrate, use of green leaves and green pigment from red cabbage, instead of grinding students usedmortar for hammering, squeezing, hitting, crushing, beating, mortar as crucible, basin, petri dish, motor and pestle as pistil, pistol, piston, wooden spoon/rod, spatula,stick, addition of water after grinding not during Recommendations: emphasise should be made on organisms that they also have chemicals in them that can be tested too (b) Candidates were required to determine if the pigment solution extracted can be used as acid-base indicator. Expected answer: colour change should be noted in acid and in alkali when a few drops of extract are added in each solution placed in different test tubes. Common errors/misconceptions: pigment was not regarded as an acid-base indicator instead they used other indicators to test the pigment such as universal indicator, litmus paper, and phenolphthalein. Confused red colour of pigment for acidity Recommendation: students should be exposed to a wide range of indicators (c) Candidates were expected to ensure reliability of results. Expected answer: repeat with same or different acids and alkalis several times to ensure results are reproducible.

6 Common errors/misconception: gave expected colour changes for the wrongly stated indicators in (b), yes the results are reliable Performance: very poor performance (d) Candidates were required to draw a conclusion from the results. Expected answer: if the colour of extract in alkalis is always the same but different with acid, then it can be used as an indicator. Common error/misconception: actually drawing materials of A,B,C and D, ph scale, yes it s an acid-base indicator, Performance: very poor performance Recommendation: more exposure on command words such as draw, deduce, predict, determine. CONCLUSION: Generally, it was observed that candidates were not able to access marks on questions relating to apparatus. For examples, goggles for visibility, beaker for grinding or filtration, separating funnel for filtration. It is recommended that emphasis on naming, purpose or function and proper use of apparatus be made. Also errors associated with instruments should be highlighted, including how to read meters that have zero error.,

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education

*7531216271* UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education COMBINED SCIENCE 0653/61 Paper 6 Alternative to Practical October/November 2012