GCSE Additional Science (Route 2)

Transcription

1 GCSE Additional Science (Route 2) AS2HP Mark scheme 4409 June 205 Version/Stage:.0 Final

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 crect way. As preparation f standardisation each associate analyses a number of students scripts: alternative answers not already covered by the mark scheme are discussed and legislated f. If, after the standardisation process, associates encounter unusual answers which have not been raised they are required to refer these to the Lead Assessment Writer. It must be stressed that a mark scheme is a wking 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.g.uk Copyright 205 AQA and its licenss. All rights reserved. AQA retains the copyright on all its publications. However, registered schools/colleges f AQA are permitted to copy material from this booklet f their own internal use, with the following imptant exception: AQA cannot give permission to schools/colleges to photocopy any material that is acknowledged to a third party even f internal use within the centre.

3 MARK SCHEME GCSE ADDITIONAL SCIENCE (ROUTE 2) AS2HP JUNE 205. General Infmation to Examiners The mark scheme f each question shows: the marks available f each part of the question the total marks available f the question the typical answer answers which are expected extra infmation to help the Examiner make his her judgement and help to delineate what is acceptable not wthy of credit, in discursive answers, to give an overview of the area in which a mark marks may be awarded the Assessment Objectives and specification content that each question is intended to cover. The extra infmation 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, f example: where consequential marking needs to be considered in a calculation; the answer may be on the diagram 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 straightfward and consistent. 2. Emboldening 2. In a list of acceptable answers where me 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 f a mark are indicated by the use of. Different terms in the mark scheme are shown by a / ; eg allow smooth / free movement. 2.4 Any wding that is underlined is essential f the marking point to be awarded. 3. Marking points 3. Marking of lists This applies to questions requiring a set number of responses, but f which students have provided extra responses. The general principle to be followed in such a situation is that right + wrong = wrong. Each err / contradiction negates each crect response. So, if the number of errs / contradictions equals exceeds the number of marks available f the question, no marks can be awarded. However, responses considered to be neutral (indicated as * in example ) are not penalised. 3 of 9

4 MARK SCHEME GCSE ADDITIONAL SCIENCE (ROUTE 2) AS2HP JUNE 205 Example : What is the ph of an acidic solution? ( mark) Student Response Marks awarded green, red*, 5 3 red*, 8 0 Example 2: Name two planets in the solar system. (2 marks) Student Response Marks awarded Neptune, Mars, Moon 2 Neptune, Sun, Mars, Moon Use of chemical symbols / fmulae If a student writes a chemical symbol / fmula instead of a required chemical name, full credit can be given if the symbol / fmula is crect and if, in the context of the question, such action is appropriate. 3.3 Marking procedure f calculations Full marks can be given f a crect numerical answer, without any wking shown. However, if the answer is increct, mark(s) can be gained by crect substitution / wking and this is shown in the extra infmation column by each stage of a longer calculation. 3.4 Interpretation of it Answers using the wd it should be given credit only if it is clear that the it refers to the crect subject. 3.5 Errs carried fward Any err 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 errs can be carried fward is kept to a minimum. Allowances f errs carried fward 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 crect scientific terminology should be credited unless there is a possible confusion with another technical term. 3.7 Brackets (..) are used to indicate infmation which is not essential f the mark to be awarded but is included to help the examiner identify the sense of the answer required. 4 of 9

5 MARK SCHEME GCSE ADDITIONAL SCIENCE (ROUTE 2) AS2HP JUNE Accept / allow Accept is used to indicate an equivalent answer to that given on the left-hand side of the mark scheme. Allow is used to denote lower-level responses that just gain credit. 3.9 Igne / Insufficient / Do not allow Igne of insufficient is used when the infmation given is irrelevant to the question not enough to gain the marking point. Any further crect amplification could gain the marking point. Do not allow means that this is a wrong answer which, even if the crect answer is given, will still mean that the mark is not awarded. 4. Quality of Communication and levels marking In Question 2(c) students are required to produce extended written material in English, and will be assessed on the quality of their communication as well as the standard of the scientific response. Students will be required to: use good English ganise infmation clearly use specialist vocabulary where appropriate. The following general criteria should be used to assign marks to a level: Level : basic Knowledge of basic infmation Simple understanding The answer is poly ganised, with almost no specialist terms and their use demonstrating a general lack of understanding of their meaning, little no detail The spelling, punctuation and grammar are very weak. Level 2: clear Knowledge of accurate infmation Clear understanding The answer has some structure and ganisation, use of specialist terms has been attempted but not always accurately, some detail is given There is reasonable accuracy in spelling, punctuation and grammar, although there may still be some errs. Level 3: detailed Knowledge of accurate infmation appropriately contextualised Detailed understanding, suppted by relevant evidence and examples Answer is coherent and in an ganised, logical sequence, containing a wide range of appropriate relevant specialist terms used accurately. The answer shows almost faultless spelling, punctuation and grammar. 5 of 9

6 MARK SCHEME GCSE ADDITIONAL SCIENCE (ROUTE 2) AS2HP JUNE 205 Question Answers Extra infmation Mark (a) amino acid(s) AO2 B2.5.2 e (b)(i) so they reach same temperature / 5 o C allow so they do not react at the wrong temperature so they react at the right temperature AO3 B2.5.2 (b)(ii) 3 AO3 B2.5.2 (c)(i) it doubles f each 0 o C rise allow exponential increase allow (volume of egg white digested) increases f mark 2 AO2 B2.5.2 (c)(ii) do / repeat at other temperature(s) (in the range 0 50 o C) igne repeat without qualification AO2 B2.5.2 between 30 and 40 ( o C) between 40 and 50 ( o C) between 30 and 50 ( o C) around 40 ( o C) allow eg ref to 37 ( o C) igne ref to body temperature (c)(iii) protease / enzyme is not killed protease / enzyme is not living mark together AO2 B2.5.2 a/j reference to protease / enzyme being denatured / destroyed allow description of denaturation, eg active site / shape changed Total 9 6 of 9

7 MARK SCHEME GCSE ADDITIONAL SCIENCE (ROUTE 2) AS2HP JUNE 205 Question Answers Extra infmation Mark 2(a) base. AO C2.6.2a 2(b) (s) (aq) (l) in this der only award 2 marks f all three crect award mark if one two are crect 2 AO C2.6.a 7 of 9

8 MARK SCHEME GCSE ADDITIONAL SCIENCE (ROUTE 2) AS2HP JUNE 205 QWC Mark Scheme Question Answers Extra infmation Mark 2(c) 6 AO, AO2 C2.6.b/c Marks awarded f this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response. Examiners should also refer to the infmation on page 5 and apply a best-fit approach to the marking. 0 marks Level ( 2 marks) Level 2 (3 4 marks) Level 3 (5 6 marks) No relevant comment. A simple statement is made about the reaction separation crystallisation Statements are made in a sensible sequence about the reaction and separation the reaction and crystallisation separation and crystallisation but some steps may be missing. Statements are made in a sensible sequence about the reaction, separation and crystallisation in an ganised method. examples of points made in the response Reaction place sulfuric acid in beaker gently warm sulfuric acid add magnesium oxide (using a spatula) stir mixture of magnesium oxide and sulfuric acid add magnesium oxide until no me will react extra infmation igne references to colours of reactants and products allow diagrams showing crect use of equipment Separation filter mixture (to remove excess solid/magnesium oxide) Crystallisation heat filtrate in evapating dish until half volume remains pour into a crystallising dish leave to crystallise Total 9 8 of 9

9 MARK SCHEME GCSE ADDITIONAL SCIENCE (ROUTE 2) AS2HP JUNE 205 Question Answers Extra infmation Mark 3(a)(i) live (wire) AO P2.4. f 3(a)(ii) double insulated allow it is not made of metal AO2 P2.4. f / j wood is an (electrical) insulat allow wood is not an (electrical) conduct it is wooden is insufficient igne it has only two wires in cable 3(a)(iii) because plastic is an (electrical) insulat allow does not conduct (electricity) AO P2.4. f igne other features of plastic 3(a)(iv) if the current (in the fuse) exceeds 3 A AO P2.4. h the fuse will melt allow the fuse will blow / break 3(b) it has a frequency of 50 Hz / hertz AO P2.4. b,c the supply is alternating current allow the current changes direction 50 times per second f 2 marks 3(c) allow mark f 230 x 0.3 provided no subsequent step 2 AO2 P2.4.2 c 3(d) A most efficient no mark f selection AO3 P2.4 allow less energy used / input f the same output allow lowest power input f the same output allow cheapest to run f the same output igne cheapest Total 0 9 of 9

10 MARK SCHEME GCSE ADDITIONAL SCIENCE (ROUTE 2) AS2HP JUNE 205 Question Answers Extra infmation Mark 4(a) any two from: (anaerobic respiration) f first 3 bullet points assume comparison if not stated allow converse if clearly referring to aerobic respiration 2 AO B2.6. b/e B2.6.2 b/c does not use oxygen (but aerobic does) allow (anaerobic) causes (muscle) fatigue does not produce carbon dioxide (but aerobic does) does not produce water (but aerobic does) releases less energy do not allow no energy released do not allow less energy produced do not allow references to use of glucose as a difference 4(b)(i) glycogen crect spelling required AO sted in muscles allow stage in liver / cells B2.6.i allow fat sted in muscles / liver / cells converted / broken down (to glucose) allow fat is converted (to glucose) allow glucagon (converts glycogen to glucose) if no other mark awarded allow glucose absbed from (small) intestine / digestive system f mark starch sted in muscles / liver / cells converted (to glucose) f mark 0 of 9

11 MARK SCHEME GCSE ADDITIONAL SCIENCE (ROUTE 2) AS2HP JUNE 205 4(b)(ii) (amount of) oxygen needed to oxidise lactic acid allow remove / break down f oxidise allow (amount of) oxygen needed to convert lactic acid into carbon dioxide and water AO B2.6.2 a/b/c Total 6 of 9

12 MARK SCHEME GCSE ADDITIONAL SCIENCE (ROUTE 2) AS2HP JUNE 205 Question Answers Extra infmation Mark 5(a) Number of times the cell divides Mitosis Meiosis / once 2 / twice one mark f each crect row if no rows are crect award mark f a crect column 3 AO B2.7. a/c/e/g/h B2.7.2 b Number of cells fmed Number of chromosomes in each of the cell fmed in humans 2 / two 4 / four pairs 23 igne comparative terms such as me / less 5(b) male is XY gets X chromosome (with colourblindness allele) from mother allow male gets Y (chromosome) from father AO2 B2.7.2 a/b B2.7.3 a Total 5 2 of 9

13 MARK SCHEME GCSE ADDITIONAL SCIENCE (ROUTE 2) AS2HP JUNE 205 Question Answers Extra infmation Mark 6(a) any two pairs from: hard parts that do not decay (easily) allow examples of parts of ganisms throughout 4 AO B2.8. a/b parts that do not decay as condition(s) needed f decay are absent eg oxygen is absent parts of ganisms decay (and are) replaced by other materials / minerals burrows / rootlet traces (in soil) (soil) changed into rock parts decay after being surrounded by sediments sediment changed into rock allow reference to trapping by sediments / amber / ice / peat 6(b)(i) idea of change in % / amount of radioactive carbon is greater (per unit time) allow high(er) level of radioactivity in recent fossils AO3 B2.8. d 6(b)(ii) 034 allow mark f.8 x 5730 with no increct answer allow mark f AO2 B2.8. years 6(b)(iii) ganisms were soft bodied allow no hard parts AO so (completely) decayed B2.8. c if no other mark awarded allow mark f (most) fossils / traces destroyed (by geological activity) Total 0 3 of 9

14 MARK SCHEME GCSE ADDITIONAL SCIENCE (ROUTE 2) AS2HP JUNE 205 Question Answers Extra infmation Mark 7(a) 2H 2 O 2 2H 2 O + O 2 products may be in either der allow crect multiples f balancing award mark f crect fmulae with an arrow drawn after H 2 O 2 igne silver / catalyst / heat written on the arrow 2 AO2 C2.4 7(b) increases surface area which gives me frequent collisions allow (so) increased probability of collisions AO, AO2 C2.4.f/g (so) rate (of reaction / decomposition) is increased 7(c) any two from: igne references to volume of hydrogen peroxide 2 AO3 C2.4.g mass of catalyst concentration of hydrogen peroxide allow particle size of catalyst allow amount of catalyst allow mass / amount of manganese (IV) oxide and lead (IV) oxide temperature (of hydrogen peroxide) 7(d)(i) steeper (initial) gradient levels off sooner allow reaction is faster allow reaction finishes earlier AO3 C2.4.a/g allow f 2 marks produces the same volume of gas me quickly 7(d)(ii) (because) same volume of hydrogen peroxide used AO2, AO3 C2.4.a/g (and) catalyst has no effect on amount of product the catalyst is not used up (during the reaction) Total 4 of 9

15 MARK SCHEME GCSE ADDITIONAL SCIENCE (ROUTE 2) AS2HP JUNE 205 Question Answers Extra infmation Mark 8(a) large amount of electricity needed f process allow large amount of energy needed f the process AO3 C2.7.b/h allow smaller energy losses during transmission 8(b) (mixture) melts at lower temperature allow lowers the melting point (of the mixture) AO C2.7.a/h (so) less energy is required allow less heat / electricity is required allow (so) the process is cheaper 8(c)(i) 2O 2- O 2 + 4e - AO2 C2.7.g 8(c)(ii) carbon / (positive) electrode reacts with oxygen to fm carbon dioxide (so) electrode wears away AO, AO3 C2.7.h 8(d) any three from: (aluminium ions) are positive where (ions) gain electrons where (ions) are reduced allow Al 3+ (ions) 3 AO, AO2 C2.7.a/b/ c/e (gain) 3 (electrons) (so) fming aluminium atoms Total 0 5 of 9

16 MARK SCHEME GCSE ADDITIONAL SCIENCE (ROUTE 2) AS2HP JUNE 205 Question Answers Extra infmation Mark 9(a)(i) (different) number of neutrons allow fewer neutrons has only neutron AO P2.5. e allow different mass (deuterium has) a lower mass 9(a)(ii) (same) number of protons allow (both) positive / + / H + both have proton have the same charge AO P2.5. e 9(b)(i) (the) mass of the Sun is very large igne the Sun is very large AO2 P2.6.2 b / f (and only a) small proption of the mass is converted (to energy) each year allow 2 marks f calculation of 2 x 0 4 years 9(b)(ii) igne reference to supernova as a stage AO P2.6.2 e black hole neutron star 9(b)(iii) elements heavier than iron are fmed in a supernova AO P2.6.2 f (and) Earth is fmed from a supernova (explosion) Total 8 6 of 9

17 MARK SCHEME GCSE ADDITIONAL SCIENCE (ROUTE 2) AS2HP JUNE 205 Question Answers Extra infmation Mark 0(a) 4.5 x AO2 P2.4.2 d allow mark f crect substitution. ie 3.0 x 0 7 x x 5 provided no subsequent step 0(b) gets hot igne references to melting AO P2.4.2 a 0(c) any one from: doesn t last long enough p.d. / voltage / charge / current too high not a.c. AO3 P2.4. a, c can t predict where / when it will strike allow it is unreliable difficult / impossible to ste Total 4 7 of 9

18 MARK SCHEME GCSE ADDITIONAL SCIENCE (ROUTE 2) AS2HP JUNE 205 Question Answers Extra infmation Mark (a) any one from: helium nucleus allow 4 2 He2+ P2.5.2 c AO 2 protons and 2 neutrons (b) a few cm igne not very far allow any value above 0 and up to 0 cm AO P2.5.2 e (c)(i) (radon is likely to be) breathed in (radon / alpha radiation is) dangerous / harmful inside the body allow radon accumulates in the house allow particles f radiation AO AO2 P2.5 / e alpha radiation is ionising causes (named) cancer allow causes mutations damages DNA / cells (c)(ii) any three from: radiation is random different rooms may have different levels 3 AO3 P2.5 using two detects leads to a mean reading needs 3 months to account f variations / anomalies 3 months is long enough to detect a measurable amount allow average f mean allow needs three months to get mean / average readings if marking points three and four are not given, allow mark f mean / average Total 8 8 of 9

19 MARK SCHEME GCSE ADDITIONAL SCIENCE (ROUTE 2) AS2HP JUNE of 9