GCSE Chemistry A

GCSEChemistry AUnit J248H/03: Higher Tier – Paper 3General Certificate of Secondary EducationMark Scheme for June 2018Oxford Cambridge and RSA Examinations

OCR (Oxford Cambridge and RSA) is a leading UK awarding body, providing a wide range ofqualifications to meet the needs of candidates of all ages and abilities. OCR qualifications includeAS/A Levels, Diplomas, GCSEs, Cambridge Nationals, Cambridge Technicals, Functional Skills,Key Skills, Entry Level qualifications, NVQs and vocational qualifications in areas such as IT,business, languages, teaching/training, administration and secretarial skills.It is also responsible for developing new specifications to meet national requirements and theneeds of students and teachers. OCR is a not-for-profit organisation; any surplus made is investedback into the establishment to help towards the development of qualifications and support, whichkeep pace with the changing needs of today’s society.This mark scheme is published as an aid to teachers and students, to indicate the requirements ofthe examination. It shows the basis on which marks were awarded by examiners. It does notindicate the details of the discussions which took place at an examiners’ meeting before markingcommenced.All examiners are instructed that alternative correct answers and unexpected approaches incandidates’ scripts must be given marks that fairly reflect the relevant knowledge and skillsdemonstrated.Mark schemes should be read in conjunction with the published question papers and the report onthe examination. OCR 2018

J248/03Mark SchemeAnnotations available in RM AssessorAnnotationMeaningCorrect responseIncorrect responseOmission markBenefit of doubt givenContradictionRounding errorError in number of significant figuresError carried forwardLevel 1Level 2Level 3Benefit of doubt not givenNoted but no credit givenIgnore3June 2018

J248/03Mark SchemeJune 2018Abbreviations, annotations and conventions used in the detailed Mark Scheme (to include abbreviations and subject-specific conventions).AnnotationMeaning/alternative and acceptable answers for the same marking point Separates marking pointsDO NOT ALLOWAnswers which are not worthy of creditIGNOREStatements which are irrelevantALLOWAnswers that can be accepted()Words which are not essential to gain creditUnderlined words must be present in answer to score a markECFError carried forwardAWAlternative wordingORAOr reverse argument4

J248/03Post Standardisation Mark SchemeJune 2018Subject-specific Marking InstructionsINTRODUCTIONYour first task as an Examiner is to become thoroughly familiar with the material on which the examination depends. This material includes: the specification, especially the assessment objectives the question paper the mark scheme.You should ensure that you have copies of these materials.You should ensure also that you are familiar with the administrative procedures related to the marking process. These are set out in the OCRbooklet Instructions for Examiners. If you are examining for the first time, please read carefully Appendix 5 Introduction to Script Marking:Notes for New Examiners.Please ask for help or guidance whenever you need it. Your first point of contact is your Team Leader.5

J248/03Post Standardisation Mark SchemeJune 2018The breakdown of Assessment Objectives for GCSE (9-1) in Chemistry:Assessment ObjectiveAO1Demonstrate knowledge and understanding of scientific ideas and scientific techniques and procedures.AO1.1Demonstrate knowledge and understanding of scientific ideas.AO1.2Demonstrate knowledge and understanding of scientific techniques and procedures.AO2Apply knowledge and understanding of scientific ideas and scientific enquiry, techniques and procedures.AO2.1Apply knowledge and understanding of scientific ideas.AO2.2Apply knowledge and understanding of scientific enquiry, techniques and procedures.AO3AO3.1Analyse information and ideas to interpret and evaluate, make judgements and draw conclusions and develop and improveexperimental procedures.Analyse information and ideas to interpret and evaluate.AO3.1aAnalyse information and ideas to interpret.AO3.1bAnalyse information and ideas to evaluate.AO3.2Analyse information and ideas to make judgements and draw conclusions.AO3.2aAnalyse information and ideas to make judgements.AO3.2bAnalyse information and ideas to draw conclusions.AO3.3Analyse information and ideas to develop and improve experimental procedures.AO3.3aAnalyse information and ideas to develop experimental procedures.AO3.3bAnalyse information and ideas to improve experimental procedures.6

J248/03Mark schemeJune 2018SECTION AFor answers to Section A if an answer box is blank ALLOW correct indication of answer e.g. circled or underlined.1C 1AOelement1.22C 11.13A 11.14C 11.15D 12.16C 11.17A 11.18A 11.29B 11.110C 11.111C 11.212C 11.113D 11.114C 11.115C 11.1QuestionAnswerMarks7Guidance

J248/03Mark schemeJune 2018SECTION BQuestion16 (a)(i)AnswerMarksParticles close together / particles compact / particlesalready touching / particles tightly packed / AW 1AOelement1.1GuidanceALLOW idea of particles with no spaces betweenthemALLOW any type of particlesMark can be awarded from a diagramIGNORE particles are in fixed positionsIGNORE particles are in a regular arrangement /particles are in a latticeIGNORE intermolecular forces(a)(ii)Any three from:33 x 1.1ALLOW any type of particlesParticles in a solid are in fixed positions Particles in a solid vibrate ALLOW particles in a solid cannot move (past eachother)IGNORE solid cannot flow, but ALLOW particles in asolid cannot flowIGNORE particles move around on the spotParticles in a liquid can move (past each other) IGNORE liquid can flow, but ALLOW particles in aliquid can flowas forces between particles in a liquid are less than ina solid ALLOW liquid particles have enough energy toovercome attractions (between particles)DO NOT ALLOW no forces between particlesIGNORE intermolecular forces8

J248/03Mark schemeQuestion(a)AnswerMarks(iii) Any two from:2June 2018AOelement2 x 1.1GuidanceALLOW any type of particlesParticles are moving quickly (in all directions) ALLOW particles can move freely or randomlyParticles are far apart ALLOW M2 from a diagram showing no particlestouchingParticles spread out Weak forces between the particles IGNORE intermolecular forcesIGNORE no forces between particles(b)Mg 2H2O Mg(OH)2 H22Correct formulae Balancing Balancing mark is conditional on correct formulae1.12.2ALLOW or instead of DO NOT ALLOW and or & instead of ALLOW any correct multiples including fractionse.g. 2Mg 4H2O 2Mg(OH)2 2H2ALLOW one mark for correct equation with minorerrors in case, subscript or superscript e.g.MG 2H2O 2Mg(OH)2 H2IGNORE state symbols(c)148.3 192.2ALLOW 148

J248/03Mark schemeQuestion17 (a)AnswerJune 2018MarksANY FOUR FROM:Titration 4AOGuidanceelement4 x 3.3a ALLOW other methods involving addingacid to sodium hydroxide solution usingthe principles outlined on the LHSeg ALLOW mix or react acid with alkaliPut acid in burette Pipette (a known volume of) sodium hydroxide into flask ALLOW alkali in buretteALLOW acid in flaskUse a (named) indicator / use of a pH meter Add acid to sodium hydroxide until colour of indicator changes Repeat (to get an accurate value) Repeat again with no indicator Evaporate (off the water) / crystallise DO NOT ALLOW marks in incorrectcontext(b)NaOH HCl NaCl H2O 12.2ALLOW or instead of DO NOT ALLOW and or & instead of ALLOW any correct multiples includingfractions(c)(d)Acid usedOther starting materialSalt madesulfuric acidcopper oxidecopper sulfate nitric acid zinc carbonatezinc nitratehydrochloric acidmagnesium oxide/magnesium hydroxide /magnesium carbonate /magnesium magnesium chlorideNeutralisation 1033 x 2.212.2IGNORE any state symbolsALLOW correct formulae

J248/03Mark schemeQuestion18 (a)AnswerMarksIdea that ethanol and /or petrol are flammable 2June 2018AOGuidanceelement2 x 3.3b Marking points are independentSo need to use a water bath or heating mantle (b)ALLOW use an electric heaterState of propane is gas 22 x 2.122 x 2.1State of hexane is liquid (c)C3H8 5O2 3CO2 4H2OBalancing mark is conditional on correct formulaeALLOW or instead of Correct formulae Balancing DO NOT ALLOW and or & instead of ALLOW any correct multiples including fractionse.g. 2C3H8 10O2 6CO2 8H2OALLOW one mark for correct equation with minorerrors in case, subscript or superscript e.g.C3H8 5O2 3CO2 4H2oIGNORE state symbols11

J248/03Mark schemeQuestion19 (a)(b)June 2018AnswerMarksNumber of protons (in the nucleus of an atom) 1Isotopes have the same number of protons but different numbers of neutrons/ same atomic number but different mass numbers /atoms of the same element with the different number of neutrons ordifferent mass numbers 1AOGuidanceelementALLOW number of electrons in1.1an atomALLOW answer in terms of Cl,ie it has 17 protons1.1IGNORE same number ofelectronsALLOW answer in terms of Cl,ie one Cl atom has 18 neutronsand one Cl atom has 20 neutronsORone Cl atom has a mass numberof 35 and one Cl atom has amass number of 37IGNORE different relative atomicmasses(c)4AtomNumber NumberNumberAtomicMassElectronicorofofofnumber numberstructureionprotons neutrons electronsS16321616162.8.6 BF51155 2.39199610 102.8Li 373422 121 x 1.13 x 2.1Mark for each correct line oftable

J248/03Mark schemeQuestion(d)AnswerJune 2018Marks(i)3AOGuidanceelementALLOW electrons as all dots, all3 x 2.1crosses, or a mix of dots andcrossesALLOW diagrams without innerelectron shell, but inner shellmust be correct if shownORsodium ion, Na DO NOT ALLOW S for Naor O2 for O (for drawing of ionsmarks)oxide ion, O2-Sodium ion drawn correctly Oxide ion drawn correctly Correct charges on both ions ALLOW answers showing thetransfer of electrons providing thesame electrons are not showntwiceDO NOT ALLOW diagramshowing sharing of electrons 0 marks(ii) Na2O 12.1DO NOT ALLOW Na2O / Na2OALLOW correct formula for Na2Oin an equation (even ifunbalanced)13

J248/03Mark schemeQuestion20 (a)(b)AnswerMarksFilter to remove the sand (as) sand is insoluble in water / sodium chloride is soluble 4June 2018AOGuidanceelementALLOW MAX 3 marks if method is in wrong order,3.3a3.1beg distillation before filtrationDistil the filtered mixture 3.3aALLOW fractional distillationALLOW boil and condense for ‘distil’DO NOT ALLOW evaporation / crystallisation(Solid) sodium chloride stays in flask and pure watercondenses 3.1bALLOW idea that (solid) sodium chloride stays inflask once pure water has evaporated3No (no mark)Any two from:Idea that sample 4 has range higher than 110oC MAX 2 if answer refers to boiling points2 x 3.2aPure sample of B cannot have melting point above 110oC Idea that pure samples do not melt over a range (oftemperatures) / ORA /Pure samples have a specific melting point / ORA Impurities lower the melting point ANDSample 1 is likely to be most pure 1 x 3.2b14IGNORE just ‘the melting point of sample 4 is110 - 112 C’

J248/03Mark schemeQuestionAnswerJune 2018Marks21 (a)AOelementGuidance3CuSO4 5H2OCuSO4.5H2OReactants and products labelled in words or formulae, withproducts shown below reactants 2.2Energy change labelled 1.2DO NOT ALLOW double headed arrow or linewithout arrowActivation energy labelled 1.2DO NOT ALLOW double headed arrow or linewithout arrowALLOW 1 mark MAX for correctly labelledactivation energy on an endothermic reactionprofile15