GCSE CHEMISTRY 8462/2H Paper 2 Higher Tier Mark scheme June 2020 Version: 1.0 Final Mark Scheme

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GCSE CHEMISTRY 8462/2H Paper 2 Higher Tier Mark scheme June 2020 Version: 1.0 Final Mark Scheme GCSE CHEMISTRY 8462/2H Paper 2 Higher Tier Mark scheme June 2020 Version: 1.0 Final Mark Scheme ... *206G8462/2H/MS*MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 2 Mark schemes are prepared by the Lead Assessment Writer and considered, together with the relevant questions, by a panel of subject teachers. This mark scheme includes any amendments made at the standardisation events which all associates participate in and is the scheme which was used by them in this examination. The standardisation process ensures that the mark scheme covers the students’ responses to questions and that every associate understands and applies it in the same correct way. As preparation for standardisation each associate analyses a number of students’ scripts. Alternative answers not already covered by the mark scheme are discussed and legislated for. If, after the standardisation process, associates encounter unusual answers which have not been raised they are required to refer these to the Lead Examiner. It must be stressed that a mark scheme is a working document, in many cases further developed and expanded on the basis of students’ 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 from aqa.org.uk Copyright information AQA retains the copyright on all its publications. However, registered schools/colleges for AQA are permitted to copy material from this booklet for their own internal use, with the following important exception: AQA cannot give permission to schools/colleges to photocopy any material that is acknowledged to a third party even for internal use within the centre. Copyright © 2020 AQA and its licensors. All rights reserved.MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 3 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 • the Assessment Objectives, level of demand and specification content that each question is intended to cover. 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 and underlining 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 bullet points 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. 2.4 Any wording that is underlined is essential for the marking point to be awarded.MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 4 3. Marking points 3.1 Marking of lists This applies to questions requiring a set number of responses, but for which students 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. Example 1: What is the pH of an acidic solution? [1 mark] Student Response Marks awarded 1 green, 5 0 2 red*, 5 1 3 red*, 8 0 Example 2: Name two planets in the solar system. [2 marks] Student Response Marks awarded 1 Neptune, Mars, Moon 1 2 Neptune, Sun, Mars, Moon 0 3.2 Use of chemical symbols / formulae If a student 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 Marks should be awarded for each stage of the calculation completed correctly, as students are instructed to show their working. Full marks can, however, be given for a correct numerical answer, without any working shown. 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.MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 5 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 is 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 ecf 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 Allow In the mark scheme additional information, ‘allow’ is used to indicate creditworthy alternative answers. 3.9 Ignore Ignore is used when the information given is irrelevant to the question or not enough to gain the marking point. Any further correct amplification could gain the marking point. 3.10 Do not accept Do not accept means that this is a wrong answer which, even if the correct answer is given as well, will still mean that the mark is not awarded.MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 6 4. Level of response marking instructions Extended response questions are marked on level of response mark schemes. • Level of response mark schemes are broken down into levels, each of which has a descriptor. • The descriptor for the level shows the average performance for the level. • There are two marks in each level. Before you apply the mark scheme to a student’s answer, read through the answer and annotate it (as instructed) to show the qualities that are being looked for. You can then apply the mark scheme. Step 1: Determine a level Start at the lowest level of the mark scheme and use it as a ladder to see whether the answer meets the descriptor for that level. The descriptor for the level indicates the different qualities that might be seen in the student’s answer for that level. If it meets the lowest level then go to the next one and decide if it meets this level, and so on, until you have a match between the level descriptor and the answer. When assigning a level you should look at the overall quality of the answer. Do not look to penalise small and specific parts of the answer where the student has not performed quite as well as the rest. If the answer covers different aspects of different levels of the mark scheme you should use a best fit approach for defining the level. Use the variability of the response to help decide the mark within the level, ie if the response is predominantly level 2 with a small amount of level 3 material it would be placed in level 2 but be awarded a mark near the top of the level because of the level 3 content. Step 2: Determine a mark Once you have assigned a level you need to decide on the mark. The descriptors on how to allocate marks can help with this. The exemplar materials used during standardisation will help. There will be an answer in the standardising materials which will correspond with each level of the mark scheme. This answer will have been awarded a mark by the Lead Examiner. You can compare the student’s answer with the example to determine if it is the same standard, better or worse than the example. You can then use this to allocate a mark for the answer based on the Lead Examiner’s mark on the example. You may well need to read back through the answer as you apply the mark scheme to clarify points and assure yourself that the level and the mark are appropriate. Indicative content in the mark scheme is provided as a guide for examiners. It is not intended to be exhaustive and you must credit other valid points. Students do not have to cover all of the points mentioned in the indicative content to reach the highest level of the mark scheme. You should ignore any irrelevant points made. However, full marks can be awarded only if there are no incorrect statements that contradict a correct response. An answer which contains nothing of relevance to the question must be awarded no marks.MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 7 Question 1 Question Answers Extra information Mark AO / Spec. Ref. 01.1 green allow blue-green 1 AO1 4.8.3.1 RPA 7 01.2 did not clean the metal wire (between tests) or copper sulfate (solution) is still present (so) colours are mixed / blended / masked 1 1 AO3 4.8.3.1 RPA 7 01.3 (copper sulfate solution) blue precipitate (calcium iodide solution) white precipitate allow blue solid allow white solid 1 1 AO1 4.8.3.2 RPA 7 01.4 barium chloride (solution) allow barium nitrate (solution) 1 AO1 4.8.3.5 RPA 7 01.5 silver nitrate (solution) yellow precipitate allow yellow solid allow pale yellow precipitate / solid 1 1 AO1 4.8.3.4 RPA 7 Total 8MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 8 Question 2 Question Answers Mark AO/ Spec. Ref 02.1 Level 2: Relevant points (reasons/causes) are identified, given in detail and logically linked to form a clear account. 3–4 AO1 4.10.1.2 Level 1: Points are identified and stated simply, but their relevance is not clear and there is no attempt at logical linking. 1–2 No relevant content 0 Indicative content • choose an appropriate source of fresh water • such as rivers, streams, lakes, boreholes • pass through filter beds • (which) removes undissolved solids • sterilise • using chlorine / ozone / UV light • (which) destroys harmful microbes Question Answers Extra information Mark AO / Spec. Ref. 02.2 any one from: • distillation • reverse osmosis allow use of membranes allow desalination 1 AO3 4.10.1.2 02.3 additional line from a box on the left negates the mark for that box 1 1 AO1 4.10.1.3MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 9 Question 2 (continued) Question Answers Extra information Mark AO / Spec. Ref. 02.4 260 x 100 1413 = 18.40056617 (%) = 18.4 (%) allow an answer correctly calculated to 3 significant figures from an incorrect percentage calculation which uses values in the question 1 1 1 AO2 4.10.1.3 02.5 any one from: • the population increased • more waste water produced • less untreated sewage discharged 1 AO3 4.10.1.3 02.6 any two from: • increased demand for food (due to increasing population) • conserves energy / resources • landfill space is running out • increased demand for organic fertiliser ignore references to cost allow more farming allow more sustainable allow more awareness of the negative environmental impacts of landfill ignore less sent to landfill allow lifestyle choice for organic food 2 AO3 4.10.1.3 Total 13MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 10 Question 3 Question Answers Extra information Mark AO / Spec. Ref. 03.1 additional line from a box on the left negates the mark for that box 1 1 AO2 4.7.1.1 4.7.2.1 03.2 (remains) orange (becomes) colourless must be in this order allow no (colour) change ignore initial colour ignore clear 1 1 AO2 4.7.1.4MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 11 Question 3 (continued) Question Answers Mark AO/ Spec. Ref 03.3 Level 2: Scientifically relevant features are identified; the way(s) in which they are similar/different is made clear and (where appropriate) the magnitude of the similarity/difference is noted. 4–6 AO1 AO2 Level 1: Relevant features are identified and differences noted. 1–3 No relevant content 0 4.7.1.1 4.7.1.3 4.7.1.4 4.7.2.1 4.7.2.2 4.9.3.1 Indicative content Structure and bonding • both are hydrocarbons • both contain two carbon atoms (per molecule) • ethane contains six hydrogen atoms (per molecule) • (but) ethene contains four hydrogen atoms (per molecule) • both have covalent bonds • ethane contains a single C—C bond • (but) ethene contains a double bond • both contain C—H bonds • both small molecules Reactions • both react with oxygen in complete combustion reactions • to produce water and carbon dioxide • both react with oxygen in incomplete combustion reactions • to produce water, carbon monoxide and carbon • incomplete combustion is more likely with ethene • ethene decolourises bromine water • (but) ethane does not decolourise bromine water • ethene is more reactive (than ethane) • ethene can react with hydrogen (to produce ethane) • ethene can react with water (to produce ethanol) • ethene can react with halogens (to produce halogenoalkanes) • ethene can undergo addition reactions • ethene can polymerise (to produce poly(ethene)) ignore physical properties ignore references to flammability Total 10MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 12 Question 4 Question Answers Extra information Mark AO / Spec. Ref. 04.1 0.60 = 5.7 distance moved by solvent (distance moved by solvent =) 5.7 0.60 = 9.5 (cm) 1 1 1 AO2 4.8.1.3 RPA6 04.2 some of the compounds are colourless (in solution) or dyes / compounds have the same Rf values allow there are only two compounds that are coloured (in solution) 1 AO3 4.8.1.3 RPA6 04.3 allow the solvent front to travel further use a different solvent 1 1 AO3 4.8.1.3 RPA6 04.4 so that the (shade of) green is the same allow because the green ink is a formulation 1 AO3 4.8.1.2 04.5 the dye is less soluble in the new solvent and more attracted to the new paper 1 AO3 4.8.1.3 Total 8MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 13 Question 5 Question Answers Extra information Mark AO / Spec. Ref. 05.1 any two from: energy used in: • extraction of raw materials • processing raw materials • manufacturing • transportation • cleaning non-disposable plates • disposal • recycling allow energy used to make food plate materials 2 AO3 4.10.2.1MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 14 Question 5 (continued) Question Answers Mark AO/ Spec. Ref 05.2 Level 2: A judgement, strongly linked and logically supported by a sufficient range of correct reasons, is given. 3‒4 AO3 4.10.1.1 4.10.2.1 4.10.2.2 Level 1: Some logically linked reasons are given. There may also be a simple judgement. 1‒2 No relevant content 0 Indicative content Raw materials • Trees are renewable • Crude oil and clay are finite Manufacturing and packaging • Paper plates use the least packaging so conserve raw materials • Paper plates need less transportation overall as more plates in a 10 dm3 cardboard box Use and operation • Paper plates are single use so must be replaced most often • Ceramic plates last longer than polymer plates so must be replaced less often Disposal • Polymer / ceramic plates take up landfill which is running out • Paper / polymer plates can be used to make new products • Recycling conserves raw materials Reasoned judgement Question Answers Extra information Mark AO / Spec. Ref. 05.3 (wet) clay is shaped (and) heated in a furnace allow (and) heated in a kiln / oven allow (and) fired 1 1 AO1 4.10.3.3 Total 8MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 15 Question 6 Question Answers Extra information Mark AO / Spec. Ref. 06.1 incomplete combustion (because of) insufficient oxygen max 1 mark if soot wrongly identified 1 1 AO1 4.9.3.1 06.2 sulfur reacts with oxygen to form sulfur dioxide (so) less sulfur dioxide emitted (so) less acid rain (so less) limestone reacts with acid rain allow SO2 for sulfur dioxide allow sulfur burns to form sulfur dioxide 1 1 1 1 AO1 AO1 AO2 AO2 4.9.3.1 4.9.3.2 06.3 (car engines work at) high temperatures (so in the engine) nitrogen (from air) reacts with oxygen (from air) 1 1 AO1 4.9.3.1 Total 8MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 16 Question 7 Question Answers Extra information Mark AO / Spec. Ref. 07.1 HCOOH propanoic acid allow HCO2H 1 1 AO1 4.7.2.4 07.2 incomplete / partial ionisation (because) reaction is reversible allow incomplete / partial dissociation allow (because) reaction is in equilibrium 1 1 AO3 4.7.2.4 07.3 mass (of flask and contents) decreases (because) carbon dioxide is produced (and) carbon dioxide escapes (from the flask) allow 1 mark for the gas produced escapes (from the flask) 1 1 1 AO1 AO2 AO2 4.3.1.3 4.7.2.4 07.4 (0.01 mol/dm3) methanoic acid has a lower pH (so 0.01 mol/dm3) methanoic acid has a higher concentration of hydrogen ions (therefore) more collisions per unit time allow converse argument for ethanoic acid allow (0.01 mol/dm3) methanoic acid is a stronger acid 1 1 1 AO2 AO2 AO3 4.6.1.2 4.6.1.3 4.7.2.4 07.5 ethyl ethanoate 1 AO1 4.7.2.4MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 17 Question 7 (continued) Question Answers Extra information Mark AO / Spec. Ref. 07.6 1 AO2 4.7.2.4 4.7.3.2 Total 12MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 18 Question 8 Question Answers Extra information Mark AO / Spec. Ref. 08.1 all seven points plotted correctly line of best fit allow a tolerance of ±½ small square allow 1 mark for five or six points plotted correctly 2 1 AO2 4.6.1.1 08.2 0.0038 and 0.0014 0.0038 - 0.0014 105 - 20 = 0.000028 or = 2.8 x 10-5 mol/s allow correct use of incorrectly determined mole value(s) allow moles per second 1 1 1 1 AO2 4.6.1.1 08.3 (for large lumps) a smaller number of moles of gas is collected in the same time or (for large lumps) more time is needed to collect the same number of moles of gas or the line (of best fit for large lumps) is less steep allow converse statement for small lumps allow the line (of best fit for large lumps) takes more time to become horizontal 1 AO2 4.6.1.1MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 19 Question 8 (continued) Question Answers Extra information Mark AO / Spec. Ref. 08.4 (surface area = 6 x 0.5 x 0.5) = 1.5 (cm2) (volume = 0.5 x 0.5 x 0.5) = 0.125 (cm3) (surface area : volume =) 12 : 1 allow correctly calculated ratio using incorrectly calculated values for surface area and/or volume 1 1 1 AO2 4.6.1.3 08.5 decreases by a factor of 10 allow 10 times smaller allow one tenth allow 1/10 allow 1 : 10 (large cube to small cube) 1 AO2 4.2.4.1 4.6.1.3 Total 12MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 20 Question 9 Question Answers Extra information Mark AO / Spec. Ref. 09.1 test: (use a) glowing splint result: relights do not accept burning splint dependent on correct test in MP1 ignore with a pop 1 1 AO1 4.8.2.2 4.9.1.3 09.2 starch cellulose allow glycogen 1 1 AO1 4.7.3.4 09.3 2 1 AO1 4.7.3.3 09.4 water allow H2O 1 AO1 4.7.3.3 09.5 ammonia nitrogen if no other mark awarded, allow 1 mark for NO / NO2 / N2O / NOx or equivalent named compounds 1 1 AO3 4.7.3.3 4.9.1.2MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 21 Question 9 (continued) Question Answers Extra information Mark AO / Spec. Ref. 09.6 two polymer chains four (different) monomers / nucleotides (double) helix allow two polymer strands allow four (different) bases allow cytosine, guanine, adenine and thymine allow C G A T allow spiral if no other mark awarded, allow 1 mark for DNA 1 1 1 AO1 4.7.3.4 Total 11MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 22 Question 10 Question Answers Extra information Mark AO / Spec. Ref. 10.1 water allow H2O 1 AO1 4.2.2.2 10.2 becomes (more) red (because the position of) equilibrium moves to the right (so that) the (increase in the) concentration of thiocyanate (ions) is reduced allow (because) the concentration of FeSCN2+ (ions) increases allow (because) the forward reaction is favoured allow (so that) the increase in the concentration of thiocyanate (ions) is counteracted 1 1 1 AO2 4.6.2.4 4.6.2.5 10.3 (the position of) equilibrium moves to the left (so that) the (increase in the) temperature is reduced (therefore) the forward reaction is exothermic allow the concentration of Fe3+ (ions) increases allow the reverse reaction is favoured allow (so that) the increase in the temperature is counteracted allow (therefore) the forward reaction releases energy (to the surroundings) 1 1 1 AO2 4.6.2.4 4.6.2.6MARK SCHEME – GCSE CHEMISTRY – 8462/2H – JUNE 2020 23 Question 10 (continued) Question Answers Extra information Mark AO / Spec. Ref. 10.4 no change in equilibrium position (because) no gases are present allow (because) only aqueous solutions are present 1 1 AO2 4.6.2.7 10.5 Co2+ 1 AO2 4.1.3.2 4.6.2.5 [Show More]

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