GCSE Science June 2007 Chemistry 1F Paper Ans Key

Version 1.0: 0707 abc General Certificate of Secondary Education Science B 4462 /Chemistry 4421 CHY1F Unit Chemistry 1 Mark Scheme 2007 examination -June series Mark schemes are prepared by the Principal Examiner and considered, together with the relevant questions, by a panel of subject teachers. This mark scheme includes any amendments made at the standardisation meeting attended by all examiners and is the scheme which was used by them in this examination. The standardisation meeting ensures that the mark scheme covers the candidates’ responses to questions and that every examiner understands and applies it in the same correct way. As preparation for the standardisation meeting each examiner analyses a number of candidates’ scripts: alternative answers not already covered by the mark scheme are discussed at the meeting and legislated for. If, after this meeting, examiners encounter unusual answers which have not been discussed at the meeting they are required to refer these to the Principal Examiner. It must be stressed that a mark scheme is a working document, in many cases further developed and expanded on the basis of candidates’ reactions to a particular paper. Assumptions about future mark schemes on the basis of one year’s document should be avoided; whilst the guiding principles of assessment remain constant, details will change, depending on the content of a particular examination paper. Further copies of this Mark Scheme are available to download from the AQA Website: www.aqa.org.uk Copyright © 2007 AQA and its licensors. All rights reserved. The Assessment and Qualifications Alliance (AQA) is a company limited by guarantee registered in England and Wales (company number 3644723) and a registered charity (registered charity number 1073334). Registered address: AQA, Devas Street, Manchester M15 6EX. Dr Michael Cresswell, Director General. Science B /Chemistry CHY1F -AQA GCSE Mark Scheme 2007 June series 3 MARK SCHEME Information to Examiners 1. General The mark scheme for each question shows: • the marks available for each part of the question • the total marks available for the question • the typical answer or answers which are expected • extra information to help the Examiner make his or her judgement and help to delineate what is acceptable or not worthy of credit or, in discursive answers, to give an overview of the area in which a mark or marks may be awarded. The extra information is aligned to the appropriate answer in the left-hand part of the mark scheme and should only be applied to that item in the mark scheme. At the beginning of a part of a question a reminder may be given, for example: where consequential marking needs to be considered in a calculation; or the answer may be on the diagram or at a different place on the script. In general the right hand side of the mark scheme is there to provide those extra details which confuse the main part of the mark scheme yet may be helpful in ensuring that marking is straightforward and consistent. 2. Emboldening 2.1 In a list of acceptable answers where more than one mark is available ‘any two from’ is used, with the number of marks emboldened. Each of the following lines is a potential mark. 2.2 A bold and is used to indicate that both parts of the answer are required to award the mark. 2.3 Alternative answers acceptable for a mark are indicated by the use of or. (Different terms in the mark scheme are shown by a /; eg allow smooth /free movement.) 3. Marking points 3.1 Marking of lists This applies to questions requiring a set number of responses, but for which candidates have provided extra responses. The general principle to be followed in such a situation is that ‘right + wrong = wrong’. Each error/contradiction negates each correct response. So, if the number of error/contradictions equals or exceeds the number of marks available for the question, no marks can be awarded. However, responses considered to be neutral (indicated as * in example 1) are not penalised. Science B /Chemistry CHY1F -AQA GCSE Mark Scheme 2007 June series 4 Example 1: What is the pH of an acidic solution? (1 mark) Candidate Response Marks awarded 1 4,8 0 2 green, 5 0 3 red*, 5 1 4 red*, 8 0 Example 2: Name two planets in the solar system. (2 marks) Candidate Response Marks awarded 1 Pluto, Mars, Moon 1 2 Pluto, Sun, Mars, Moon 0 3.2 Use of chemical symbols /formulae If a candidate writes a chemical symbol /formula instead of a required chemical name, full credit can be given if the symbol /formula is correct and if, in the context of the question, such action is appropriate. 3.3 Marking procedure for calculations Full marks can be given for a correct numerical answer, as shown in the column ‘answers’, without any working shown. However if the answer is incorrect, mark(s) can be gained by correct substitution /working and this is shown in the ‘extra information’ column; 3.4 Interpretation of ‘it’ Answers using the word ‘it’ should be given credit only if it is clear that the ‘it’ refers to the correct subject. 3.5 Errors carried forward Any error in the answers to a structured question should be penalised once only. Papers should be constructed in such a way that the number of times errors can be carried forward are kept to a minimum. Allowances for errors carried forward are most likely to be restricted to calculation questions and should be shown by the abbreviation e.c.f. in the marking scheme. 3.6 Phonetic spelling The phonetic spelling of correct scientific terminology should be credited unless there is a possible confusion with another technical term. 3.7 Brackets (…..) are used to indicate information which is not essential for the mark to be awarded but is included to help the examiner identify the sense of the answer required. 3.8 Unexpected Correct Answers not in the Mark Scheme The Examiner should use professional judgement to award credit where a candidate has given an unexpected correct answer which is not covered by the mark scheme. The Examiner should consult with the Team Leader to confirm the judgement. The Team Leader should pass this answer on to the Principal Examiner with a view to informing all examiners. Science B /Chemistry CHY1F -AQA GCSE Mark Scheme 2007 June series 5 CHY1F Question 1 answers extra information mark (a) low density unreactive 1 1 (b) a polymer 1 (c) any one from: • not broken down by (microorganisms) • does not decay (naturally) ignore cannot recycle /degrade /disintegrate 1 total 4 CHY1F Question 2 answers extra information mark (a)(i) additive 1 (b) any three from: • colour 1 is made up of only one colour /dye • colour 2 is made up of only one colour /dye • colour 3 is made up of two colours /dyes or more colours (than colours 1 and 2) • colours 1, 2 and 3 are all different • colour 1 is less dark than colour 2 accept colour 3 is a mixture of colours 1 and 2 for 3 marks accept E-number or additive instead of colour ignore comments about height /level 3 total 4 Science B /Chemistry CHY1F -AQA GCSE Mark Scheme 2007 June series 6 CHY1F Question 3 answers extra information mark (a) hydrogen ignore formulae 1 (b) any two from: • different sized molecules /more or less (carbon) atoms (in molecules) • fuels have different boiling points • fuels condense at different temperatures ignore different densities 2 (c) carbon dioxide global dimming global warming carbon particles non-polluting liquid crude oil non-renewable resource water toxic gas all three correct = 3 marks two correct = 2 marks one correct = 1 mark 3 total 6 Science B /Chemistry CHY1F -AQA GCSE Mark Scheme 2007 June series 7 CHY1F Question 4 answers extra information mark (a)(i) any one from: • iron ore is a limited resource /non-renewable • iron is in high demand • provide jobs • economic advantage 1 (ii) any two from: • would damage (wildlife) habitats /countryside /greenfield sites • extra traffic • visual (pollution) /eyesore • noise (pollution) /sound (pollution) • dust (pollution) • river (pollution) • carbon dioxide (from traffic) /adds to greenhouse effect /global warming • damage roads /buildings by vibrations /shockwaves 2 (b)(i) carbon monoxide /carbon accept formulae CO /C 1 (ii) atoms are all the same (size) /type accept (particles) are all the same (size) /type for one mark 1 1 Continued on next page Science B /Chemistry CHY1F -AQA GCSE Mark Scheme 2007 June series 8 Question 4 continued answers extra information mark (iii) any two from: • impurities /carbon /different (sized) atoms or elements or metals • changes the structure /disrupts the pattern or layers • prevents layers sliding over each other • it is an alloy 2 total 8 Science B /Chemistry CHY1F -AQA GCSE Mark Scheme 2007 June series 9 CHY1F Question 5 answers extra information mark (a) core mantle ignore outer or inner 1 1 (b)(i) carbon dioxide oxygen accept formula CO2 accept formulae O2 /O 1 1 (ii) 4% 1 (iii) carbon dioxide has decreased /from 95% to 0% oxygen has increased /from 0% to 21% any one from: (carbon dioxide decrease) • carbon dioxide used during photosynthesis /by plants • carbon dioxide dissolves in oceans • carbon dioxide is locked up in rocks /carbonates /fossil fuels (oxygen increase) • oxygen released during photosynthesis /by plants 1 1 1 total 8 Science B /Chemistry CHY1F -AQA GCSE Mark Scheme 2007 June series 10 CHY1F Question 6 answers extra information mark (a) any two from: • nitrogen • carbon dioxide • water (vapour) /steam accept formulae N /N2 accept formula CO2 ignore CO accept formula H2O 2 (b) any three from: limestone • abundant /local • natural material or no ‘processing’ needed • relatively easy to cut • appearance better concrete • raw materials are abundant • can be reinforced (by steel rods) /strong(er) /supported (by steel rods) • concrete mixture can be poured /moulded /constructed on site • less reactive with acid rain /weathering /erosion no mark for ‘limestone’ or ‘concrete’ on first line – mark advantages only ignore ideas of speed of production or easier to use accept ‘can build higher’ ignore density /extraction /quarrying /pollution /cost 3 total 5 Science B /Chemistry CHY1F -AQA GCSE Mark Scheme 2007 June series 11 CHY1F Question 7 answers extra information mark (a)(i) Cu2S + 2O2 → 2CuO + SO2 accept fractions and multiples 1 (ii) any two from: • sulfur dioxide • causes acid rain • consequence of acid rain eg kills fish /plants accept sulphur dioxide /sulphur oxide /SO2 ignore other comments eg global warming /ozone /global dimming /greenhouse effect 2 (b) any two from: • heat (copper oxide with carbon) • oxygen is removed by carbon or carbon monoxide /carbon dioxide is produced or carbon displaces copper • because carbon is more reactive than copper accept copper (oxide) loses oxygen or carbon gains oxygen accept carbon oxide accept a correct word or balanced symbol equation allow a correct comparison of reactivity 2 (c)(i) electrolysis accept electroplating 1 (ii) (electrical) wiring /appliances /coins /pipes /cladding for buildings /jewellery /making alloys or named alloys 1 Continued on next page Science B /Chemistry CHY1F -AQA GCSE Mark Scheme 2007 June series 12 Question 7 continued answers extra information mark (d) any three explanations from: for recycling • less acid rain (pollution) • copper reserves last longer /conserved or do not run out • energy for extraction (saved) or less energy required • less mining /quarrying • less waste (copper) /electrical appliances dumped or less landfill against recycling • collection problems • transport problems • difficult to separate copper from appliances • energy used to melt the collected copper ignore electrolysis /pollution ignore ideas about less machinery /plant ignore idea of cost 3 total 10