Coimisiún na Scrúduithe Stáit State Examinations Commission
LEAVING CERTIFICATE EXAMINATION 2009
PHYSICS & CHEMISTRY
ORDINARY LEVEL CHIEF EXAMINER’S REPORT
HIGHER LEVEL CHIEF EXAMINER’S REPORT
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CONTENTS 1. General Introduction 3
2. Ordinary Level 4
2.1 Introduction 4
2.2 Performance of Candidates 4
2.3 Analysis of Candidate Performance 6
2.4 Conclusions 21
2.5 Recommendations to Teachers and Students 22
3. Higher Level 23
3.1 Introduction 23
3.2 Performance of Candidates 23
3.3 Analysis of Candidate Performance 25
3.4 Conclusions 42
3.5 Recommendations to Teachers and Students 43
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1. General Introduction
1.1 The Syllabus
The Leaving Certificate Physics & Chemistry syllabus consists of a series of topics drawn from Physics and from Chemistry. The syllabus can be found in the Rules and Programme for Secondary Schools published by the Department of Education and Science.
1.2 Candidature
Table 1 shows the number of candidates sitting Physics & Chemistry in the Leaving Certificate during the period 2006–2009.
Year
LC candidates
% taking Physics & Chemistry
Physics & Chemistry candidates
Ordinary Level
Candidates
%
Higher Level
Candidates
%
2006 50955 1.1% 582 124 21.3% 458 78.7%
2007 50870 1.1% 538 146 27.1% 392 72.9%
2008 52144 1.1% 598 144 24.1% 454 75.9%
2009 54196 1.0% 519 111 21.4% 408 78.6%
Table 1: Numbers of Leaving Certificate Physics & Chemistry candidates 2006–2009 The number of candidates taking Physics & Chemistry was always small and is gradually declining with most schools now offering a greater range of science subjects. Physics & Chemistry was traditionally taken by students in small rural schools, which were unable, due to their enrolment numbers, to offer a broad range of science subjects. In recent years, the subject, particularly at Ordinary Level, is taken by students in a number of inner-city schools, even though these schools usually offer a broad range of Leaving Certificate science subjects.
This report should be read in conjunction with the examination paper and the published marking scheme. These are available on the State Examination Commission’s website: www.examinations.ie
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2. Ordinary Level
2.1 Introduction Physics and Chemistry at Ordinary Level is assessed by means of a terminal written examination of three hours duration, marked out of 400 marks. The paper is divided into two sections – Section I and Section II:
• Section I is Physics (50%) and Section II is Chemistry (50%). Candidates are required to answer three questions from six given questions in each section.
• The first question in each section (Question 1 and Question 7) consists of fifteen short items, of which eleven are to be answered.
• The last question (Question 6) in Section I consists of four parts – two parts are to be answered.
• The last question (Question 12) in Section II consists of three parts – two parts are to be answered.
• There is no compulsory question on the examination paper.
• Appropriate data are provided in the relevant questions.
2.2 Performance of Candidates As the number of candidates is small, any statistical analysis of the data must be interpreted with caution. Table 2 shows the percentages of candidates achieving each grade in the Ordinary Level Physics & Chemistry examination in the period 2006–2009.
Year Total A B C ABC D E F NG EFNG
2006 124 4.0 20.2 30.7 54.9 26.6 11.3 6.5 0.8 18.6
2007 146 4.8 20.5 26.0 51.3 25.3 8.9 11.0 3.4 23.3
2008 144 4.2 16.0 28.4 48.6 27.0 11.1 9.0 4.2 24.3
2009 111 5.4 12.6 26.1 44.1 29.7 11.7 10.8 3.6 26.1
Table 2: Percentage of candidates achieving each grade in Ordinary Level Physics & Chemistry 2006–2009
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Table 3 shows the average percentage mark per question and the response rate in individual questions. The Rank Order is in relation to each of the two sections on the paper. The Response Rate is given as the percentage of candidates attempting each question in each section. The data in Table 3 are based on a random sample of 20 scripts, approximately 18% of the total Ordinary Level cohort. Section Question Topic Average
% mark Rank Order
Response Rate (%)
Rank Order
I
Physics
1 General 52 3 95 1
2 Work & Energy 39 5 65 2
3 Reflection of Light 53 2 50 5
4 Behaviour of Gases 36 6 60 3
5 Electricity 41 4 25 6
6 General 59 1 55 4
II
Chemistry
7 General 47 3 100 1
8 Atomic Theory 50 2 60 2
9 Redox 53 1 45 5
10 Titration 45 4 55 3
11 Organic Chemistry 27 6 5 6
12 General 36 5 54 4
Table 3: Performance of candidates and response rates in Ordinary Level Physics & Chemistry 2009
• 45% of the candidates attempted more than the required number of questions. • 85% of candidates attempted three questions in each section. • 15% of candidates who were awarded grade E, F or NG did not attempt the required
number of questions.
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2.3 Analysis of Candidate Performance The standard of answering in the 2009 Ordinary Level Physics and Chemistry examination was somewhat poorer than in recent years.
Section I – Physics In this section questions 1, 2 and 4 were the most popular, while questions 1, 3 and 6 were the best answered.
Question 1 Average Mark 52% Response Rate 95% This was the second most popular question on the paper.
(a) A cyclist moves at a constant speed of 10 m s–1. What distance does the cyclist travel in 5 minutes?
Attempted by most candidates. The most common error was using the wrong formula.
(b) What is meant by acceleration?
Well answered.
(c) In the equation 2rGMg = , what does G represent?
‘Gravity’ was a common answer, very few candidates referred to G as a ‘constant’.
(d) Give one example of a thermometric property.
Well answered.
(e) Figure 1 shows rays of light passing through a lens and meeting at the focus F.
What type of lens is shown?
Well answered.
(f) How would you show the dispersion of white light?
Well answered.
(g) Figure 2 shows a waveform. What name is given to the number of waves passing a fixed point every second?
Very few candidates answered this correctly; ‘wavelength’ was the most common wrong answer.
(h) What happens when light waves with the same wavelength meet?
Poorly answered.
(i) Copy and complete the following statement of Coulomb’s law:
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Most candidates had ‘distance’ correct.
(j) Calculate the number of units (kW h) used by a 3 kW electric immersion heater in 30 minutes.
The most common error was failing to convert minutes to seconds.
(k) What is the purpose of a fuse in a 3-pin plug?
Well answered.
(l) Figure 3 shows an energy efficient lamp with a power rating of 11 W when connected to a 230 V source. Calculate the current drawn by the lamp.
Calculations were frequently incorrect.
(m) State the principle on which the moving-coil galvanometer is based.
Very few candidates attempted this part.
(n) Iodine–131 has a half-life of 8 days. What fraction of a sample of iodine–131 remains after 16 days?
Very few candidates got this right; many candidates divided the atomic mass by 2.
(o) What type of nuclear reaction occurs in a nuclear power plant?
Well answered.
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Question 2 Average Mark 39% Response Rate 65% This was a popular question but it was not well answered.
• State the principle of conservation of energy. Well known.
• Define (i) weight, (ii) work. Give the unit of work. Both definitions and unit were well answered.
• Figure 4 shows a weightlifter who has lifted a barbell of mass 50 kg to a height of
1.6 m above the ground. The work done by the weightlifter is stored as energy in the barbell. Name this form of energy. Very few candidates were able to name the correct form of energy.
• Explain why no work is done by the weightlifter on the barbell if he holds it steady.
The better candidates had this correct. • Calculate: (iii) the weight of the barbell (iv) the work done in lifting the barbell
(v) the energy lost by the weightlifter in lifting the barbell. Very few candidates calculated the weight correctly, part (iv) was usually correct; part (v) was very poorly answered.
• The weightlifter then drops the barbell. State the energy change which occurs as the
barbell is falling. Well answered.
• Calculate the velocity of the barbell as it strikes the ground.
Very few candidates got this correct.
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Question 3 Average Mark 53% Response Rate 50% This question was not popular but was well answered. • What is meant by the reflection of light? A plane mirror is a flat highly reflective
surface. Give one use of a plane mirror.
Well answered. • A law of reflection of light states that the angle of incidence equals the angle of
reflection. Describe an experiment to verify this law using a plane mirror. Give one precaution to ensure a more accurate result.
Most candidates scored well in this part of the question. • Figure 5 shows a pin O placed 8 cm in front of a concave mirror of focal
length 4 cm. Draw a ray diagram to show the formation of the image.
Many candidates had only one correct ray. • Find the distance of the image from the concave mirror.
Not well answered. • Give two differences between this image formed in the concave mirror with an image
formed in a plane mirror.
Many candidates had only one correct difference. • Give one use of a concave mirror.
Many candidates gave the use for a convex mirror.
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Question 4 Average Mark 36% Response Rate 60% This question was popular but was not well answered. part (a). • Water is boiling in a kettle. What is the temperature of boiling water when using
(i) the Celsius scale, (ii) the Kelvin scale? Part (i) was well answered, while part (ii) was seldom correct.
• Copy and complete the statement of Charles’ law:
‘Pressure’ and ‘volume’ were usually in the right sequence. • Figure 6 shows a balloon containing 200 cm3 of helium gas at 280 K. The balloon is
then placed in a flask of liquid nitrogen at a temperature of 70 K. Calculate the new volume of the balloon when it is in the flask.
Many candidates did not know the correct formula. part (b). • State two assumptions of the kinetic theory of gases.
Well answered. • What is Brownian motion?
Well answered. • Describe an experiment to show Brownian motion.
The better candidates answered this part well.
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Question 5 Average Mark 41% Response Rate 25% This question was the least popular in Section I and was not well answered. • A straight wire carrying a current is surrounded by a magnetic field. How can this
magnetic field be detected? Sketch the shape of this magnetic field.
Candidates often had the detection correct but had the shape of the magnetic field incorrect.
• Name one other effect of an electric current.
‘Heating’ was the most common answer. • Figure 7 shows a circuit with a 10 Ω resistor and a 5 Ω resistor in series connected to
a battery. The current in the circuit is 0.4 A. Calculate: (i) the effective resistance of the two resistors (ii) the voltage (potential difference) across the 5 Ω resistor. Most candidates had part (i) correct, while part (ii) was rarely correct – 0.4 A was the most common incorrect answer.
• A transformer is used to change a.c. voltages. What does a. c. represent?
Very well answered. • Name one device which uses a transformer.
Well answered, with ‘mobile phone charger’ being the most common answer. • Why does an electricity supply company transmit electrical power at high voltages?
Only the better candidate referred to ‘energy losses’. • Figure 8 shows a transformer. Identify the parts labelled A, B and C.
Well answered. • Part A is connected to a 300 V a.c. supply and has 600 turns. If the output voltage is
1200 V, calculate the number of turns needed on part B.
Poorly answered.
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Question 6 Average Mark 59% Response Rate 55% This was the best answered question overall. Parts (a) and (d) were the most popular parts.
part (a) • Define momentum. State the principle of conservation of momentum.
Both were well answered. • In Figure 9, a bowling ball of mass 4 kg moves with a velocity of 8 m s–1 on a
smooth bowling alley. The ball strikes a stationary bowling pin of mass 1.5 kg. After the collision they both move in the same direction and the bowling ball moves with a velocity of 3 m s–1. Calculate: (i) the momentum of the bowling ball before the collision (ii) the momentum of the bowling pin after the collision.
Part (i) was usually correct, but the calculations in part (ii) were usually mixed up.
part (b) • Ultraviolet radiation is a region of the electromagnetic spectrum. Name two other
regions of the electromagnetic spectrum.
Well answered. • Give one property common to all regions of the electromagnetic spectrum.
Well answered. • When ultraviolet radiation is shone on the zinc, the gold leaf drops. Name this
phenomenon. Explain why the leaf drops.
Poorly answered.
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part (c): • Figure 11 shows the two charged plates of a parallel plate capacitor.
Copy the diagram and show the direction of the electric field between the plates.
Poorly answered.
• State how the capacitance of the capacitor will change if: (i) the distance between the
plates is increased, (ii) the common area between the plates is decreased.
Part (i) was usually correct, but most candidates gave ‘increase’ as an incorrect answer to part (ii).
• Figure 12 shows how two capacitors can be combined with a battery. In diagram A
the capacitors are arranged in series. How are the capacitors arranged in diagram B?
Well answered. • Calculate the effective capacitance of the two 10 µF capacitors (i) in diagram A,
(ii) in diagram B.
Many candidates had the correct answers but in reverse order.
part (d): • What is radioactivity?
Well answered. • In beta radiation, negatively charged particles are emitted. Which type of nuclear
radiation emits positively charged particles?
Not always correct. • List two uses of radioactive substances. Give two precautions when using
radioactive substances.
Candidates scored very well in this part of the question.
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Section II – Chemistry In this section, questions 7, 8 and 10 were the most popular questions, while questions 7, 8 and 9 were the best answered questions. Question 7 Average Mark 47% Response Rate 100% This was the most popular question overall.
(a) Sketch an s-orbital.
Well answered, the shape of the p-orbital was a common incorrect answer.
(b) How many (i) protons, (ii) neutrons, are there in Be94 ?
This was poorly answered with candidates in many cases giving incorrect combinations.
(c) Define electronegativity.
Well answered.
(d) Copy and complete the statement on isotopes:
‘electrons’ appeared in both parts, some candidates ignored the statement and gave the definition in terms of atomic number and mass number.
(e) Give one example of an ionic compound.
Very poorly answered; ‘water’ was a common incorrect answer.
(f) The relative molecular mass of hydrogen gas (H2) is 2. Calculate the number of molecules in 18 g of hydrogen gas.
Most candidates scored half marks for this part.
(g) Calculate the percentage of oxygen by mass in calcium carbonate (CaCO3).
Well answered, a few candidates multiplied the values for Mr.
(h) Define electrolysis
Most candidates answered this with an example.
(i) What is the pH of a 0.05 M solution of hydrochloric acid (HCl)?
Very well answered.
(j) Which one of the following oxides is acidic? MgO CO NO2
Poor answered, most candidates guessed the answer.
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(k) Give one characteristic property common to transition elements. Well answered.
(l) Copy, complete and balance the following reaction:
Most candidates were unable to complete the reaction or balance it correctly.
(m) List the following elements in order of decreasing chemical activity:
copper, calcium, iron Very poorly answered, many candidates had only two of them in the correct order.
(n) What is a hydrocarbon?
Well answered.
(o) Why is the compound shown in Figure 13 classified as aromatic?
This was poorly answered. Many candidates were unable to identify the benzene ring as the reason for the compound being aromatic.
Na2SO3 + HCl NaCl + _____ + H2O
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Question 8 Average Mark 50% Response Rate 60% This question was popular and was well answered. • A neutron is a subatomic particle found in the nucleus of an atom. Name one other
particle found in the nucleus of an atom. Give one difference between these two particles.
Very well answered. • Give the electronic (s, p) configuration of an atom of chlorine.
Very well answered. • State the type of bond formed when two atoms of chlorine combine.
Candidates frequently confused ‘ionic’ and ‘covalent’ bonding throughout this question.
• Explain, with the aid of a diagram, how this bond is formed.
Most candidates made a reasonable attempt at this part. • Give one property of a substance with this type of bond.
Many candidates didn’t give any property. • Fluorine and chlorine are elements found in the same group of the periodic table.
Explain the underlined terms.
This part was poorly answered with many candidates not answering it. • Name one other element in this group.
Very well answered by all candidates. • What is meant by ionisation energy? Explain why the first ionisation energies
decrease down a group.
Candidates showed a good knowledge of this topic.
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Question 9 Average Mark 53% Response Rate 45% This question was not popular but was the best answered question in Section II.
Part (a) • In a redox reaction, oxidation and reduction occur. Explain the underlined words in
terms of electron transfer.
Very well answered. • Identify the substance oxidised in the following reaction: Mg + F2 MgF2
Poorly answered. • Copy and complete the following reaction: CuO + H2 ___ + ___
Identify the oxidising agent in this reaction.
Candidates were able to complete the equation but many candidates were not able to name the oxidising agent.
Part (b) • Using the Brønsted-Lowry theory, Define (i) an acid, (ii) a base.
What is a meant by a strong acid?
All parts were well answered. • Identify two acids and two bases in the following reaction:
Well answered by most candidates, but a few candidates had them in reverse order. • Give one example of an acid-base pair in this reaction.
Well answered.
NH3 + H2O NH4+ + OH
–
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Question 10 Average Mark 45% Response Rate 55% This question was popular but was not well answered. • Figure 14 shows glassware used during a titration to find the concentration of a
potassium hydroxide (KOH) solution
Both definitions were poorly answered.
. Explain the underlined terms.
• Identify the pieces of glassware labelled A, B and C.
Well known. • Give one safety precaution required when filling A.
While most candidates gave a precaution, it wasn’t always related to safety. • State one precaution required when reading the level of liquid in B.
Well answered. • Why is an indicator used during a titration?
Well answered. • Explain why deionised water is added to C during the titration.
Many candidates had a difficulty in explaining the role of deionised water. • It was found that 21.5 cm3 of 1.5 M hydrochloric acid (HCl) solution reacted with 25
cm3 of the potassium hydroxide (KOH) solution. Copy and complete the equation for the reaction that takes place in this titration:
Many candidates were unable to complete the equation. • Calculate the molarity of the potassium hydroxide solution.
Poorly answered. • Name the salt produced in this experiment.
Only a few candidates had this correct. • Explain how a sample of the salt can be separated from the solution.
Only a small number of candidates were able to answer this correctly.
HCl + KOH ____ + ____
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Question 11 Average Mark 27% Response Rate 5% This was the least popular question overall and the most poorly answered. As only a few candidates attempted this question, it is not possible to comment on the standard of answering in individual parts. Question 12 Average Mark 36% Response Rate 55% This question was neither popular nor well answered. part (a) • Define a mole of a substance.
Very poorly answered. • Describe the appearance of carbon and oxygen at room temperature.
Most candidates tried to give a single description for the two elements. • Carbon and oxygen react together to form carbon dioxide as follows: C + O2 CO2
If 36 g of carbon were used in this reaction, calculate: (i) the number of moles of carbon used (ii) the mass of carbon dioxide produced.
Very poorly answered. • What environmental impact is caused by carbon dioxide in the atmosphere?
Well answered. • Name one major source that releases carbon dioxide into the atmosphere.
Well answered. part (b) • Figure 15 shows oxygen (O2) gas being prepared. Name the liquid A and the solid B.
Many candidates named the chemicals for the preparation of CO2 instead of O2. • What is the purpose of solid B?
Well answered. • Describe a test for the presence of oxygen.
Well answered. • Give one commercial use for oxygen gas.
Well answered.
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part (c) • Figure 16 shows three molecular shapes from the electron pair repulsion theory.
Name each of the molecular shapes A, B and C.
A and C were usually correct, but most candidates did not have B correct. • Give the bond angle (i) in molecule A; (ii) in molecule B.
A was generally correct, but B was usually wrong. • What is the molecular shape of methane (CH4)?
Only a small number of candidates were able to answer this correctly. • Explain the molecular shape of H2O using the electron pair repulsion theory.
Very few candidates were able to explain this
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2.4 Conclusions
• The examination paper was well received by teacher representative organisations, teachers and examiners. The choice of questions on the paper gave candidates an opportunity to apply their knowledge and understanding of the subject.
• The structure of the paper enabled candidates to select their questions and chose an appropriate range and options within the questions. Candidates had adequate time to complete the required number of questions and many candidates attempted extra questions.
• It is encouraging to see that candidates are doing more experimental work in the classroom. This is apparent from their experimental descriptions.
• Diagrams were generally used by candidates to support written answers. These were usually well drawn and labelled except for the ray diagram in question 3.
• At Ordinary Level the standard was lower than in recent years, and very few candidates attempted extra questions. Where candidates did not achieve a grade D or higher, many did not attempt the required number of questions. The more able candidates attempted more than three questions in each section.
• Parts of questions which were particularly well answered were question 1 (e), (k), (o); question 4 (b); question 6 (d); question 7 (i), (k), (n); question 8; question 9 (b); question 12 (c).
• Definitions and laws were answered satisfactorily. While candidates seemed to know the laws, their understanding of applications of the laws was sometimes poor.
• Candidates favoured questions on mechanics and atomic theory, with very few candidates attempting the organic chemistry question.
• In the Chemistry section, candidates had difficulty in the writing of balanced chemical equations – this was very obvious in question 7 (l), question 9 (a) and question 10.
• A number of candidates showed a lack of detailed knowledge and accuracy in their answering.
• Where candidates did poorly, there were three major causes: not answering enough questions, not displaying a clear understanding of the subject; and not calculating correctly.
• Units of measurement were often omitted or incorrect.
• There was a marked tendency for candidates to avoid questions on electricity and on organic chemistry.
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2.5 Recommendations to Teachers and Students
It is recommended that teachers
• provide opportunities for their students to study all sections of the syllabus
• achieve a balanced coverage of both areas, Physics and Chemistry, so that candidates can attempt a broader range of questions from each section of the examination paper
• ensure that plenty of experiments and demonstrations are undertaken to make the subject more engaging for the students
• encourage students to experience a wide variety of practical and relevant situations in which they can apply their knowledge of the principles and concepts of Physics and Chemistry.
It is recommended that students
• study all sections of the syllabus and answer the required number of questions in the examination
• express their understanding of scientific concepts in language that is clear, concise and correct
• improve their basic mathematical computational skills
• improve their understanding of basic Chemistry by balancing equations, and writing chemical formulae and chemical equations.
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3. Higher Level
3.1 Introduction Physics and Chemistry at Higher Level is assessed by means of a terminal written examination of three hours duration and is marked out of 400 marks. The paper is divided into two sections – Section I and Section II:
• Section I is Physics (50%) and Section II is Chemistry (50%). Candidates are required to answer three questions from six given questions in each section.
• The first question in each section (Question 1 and Question 7) consists of fifteen short items, of which eleven are to be answered.
• The last question (Question 6) in Section I consists of four parts – two parts are to be answered.
• The last question (Question 12) in Section II consists of four parts – three parts are to be answered.
• There is no compulsory question on the examination paper.
• Appropriate data are provided in the relevant questions.
3.2 Performance of Candidates Table 4 shows the percentages of candidates achieving each grade in the Higher Level Physics & Chemistry examination in the period 2006–2009.
Year Total A B C ABC D E F NG EFNG
2006 458 13.3 22.9 27.9 64.1 22.2 9.4 3.9 0.2 13.5
2007 392 23.0 25.5 25.7 74.2 16.2 6.1 3.1 0.5 9.7
2008 454 26.0 26.4 20.5 72.9 14.0 7.3 4.4 1.3 13.0
2009 408 17.2 26.7 26.0 69.9 19.6 5.9 3.7 1.0 10.6
Table 4: Percentage of candidates achieving each grade in Higher Level Physics & Chemistry 2006–2009
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Table 5 shows the average percentage mark per question and the response rate in individual questions. The Rank Order is in relation to each of the two sections on the paper. The Response Rate is given as the percentage of candidates attempting each question in each section. Data in Table 5 are based on a random sample of 20 scripts, approximately 5% of the total higher level cohort. Section Question Topic Average
% mark Rank Order
Response Rate (%)
Rank Order
I
1 General 62 2 88 1
2 Newton’s 2nd Law 57 5 85 2
3 Refraction of Light 66 1 60 4
4 Behaviour of Gases 59 3 58 5
5 Electricity 30 6 15 6
6 General 58 4 80 3
II
7 General 64 2 93 2
8 Atomic Theory 42 6 73 3
9 Titration 63 3 98 1
10 Redox 51 5 45 5
11 Organic Chemistry 71 1 10 6
12 General 60 4 68 4
Table 5: Performance of candidates and response rates in Higher Level Physics & Chemistry 2009
• Most candidates attempted a minimum of three questions for each section. • Most candidates attempted more than the required number of questions, with
77.5% of candidates attempting between one and five additional questions.
• Of the candidates who achieved an A grade, 80% attempted additional questions.
This report should be read in conjunction with the examination paper and the published marking scheme. These are available on the State Examination Commission’s website: www.examinations.ie
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3.3 Analysis of Candidate Performance
Section I – Physics In this section Questions 1, 2 and 6 were the most popular and Questions 1 and 3 were the best answered. The average mark of 30% in Question 5 was significantly below the overall average mark of 57%.
Question 1 Average Mark 62% Response Rate 88% The most popular question in this section and was reasonably well answered. Candidates showed good course coverage, knowledge of definitions and were able, in most cases, to attempt the required number of items and, often, additional items.
(a) Define work.
The definition was not well answered.
(b) State Newton’s law of gravitation.
Statement of Newton’s law of gravitation was well answered.
(c) Distinguish between a vector and a scalar.
Vectors and scalars were often answered in reverse order or incompletely.
(d) When an object is placed 3 cm in front of a concave mirror, a virtual image is formed 9 cm from the mirror as shown in Figure 1. What is the focal length of the mirror? Candidates confused the sign convention for a virtual image and also confused the arithmetic of fractions.
(e) Give one difference between a transverse wave and a longitudinal wave.
Candidates were generally able to distinguish between transverse and longitudinal waves.
(f) Give two properties of infrared radiation.
Few candidates were able to give properties of infrared radiation.
(g) What is the photoelectric effect?
The photoelectric effect was well defined.
(h) Write an expression that defines temperature on the Celsius scale.
Most candidates gave the definition of the temperature correctly.
(i) What is Brownian movement?
Most candidates explained what Brownian movement is but some only provided an example and only merited half marks.
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(j) F is the force between the two point charges. What is the force between the charges in terms of F when the distance between their centres is halved?
There were few correct answers about the effect on the size of the electrostatic force when halving the distance between the charges.
(k) State Ohm’s law.
Many correct responses to the definition.
(l) What is electromagnetic induction?
This item on electromagnetic induction was poorly answered and not attempted as often as some of the others.
(m) Figure 2 shows a transformer that has 5 turns in the secondary coil and 200 turns in the primary coil. Calculate the output voltage when the primary coil is connected to the 230 V mains supply.
The problem on transformers was very well answered.
(n) Why do alpha particles have a shorter range in air than beta particles?
Poorly answered. Candidates often re-phrased the question in terms of the relative penetrating powers of alpha and beta particles, but failed to refer to relative size, mass or charge.
(o) A sample of radioactive iodine–131 had one sixteenth of its original activity after 32 days. What is the half-life of iodine–131?
Poorly answered. A number of candidates tried to use the figure 131 in a calculation.
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Question 2 Average Mark 57% Response Rate 85%
A popular question with many parts well answered.
• Define acceleration. Candidates were able to define acceleration correctly.
• State Newton’s second law of motion. Candidates were able to state Newton’s second law correctly.
• Derive the relationship force = mass × acceleration from Newton’s second law.
Most candidates had difficulty with the derivation.
• In an experiment to verify Newton’s second law, a force F was applied to a trolley that moves over a smooth horizontal surface as shown in Figure 3. The acceleration a of the trolley was measured. This procedure was repeated a number of times for different values of the applied force, keeping the mass accelerated constant each time. The values of F and the corresponding vales of a are given in the table. Describe how the acceleration of the trolley was measured.
Candidates were able to describe a method to measure the acceleration of the trolley but many answers were very brief and incomplete.
• Draw a suitable graph on graph paper to show the relationship between the applied force F and the acceleration a.
Many graphs were well drawn. Some candidates did not label the axes and did not plot the points correctly. A number of candidates did not join the points with a single straight line.
• From your graph, determine the mass accelerated. In general the graph and associated work was handled well by the candidates. However, several candidates did not use points on the line to get the slope and hence the mass. A few candidates calculated mass by averaging the data in the table. Many candidates did not use the graph to get the acceleration when the force was 5N.
• Calculate how far the trolley would travel in 0.5 s, starting from rest, if the force applied is 5 N.
Some candidates substituted force for a in the formulae v = u + at and s = ut + ½at2.
• The experiment was rearranged, this time applying a constant force to a series of different masses and measuring the corresponding accelerations. What relationship between mass and acceleration was established?
Most candidates were unable to deduce the correct relationship between mass and acceleration when force was held constant.
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Question 3 Average Mark 66% Response Rate 60%
This was not a popular question but was well answered by those who attempted it.
• What is refraction of light?
Some candidates had trouble with definition of refractive index. Very few candidates explained i and r.
• When does refraction not occur as a ray of light travels from one medium into
another?
Poorly answered.
• Define (i) refractive index, (ii) critical angle.
Some candidates had trouble with definition of critical angle.
• Describe an experiment to measure the refractive index of glass
The experiment was well described.
• Figure 4 shows a ray travelling from water to air from an underwater light source.
Calculate (i) the refractive index of water; (ii) the critical angle of water; (iii) the speed of light as it travels through water.
Some candidates had difficulties with the calculations, especially the critical angle and speed of light parts.
• Draw a diagram to show what happens when a ray from the underwater light source
strikes the water-air surface at an angle that exceeds the critical angle.
Many diagrams of total internal reflection did not show the angle of incidence equal to the angle of reflection.
• Name this phenomenon and give one application of it.
Most candidates were able to name the phenomenon and give an application of it.
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Question 4 Average Mark 59% Response Rate 58%
This was not one of the most popular questions but was reasonably well answered by those who attempted it.
part (a)
• Boyle’s law describes the relationship between the volume and the pressure of a fixed mass of gas at constant temperature. The kinetic theory of gases describes the behaviour of the molecules of an ideal gas. Describe, with the aid of a labelled diagram, an experiment to verify Boyle’s law
The experiment was well described by most candidates. Some diagrams were poorly drawn and labelled. Some candidates failed to explain how their readings were used to verify Boyle’s law.
part (b)
• What is an ideal gas? This question was well answered.
• State two assumptions of the kinetic theory of gases. Well answered.
• How does an increase in temperature affect the behaviour of molecules in an ideal gas? Well answered.
part (c)
• Explain how Boyle’s law is consistent with the equation of state of an ideal gas, PV = nRT. Candidates had difficulty in explaining this.
part (d)
• Each bubble of air released from an aerator placed at the bottom of a lake has a volume 1.2 cm3 when it reaches the surface where the atmospheric pressure is 1.01 × 105 Pa. The temperature of the lake is 4 ºC throughout.
Calculate (i) the pressure at the bottom of the lake if the bubbles expand to twice their original size as they rise through the water; (ii) the number of moles of gas in each bubble of air.
Candidates also had difficulty with the calculations. While the pressure at the bottom of the lake could have been easily worked out without calculation, many candidates employed the general gas law, incorrectly, to get a smaller pressure than at the surface. Most candidates failed to convert temperature to Kelvin and volume
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to cubic metres. Another common error was where candidates combined volume from the top of the lake with pressure at the bottom and vice versa.
part (e)
• Explain the term thermometric property. Name the thermometer that uses the pressure of a fixed mass of gas as its thermometric property.
The thermometric property and constant volume gas thermometer parts of the question were generally well answered.
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Question 5 Average Mark 30% Response Rate 15%
This was the least popular question in Section I. It was the most poorly answered question overall and the only question with an average mark below the pass mark of 40%. As the response rate was low and the standard of answering was poor, it was not possible to undertake a proper review of the candidates’ answers.
• Define (i) electric current, (ii) the ampere, the SI unit of electric current. • Figure 5 shows a moving coil galvanometer. Explain how it measures a small
electric current. How is a moving coil galvanometer modified to measure larger currents?
• Describe an experiment to demonstrate the heating effect of an electric current.
• Why does an electricity supply company (i) transmit electricity over long distances at high voltage; (ii) use alternating current instead of direct current?
• A power station supplies electrical energy at a voltage of 10 kV and at a rate of
2 MW to a factory. The cables connecting the power station and the factory have a resistance of 9.5 Ω. Calculate (i) the current flowing in the cables; (ii) the power ‘lost’ in the cables due to heating.
• If the supply voltage is maintained at 10 kV, how can power losses in the cables be
reduced?
The definitions were the best-answered parts with many candidates giving a good definition of the ampere.
All other parts were poorly attempted. Candidates showed little knowledge or understanding of the subject matter and little familiarity with or practice using the formulae required for the calculations.
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Question 6 Average Mark 58% Response Rate 80%
A popular question with a good average mark. Parts (a) and (c) were well answered. Part (b) was the least popular.
part (a)
• Define kinetic energy. • State the principle of conservation of momentum.
Candidates were able to define kinetic energy and state the principle of conservation of momentum.
• A cannon of mass 1000 kg containing a cannonball of mass 20 kg was at rest on a
smooth horizontal surface as shown in Figure 6. The cannonball was fired with an initial horizontal velocity of 400 m s–1. Calculate (i) the recoil velocity of the cannon;(ii) the kinetic energy of the cannon as it recoils. Why does the cannon recoil?
Many candidates did not substitute masses and the given velocity correctly into the conservation of momentum formula. The kinetic energy calculation was usually well answered. Only a few candidates were able to explain why the cannon recoiled.
part (b)
• Diffraction and interference occur when a narrow beam of monochromatic light
Explain the underlined terms. How does this experiment contribute to our understanding of the nature of light? Calculate the wavelength of the light.
passes though a pair of narrow slits, whose separation is 0.5 mm, and then strikes a screen 1.2 m away. A pattern of bright and dark images is formed on the screen as shown in Figure 7. The distance from the fifth bright image to the central bright image is 7.1 mm.
The underlined terms were well answered. However, only a few candidates were able to calculate the wavelength of the light.
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part (c)
This part was well answered. Candidates had less difficulty with this topic than they had with current electricity in Question 5.
• Define capacitance.
• Describe an experiment to investigate how the capacitance of a parallel plate capacitor depends on the separation between the plates. In the experiment, many candidates were not able to explain the relationship between the divergence of the leaves, potential difference and capacitance.
• Figure 8 shows a 6 V battery connected to an arrangement of capacitors. • Calculate (i) the effective capacitance of the circuit; (ii) the charge stored in the
circuit when the switch is closed.
In the calculation, some candidates reversed the formulae for series and parallel arrangements of capacitors and some candidates had difficulty with the arithmetic of fractions.
part (d)
• Determine the value of A, the value of Z and the symbol of the element represented by X in the following nuclear fission reaction.
235
92 U + 1
0 n → A
Z X + 9036 Kr + 2
1
0 n + energy
Well answered.
• Explain (i) why a large quantity of energy is released in this reaction; (ii) why fission of uranium–235 may result in a chain reaction.
Poorly answered.
• Deuterium 2
1 H is an isotope of hydrogen. Write a balanced equation for the nuclear fusion reaction when two deuterium nuclei combine to produce a helium nucleus and energy. Explain why fusion only occurs at extremely high temperatures.
The equation was well answered by most candidates.
The explanation was poorly answered.
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Section II – Chemistry In this section, Questions 7 and 9 were the most popular and (apart from the least popular Question 11 on Organic Chemistry) were also the best answered.
Question 7 Average Mark 64% Response Rate 93%
This was a popular and generally well-answered question. As in Question 1 candidates showed good course coverage, knowledge of definitions and, in most cases, answered the required number of items and, often, additional items.
(a) What are isotopes?
Well answered.
(b) What do the terms E2 and f represent in the relationship E2 – E1 = hf ?
Candidates were able to identify E as an energy term and f as a frequency term, but most candidates were not able to elaborate on the significance of the subscript.
(c) Define electronegativity.
Well answered.
(d) What is the maximum number of electrons that can occupy (i) the third shell, (ii) the 3p subshell, of an atom?
Most candidates answered this well.
(e) State the number of (i) neutrons, (ii) protons in the27
13 Al3+
ion.
Most candidates answered this well.
(f) What colour change is observed when chlorine gas is bubbled through a solution of sodium iodide as shown in Figure 9?
Very few were able to give either of the required colours.
(g) Name a metallic element whose salts give a lilac colour to a Bunsen flame.
This item was well answered.
(h) Calculate the pH of a 0.2 M solution of sulfuric acid.
Many candidates did not double the molarity of the sulfuric acid to find the molarity of the H+ ion.
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(i) Name two oxides that are involved in the formation of acid rain.
Many candidates gave one correct oxide and one incorrect oxide such as water or carbon monoxide.
(j) Define the heat of formation of a compound.
Well answered but reference to standards states was sometimes omitted or replaced with the incorrect term ‘natural states’.
(k) Explain why the molecule NH3 has a dipole moment while BF3 does not.
Well answered by only some candidates.
(l) Figure 10 shows gigantic gypsum crystals discovered recently in a cave in Mexico. Calculate the percentage by mass of water of crystallisation in gypsum which has the chemical formula CaSO4 2H2O.
Many candidates incorrectly added the atomic masses to get the molecular mass of the salt but proceeded correctly thereafter.
(m) Figure 11 shows Milk of Magnesia tablets containing the active ingredient Mg(OH)2 being added to neutralise excess hydrochloric acid in the stomach. Write a balanced equation for this reaction.
Construction of balanced equation poorly handled by most candidates
(n) Name a reagent used to distinguish between an aldehyde and a ketone.
Very few attempts at this organic chemistry item and of these very few answers were correct.
(o) Draw the structures of the two compounds that have the molecular formula C4H10.
Most candidates who attempted this item were able to draw only one correct isomer of butane.
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Question 8 Average Mark 42% Response Rate 73%
This question was popular but not well answered
• Explain the term atomic orbital. Atomic orbital was usually correctly defined.
• Write the electron configuration of (i) a carbon atom, (ii) an iron atom. Well answered.
(a) Diamond and graphite are crystalline solids of carbon.
• Explain in terms of bonding why diamond and graphite differ (i) in their hardness, (ii) in their ability to conduct electricity.
Very few candidates could answer this part satisfactorily. Comments on the structures of these two allotropes were often incorrect or partially incorrect and were not developed sufficiently. Outline diagrams showing tetrahedral arrangements and planar arrangements of carbon atoms were insufficient without an explanation.
(b) Iron is a transition metal. • How is a transition element identified from its electron configuration? State
two characteristic properties of transition metals. The metallic crystalline structure of iron is shown in Figure 12. Describe the bonding in a metallic crystal. The electron configuration of iron presented difficulty to some and few were able to state how a transition element is identified from its electron configuration.
Very few candidates were able to give the required description of bonding in metallic crystals.
(c) What type of bond exists in a water molecule?
Many candidates stated that the bonding in a water molecule is hydrogen bonding.
• State the shape of a water molecule and explain, using the electron pair repulsion theory, how this shape arises. What forces hold the water molecules together in an ice crystal? What type of crystal lattice is formed in ice?
Answers to the questions about the forces holding water molecules together in ice and the type of crystal lattice in ice as well as the answers to earlier parts of question 8 suggest that candidates were familiar with the vocabulary associated with bonding and crystal structure but were unable to apply their knowledge to particular molecules or crystals.
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Question 9 Average Mark 63% Response Rate 98%
This was the most popular question on the paper. It was also well answered.
• Define (i) a strong acid, (ii) a conjugate pair, in terms of Brønsted-Lowry theory. Many candidates stated that a Brønsted-Lowry acid was ‘fully dissociated in solution’ but did not refer to ‘good proton donation’.
• State the conjugate base of the hydrogen sulfate ion HSO4– and the conjugate acid of
ammonia NH3.
Many candidates were unable to give the conjugate base and conjugate acid required and many added (or subtracted) H instead of H+ or were otherwise incorrect with the charges.
• Describe how a burette was rinsed and then filled with the sulfuric acid solution. Well answered.
• Explain why methyl orange is a suitable indicator for this titration. Many candidates stated that the suitability of methyl orange as an indicator was based on the fact that sulfuric acid is a strong acid.
• What colour change is observed at the end point in this titration?
Well answered.
• (i) Why are the sides of the conical flask washed down during a titration? (ii) Why is deionised water used in washing down the sides of the conical flask? (iii) Why is the conical flask placed on a white tile during the titration?
All parts were answered well.
• Ammonium hydroxide is a solution of ammonia gas in water. To determine the concentration of an ammonium hydroxide solution, it was titrated against a standard solution of sulfuric acid. The balanced equation for the titration reaction is
2NH4OH + H2SO4 → (NH4)2SO4 + 2H2O One rough and two accurate titrations were carried out. On average 18.6 cm3 of 0.12 M sulfuric acid solution was required to neutralise 20 cm3 samples of the ammonium hydroxide solution.
Calculate:(i) the molarity of the ammonium hydroxide solution; (ii) the concentration of the ammonium hydroxide solution in grams per litre (dm3); (iii) the mass of ammonia gas dissolved in 500 cm3 of the solution.
Some candidates did not use the relevant titration formula in their calculations.
Very few candidates were successful in part (iii).
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Question 10 Average Mark 51% Response Rate 45%
One of the less popular and less well-answered questions.
• Define in terms of electron transfer (i) oxidation, (ii) oxidising reagent. Well answered.
• Write a balanced equation for the reaction that occurs between calcium and warm water. Identify the substance oxidised and the oxidising reagent in this reaction. Not well answered.
• Place the following metals in order of increasing difficulty of oxidation. zinc calcium copper aluminium
The order of the metals was often reversed.
• Which of these metals can be found free in nature? Well answered.
• Why is iron resistant to corrosion when it is galvanised with zinc? Well answered.
• Describe what is observed when (i) aluminium is placed in copper(II) sulfate solution; (ii) copper is placed in dilute sulfuric acid; (iii) when 1.27 g of copper is added to excess concentrated sulfuric acid, the copper is oxidised.
Poorly answered
• Calculate (i) he number of moles of copper oxidised; (ii) the mass of copper(II) sulfate produced; (iii) the volume of sulfur dioxide gas produced at STP; (iv) the number of molecules of water formed.
The stoichiometric calculations were usually well answered.
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Question 11 Average Mark 71% Response Rate 10.0%
The least popular question on the paper – but those who attempted it scored highly – it also had the highest average mark.
As only a few candidates attempted this question, it is not possible to comment on the standard of answering in individual parts.
• Define (i) unsaturated compound, (ii) functional group. Answer the questions below with reference to compounds X, Y, Z and W in the reaction scheme shown in Figure 13.
(a) Name the compounds X, Y and Z.
(b) Name the homologous series to which compound Z belongs.
(c) Explain why compound Y and compound Z are soluble in water.
(d) Name the inorganic reagent used in the conversion of compound Y to compound X. (e) What is observed when compound X is bubbled through acidified potassium
permanganate? What type of reaction occurs? Write a balanced equation for the reaction that occurs when bromine is added to X.
(f) What type of reaction is involved in the conversion of compound Y to compound Z? Identify the reagents required for this conversion.
(g) Compounds Y and Z react together in the presence of sulfuric acid to form the ester W. Name the ester W. Draw the structure of the ester functional group.
W
X Y Z CH2CH2 CH3CH2OH CH3COOH
Figure 13
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Question 12 Average Mark 60% Response Rate 68%
This question was not as popular as the corresponding question in Section I, (68% versus 80%) but it had a good average mark. Part (b) on Organic Chemistry was the least popular part. Some candidates only answered two parts, instead of three.
part (a)
Figure 14 shows molten zinc chloride being electrolysed using inert electrodes.
• Name a suitable material for the electrodes. Well answered.
• Identify electrode X. Well answered.
• Write a balanced equation for the cathode reaction. Poorly answered.
• Calculate the mass of zinc deposited when a current of 0.50 A flows for 15 minutes through the molten zinc chloride.
A common error was ignoring the double charge on the zinc ion.
part (b)
• Distinguish between an aliphatic and an aromatic organic compound
• Draw the structure of the benzene molecule and describe its bonding.
• Name the reagent and the catalyst used in the mono-bromination of benzene.
• What type of reaction is the bromination of benzene?
This part was attempted by very few and was poorly answered. Candidates who studied organic chemistry appear not to be familiar with aromatic chemistry.
part (c)
• Define the first ionisation energy of an element. Ionisation energy was well defined by many candidates.
• What is the general trend in ionisation energy values across the second period of the Periodic Table?
Explanations about trends in first ionisation energies and about higher ionisation energies were correctly given by only a few candidates. Marks were lost when candidates didn’t use the terms: shell, subshell and orbital in the correct context.
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• Explain why beryllium has a high first ionisation energy value compared to the other elements in the second period.
Reasonably well answered.
• Why is the second ionisation energy of an element always greater than the first? Well answered.
• The first, second and third ionisation energy values of beryllium, are 900 kJ mol–1, 1760 kJ mol–1 and 14,800 kJ mol–1 respectively. Explain the large increase between the second and third ionisation energy values of beryllium.
Poorly answered.
part (d)
This part was very popular and usually well answered.
• Define heat of combustion. Poorly answered.
• State Hess’s law. Well answered.
• At high temperatures, methane is converted to ethyne according to the equation:
2CH4 (g) → C2H2 (g) + 3H2 (g) Calculate the heat change for this reaction using the following heats of combustion…
Well answered with many candidates achieving full marks for their calculations.
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3.4 Conclusions
• Examiners and teacher representatives agreed that the paper was very straightforward and well balanced, with clear unambiguous and fair questions. The examination paper provided a good degree of discrimination in that the more able candidates could distinguish themselves while the average candidate had sufficient scope to achieve success.
• The structure of the paper enabled candidates to select their questions and chose an appropriate range and options within the questions. Candidates had adequate time to complete the required number of questions and many candidates attempted extra questions.
• Diagrams were generally used to support written answers, where appropriate. The diagrams were usually well-drawn and labelled and able candidates used them to complement their explanations/descriptions.
• Where the performance of candidates was poor, there were two major causes: not answering enough questions and not answering fully the questions attempted. The more able candidates attempted more than three questions in each section.
• Candidates showed a good knowledge of the experiments. The less able candidates lacked detail and many gave vague or incorrect descriptions of the experiments.
• Definitions and laws were answered satisfactorily.
• Units of measurement were often omitted or incorrect.
• There was a strong tendency for candidates to avoid questions on electricity and organic chemistry.
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3.5 Recommendations to Teachers and Students
It is recommended that teachers
• provide opportunities for their students to study all sections of the syllabus
• achieve a balanced coverage of both areas, Physics and Chemistry, so that students can attempt the required number of questions from each section of the examination paper
• ensure that plenty of experiments and demonstrations are undertaken to make the subject more engaging for students
• encourage their students to experience a wide variety of practical and relevant situations in which they can apply their knowledge of the principles and concepts of physics and chemistry.
It is recommended that students
• study all sections of the syllabus and answer the required number of questions in the examination
• optimise their marks by reviewing their first six questions before attempting additional questions
• be aware that in question 6, they need to answer two parts (33 marks each), but in question 12 they need to answer three parts (22 marks each)
• express their understanding of scientific concepts in language that is clear, concise and correct
• practise typical calculations in the Physics and in the Chemistry sections in their study and improve their basic computational skills
• improve their understanding of basic Chemistry by balancing equations, and writing chemical formulae and chemical equations
• in questions that require diagrams, they should be drawn clearly and fully labelled
• be aware of the difference between ‘clear’ and ‘colourless’ when describing the appearance of a solution.
