Exemplar Candidate Work GATEWAY SCIENCE COMBINED …

Exemplar Candidate Work

J250For first teaching in 2016

GATEWAY SCIENCE COMBINED SCIENCE A

QualificationAccredited

www.ocr.org.uk/combinedsciencea

GCSE (9-1)

J250/09 Summer 2018 examination seriesVersion 1

http://ocr.org.uk/qualifications/gcse/gcse-gateway-science-suite-combined-science-a-j250-from-2016/


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GCSE (9-1) Gateway Science Suite Combined Science A

© OCR 2018

ContentsQuestion 2 4

Question 3 4

Question 5 5

Question 10 5

Question 11 (a) 6

Question 11 (b) 7

Question 11 (c) (i) 8

Question 11 (c) (ii) 8

Question 11 (c) (iii) 9

Question 12 (a) 9

Question 12 (b) 10

Question 12 (c) (i) 10

Question 12 (c) (ii) 11

Question 13 (a) (i) (ii) 12-14

Question 13 (b) 15

Question 13 (c) 16

Question 14 (a) 16

Question 14 (b) 17

Question 14 (c) 17

Question 14 (d) (i) 18

Question 14 (d) (ii) 19

Question 15 20-21

Question 16 (a) 22

Question 16 (b) 23

Question 16 (c) 24

Question 17 (a) 25-26

Question 17 (b) 27

Question 17 (c) 27

Question 18 28

Question 19 29


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IntroductionThese exemplar answers have been chosen from the summer 2018 examination series.

OCR is open to a wide variety of approaches and all answers are considered on their merits. These exemplars, therefore, should not be seen as the only way to answer questions but do illustrate how the mark scheme has been applied.

Please always refer to the specification https://www.ocr.org.uk/qualifications/gcse/gateway-science-suite-combined-science-a-j250-from-2016/ for full details of the assessment for this qualification. These exemplar answers should also be read in conjunction with the sample assessment materials and the June 2018 Examiners’ report or Report to Centres available from Interchange https://interchange.ocr.org.uk/Home.mvc/Index

The question paper, mark scheme and any resource booklet(s) will be available on the OCR website from summer 2019. Until then, they are available on OCR Interchange (school exams officers will have a login for this and are able to set up teachers with specific logins – see the following link for further information http://www.ocr.org.uk/administration/support-and-tools/interchange/managing-user-accounts/).

It is important to note that approaches to question setting and marking will remain consistent. At the same time OCR reviews all its qualifications annually and may make small adjustments to improve the performance of its assessments. We will let you know of any substantive changes.

https://interchange.ocr.org.uk/Home.mvc/Index

https://interchange.ocr.org.uk/Home.mvc/Index

http://www.ocr.org.uk/administration/support-and-tools/interchange/managing-user-accounts/




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Question 2Exemplar 1 1 mark

Examiner commentaryCandidates often gave the incorrect response of A, which actually refers to the number of ‘electrons’ in an atom being different to the number of protons. This is incorrect. An isotope has a different number of neutrons, hence the correct response is B. This answer is a good example of a candidate eliminating the incorrect answers so arriving at the correct answer.


Examiner commentaryThis question required candidates to recall their knowledge about the periodic table, in particular group 7. They should know the trends of the group. The elements melting and boiling points increase as you go down the group so you would expect Astatine to be a solid (not a gas). The reactivity of the group increases as you go up not down the group so Astatine would be less reactive than iodine. The elements become darker as you go down the group so white is not a feasible colour to expect of Astatine. Group 7 do react with group 1 to form salts so D is the correct response.


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Examiner commentaryAlloys is perhaps an area of the specification that has not been well covered in the classroom. Candidates should know the definition of an alloy to be ‘a mixture of metals’.


Examiner commentaryCandidates need to be able to perform simple calculations in multiple choice questions. The mass of the substance can be found by multiplying the volume in dm3 by the concentration and the relative formula mass. This gives 2.0 grams, response C.


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Question 11 (a)Exemplar 1 2 marks

Examiner commentaryThe high level response shows a clear understanding of the relative strengths of bond with covalent bonds being described as stronger than the metallic bonds in iron. The type of bonding in the nanotube was correctly identified and the comparative statement of strength given.

Examiner commentaryThis response shows a lack of understanding of covalent bonding and intermolecular forces, as well as melting of a giant covalent structure and metals. The use of the phrase ‘intermolecular forces’ is a contradiction therefore zero marks.

Exemplar 2 0 marks


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Question 11 (b)Exemplar 1 2 marks

Examiner commentaryThis response has identified the delocalised electrons and the idea of movement of electrons to generate an electric current.

Examiner commentaryThe word ‘transferable’ is not equivalent to delocalised or free, so the first marking point is not given. The candidate has then gone on to talk about ‘carrying a current’. A current is the movement of electrons. This candidate has described ‘carrying’ rather than ‘moving’ electrons so no mark can be given.

Exemplar 2 0 marks


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Question 11 (ci)Exemplar 1 2 marks

Examiner commentaryFrom the table of data provided 7.9 divided by 1.6 gives a ratio of 4.9 as the number of times the density of iron compared to carbon nanotubes. Candidates may have rounded this up to 5. It is preferred that the calculation be seen.

Question 11 (cii)Exemplar 1 1 mark

Examiner commentaryCandidates could describe the packing of the atoms of iron in a solid being closer together or describe in comparison, the hollow structure of the carbon nanotubes.


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Question 11 (ciii)Exemplar 1 0 marks

Examiner commentaryCandidates were expected to compare the strength of covalent bonds to metallic bonds. This comparison should have led them to describe the strength of covalent bonds as being stronger than metallics bonds. It was essential that a comparative statement was given to gain the mark in this question and not just that covalent bonds are ‘strong’. This answer did not gain the mark because they talked about intermolecular metallic bonds not just metallic bonds so showing confusion about the bonds within the metal.

Question 12 (a)Exemplar 1 1 mark

Examiner commentaryUsing the table of information provided, the candidates were expected to pick out the correct ions for aluminium and oxide. They were then expected to put them together using the correct terminology to provide the chemical formula for aluminium oxide. Several candidates left the charges on the ions rather than removing these when constructing the formula.


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Question 12 (b)Exemplar 1 1 mark

Examiner commentaryMany candidates struggled to express their ideas clearly in this question. The formula they were given was not correctly written. The difficulty seemed to arise in expressing how to fix the problem with the formula. The correct formula was actually Mg(NO3)2 showing there should have been two NO3- ions present to balance the Mg2+ ion rather than the one NO3- ion given in the original formula. The candidates could have explained this in several ways which referred to the charges not balancing so the overall charge was zero for the compound. There was no recognition for the comment alone about the teacher being incorrect or the student being correct.

Question 12 (ci)Exemplar 1 1 mark

Examiner commentaryThe correct balancing was 6 HCl, 2 AlCl

3 and 3 H

2S. This answer shows the correct balancing.


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Question 12 (cii)Exemplar 1 1 mark

Examiner commentaryCandidates were expected to use the table of data to understand that at a room temperature of approximately 25oC the compound had surpassed both it’s melting and boiling points to become a gas.


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Question 13 (ai/aii)Exemplar 1 2 marks

Examiner commentaryThis is a perfect answer as the arrows are carefully drawn to within one small square and the direction of the arrows are correct, up for A and down for E.


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Examiner commentaryThis candidate has correctly identified the regions of the graph that represent the activation energy and the energy change, however the labels have been applied incorrectly so no mark was scored. The arrows are also double headed rather than just at the top for A and at the bottom for E.


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Examiner commentaryThis was a popular response, unfortunately showing a lack of understanding of the detail needed to use the graph to identify the activation energy and the energy change. A simple arrow towards the label of reactants, products or the peak of the graph were commonly seen.


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Examiner commentaryThis candidate has demonstrated an understanding of an exothermic reaction in terms of bonding but has not fully described the energy given out at the end of a reaction. The candidate needed to describe an exothermic reaction is due to the energy needed to break the existing bonds is less than the energy released when new bonds form. They have described the endothermic process of energy needed to break bonds but not the exothermic process of releasing energy when new bonds form. The mark is given for the idea that an exothermic reaction gives out energy or heat.

Examiner commentaryThis candidate has scored 1 mark for the idea that energy or heat is released in an exothermic reaction. They have not correctly described the exothermic process of forming new bonds. Energy is not ‘needed’ when new bonds form. The other misconception frequently seen was the poor communication when describing the endothermic process of breaking bonds.

Exemplar 2 1 mark


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Question 13 (c)Exemplar 1 2 marks

Examiner commentaryThis candidate has correctly calculated the energy needed to break the bonds and the energy released when new bonds form. They have even gone on to correctly calculate the total energy released. Unfortunately, they have removed the negative sign on the answer line that would have scored the full 3 marks. Candidates need to calculate energies and apply the correct sign to gain full marks in such questions.


Examiner commentaryThis is the correct answer but a wide variety of incorrect responses were seen here, with metal hydroxide, hydrogen and bubbles being some of the more common incorrect responses. Centres should encourage candidates to learn the general equations.


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Examiner commentaryThe use of universal indicator is to test the pH of a substance. It should be noted that other substances can be used to show if the chemical is an acid or alkali and this type of broad statement should be avoided by candidates wherever possible. This answer although not ideal was allowed so gained the mark.

Question 14 (c)Exemplar 1 1 mark

Examiner commentaryThere was a significant number of candidates that could correctly quote the concentration of hydrogen ions as either 0.1 or 1x10-1


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Question 14 (di)Exemplar 1 1 mark

Examiner commentaryThis candidate has correctly identified the range as being 3.7 and has also shown the highest and lowest values which would have also gained the mark.

If the anomalous result (8.9) was taken into consideration and the range was therefore identified as the difference between 11.0 and 12.6. This gave an answer of 1.6. This answer was also allowed.


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Question 14 (dii)Exemplar 1 2 marks

Examiner commentaryThe candidate was expected to identify that both results in the sixth column were anomalies. Both of the second results were a little on the low side. This would have been creditworthy if it had been mentioned. Results 1, 3, 4 and 5 are pretty close together and so the results are of good quality.


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Question 15Exemplar 1 5 marks

Examiner commentaryThis candidate has given a comprehensive explanation and comparison of the strong cross links in polymer C and weak intermolecular forces in polymer A. Such a clear explanation was missing from the majority of responses. Instead most candidates ignored this part of the question and only discussed the properties listed in the table and related them to the ability of the box to do the job required. This candidate has given a less detailed description of how this relates to the properties of the material to make it a good storage box.


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Examiner commentaryThis candidate has identified that polymer C will be the best for the job but has simply quoted data from the table rather than use the data to relate it to everyday properties of a good box. For example if they had discussed the relative strength and then explained that this meant it was hard to break or would hold it’s shape, or the relatively low density meant it was lightweight then a higher level would be accessible. Likewise there is no discussion of the structure and how this relates to the properties.


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Examiner commentaryThis answer has identified that the boiling point is relatively low as the molecule has weak intermolecular forces holding the molecules together so gaining one mark. ‘Easy to overcome them’ was insufficient for the second mark. To gain the second mark the answer needs to talk about the small amount of energy needed to break these intermolecular forces leading to a low boiling point.


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Examiner commentaryThis candidate has clearly shown the dot and cross symbols to score both marks. Inner electrons are not needed for the mark, neither is a linear shape (although it would be preferred).


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Question 16 (c)Exemplar 1 2 marks

Examiner commentaryThe movement of electrons was mentioned by the majority of candidates. Unfortunately the direction of the transfer of the electrons was not clarified. It was expected that the candidates would explain the metals would release the electrons that would then pass to the non-metals creating ions. Metals producing positive ions and non-metals producing negative ions. There in then an electrostatic attraction formed between the positive metal ion and the negative non-metal ion, which holds the ionic compound together.


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Question 17 (a)Exemplar 1 3 marks

Examiner commentaryHere candidates were expected to link the information on the diagram with their own knowledge of Rutherford’s experiment. The idea that most particles passed straight through led to a theory of the atom being mainly empty space. This candidate has described that link well. Whilst the mark scheme did not require a candidate to link points it did require them to describe the different amounts of particles that passed through and were deflected using phrases such as ‘very few’ to describe those that deflected greatly back towards the source.


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Examiner commentaryHere the candidate appears to have repeated some key words from the diagram but hasn’t clearly understood the number of particles that pass straight through or deflected. The comment ‘some were deflected a lot’ is not correct as only a very few were deflected greatly. The mark was given for the idea of a small dense nucleus (marking point 6).


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Examiner commentaryThe importance of publishing results can be for several reasons. These include checking or comparing their data, sharing their ideas so that further evidence can be collected and information can be passed to other organisations.

Question 17 (c)Exemplar 1 1 mark

Examiner commentaryMost candidates could explain that Bohr was responsible for adding electron shells to the model of the atom.


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Examiner commentaryVery few candidates gained marks on this question. It was expected that candidates would calculate the relative formula mass of compounds in the equation. They could then either calculate moles and hence the mass of ammonium nitrate or calculate the reacting ratios and scale accordingly. This candidate produced a correct answer with clear working.


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Examiner commentaryThis question was about the representations that scientists use to describe molecules. Diagram A was the simple representation of the covalent bonds between atoms within a molecule. Diagram B was a space filled molecule and diagram C was a ball and stick diagram. Candidates were expected to discuss the advantages and disadvantages of each type of diagram to display the number and types of atoms and bonds present and their overall shape. Most candidates gained at least 1 mark on this question. This answer missed the gaining the fourth mark as it only clearly describes one disadvantage that all these models do not show size of atoms. The disadvantages as well as the advantages should be clearly linked to each model in the answer.

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Exemplar Candidate Work GATEWAY SCIENCE COMBINED …