Additional Sample Mark Scheme GCSE Science 2011

Transcription

1 ` Additional Sample Mark Scheme GCSE Science 2011 GCSE GCSE Physics () Edexcel Limited. Registered in England and Wales No Registered Office: One90 High Holborn, London WC1V 7BH

2 General Marking Guidance All candidates must receive the same treatment. Examiners must mark the first candidate in exactly the same way as they mark the last. Mark schemes should be applied positively. Candidates must be rewarded for what they have shown they can do rather than penalised for omissions. Examiners should mark according to the mark scheme not according to their perception of where the grade boundaries may lie. There is no ceiling on achievement. All marks on the mark scheme should be used appropriately. All the marks on the mark scheme are designed to be awarded. Examiners should always award full marks if deserved, i.e. if the answer matches the mark scheme. Examiners should also be prepared to award zero marks if the candidate s response is not worthy of credit according to the mark scheme. For questions worth more than one mark, the answer column shows how partial credit can be allocated. This has been done by the inclusion of part marks eg. Where some judgement is required, mark schemes will provide the principles by which marks will be awarded and exemplification may be limited. When examiners are in doubt regarding the application of the mark scheme to a candidate s response, the team leader must be consulted. Crossed out work should be marked UNLESS the candidate has replaced it with an alternative response. Quality of Written Communication s which involve the writing of continuous prose will expect candidates to: Write legibly, with accurate spelling, grammar and punctuation in order to make the meaning clear Select and use a form and style of writing appropriate to purpose and to complex subject matter Organise information clearly and coherently, using specialist vocabulary when appropriate. Full marks will be awarded if the candidate has demonstrated the above abilities. s where QWC is likely to be particularly important are indicated (QWC) in the mark scheme, but this does not preclude others.

3 General Information The following symbols are used in the mark schemes for all questions: eq / oblique Symbol Meaning of symbol Indicates that credit should be given for other correct alternatives to a word or statement Words or phrases separated by an oblique are alternatives to each other { } curly brackets ( ) round brackets Indicate the beginning and end of a list of alternatives (separated by obliques) where necessary to avoid confusion Words inside round brackets are to aid understanding of the marking point but are not required to award the point

4 1(a) B 1(b) An explanation linking the following points some are absorbed by bone rest pass through (to photo plate) (2) 1(c)(i) An explanation linking the following points OR each X-ray slice corresponds to a 2-D picture (which) the scan puts next to each other in order like a loaf a loaf of bread consists of parallel slices (which are) arranged next to each other in order like the CAT scan (2) 1(c)(ii) An explanation linking the following points too many X-ray photographs are dangerous (to living tissue) to the body (which) damages the DNA/cells (but) the pliosaur is now dead/will not be damaged by X-rays (3)

5 2(a) D 2(b) complete table (0) both correct for mark 2(c)(i) plots both points correctly 2(c)(ii) line of best fit 1 2(d) An explanation linking the following points particles will move faster KE will increase (increase in KE is) proportional to temperature in Kelvin Kelvin temperature rise from 293 to 313 by small amount increases by 313/293 or 1.07 (so) KE will increase (slightly) but will not double (4)

6 3(a) B 3(b) charge momentum (2) 3(c) momentum conserved in both KE only conserved in elastic collision (2) 3(d) equation showing conservation of momentum allow substitution and transposition in either order substitution m p u p = m h v h + m p v p or words transposition 2.2 x 10 7 = m h p h x x 10 7 = momentum of helium nucleus evaluation 4 x v = 3.5 x 10 7 v = 8.75 x 10 7 (m/s) give full marks for correct answer, no working (3)

7 3(e) substitution 1.6 x x V = ½ x 9.1 x x (4.0 x 10 7 ) 2 allow substitution and transposition in either order transposition V = ½ x 9.1 x x (4.0 x 10 7 ) x evaluation approx 4500 (V) give full marks for correct answer, no working (3)

8 4(a) C 4 (b) An explanation linking the following points u + u + d (gives) +2/3e +2/3e -1/3e = +1e (2) 4(c) one-third (of the mass of a proton)

9 Indicative Content QWC *4(d) A discussion including some of the following points Mark Similarities and differences of processes: both emissions come from the nucleus emitted randomly causes a neutron to become a proton and vice versa Similarities and differences of quark behaviour: Beta minus emission only neutron has the quarks d+d+u one of the downs changes (flavour) and becomes an up an electron is emitted the neutron becomes a proton the proton produced has quarks d+u+u Beta plus emission only proton has quarks d+u+u one of the ups changes (flavour) and becomes a down a positron is emitted the proton becomes a neutron the neutron produced has quarks d+d+u (6) Level 0 No rewardable content a limited discusion of a single process, a similarity or a difference the answer communicates ideas using simple language and uses limited scientific terminology spelling, punctuation and grammar are used with limited accuracy some discusion of both processes or a full discussion of one processs with some similarity or difference the answer communicates ideas showing some evidence of clarity and organisation and uses scientific terminology appropriately spelling, punctuation and grammar are used with some accuracy a detailed discussion of both processes including both similarities and differences the answer communicates ideas clearly and coherently uses a range of scientific terminology accurately spelling, punctuation and grammar are used with few errors

10 5(a) (i) C 5(a) (ii) any integer greater than 19 but not equal to (2) 5(a) (iii) All four numbers correct 2 marks. Two or three correct 1 mark. 40 (Ca) (Ar) (2) 5(b) An explanation linking the following points a proton becomes a neutron (so) Z decreases by 1 and so N increases by 1 so will approach line of stability from below and right (so) just below the curve (and for nuclei with low number of protons) Z 1, N + 1 circle on diagram in appropriate place (3)

11 5(c) K + e with numbers correct balancing 40 K e numbers correct, 2 marks 3 numbers correct, 1 mark (Ar) (3)

12 6 (a)(i) D 6 (a)(ii) transposition sin30/1.5 allow substitution and transposition in either order substitution 0.33 evaluation < 0.34 about 19.5 give full marks for correct answer, no working (3) 6 (b) angle of incidence for which angle of refraction is 90 for which the refracted ray goes along the boundary or above which ALL light is reflected internally (2)

13 Indicative Content QWC *6(c) An explanation linking some of factors within diagram 1 and some of the factors within diagram 2 Mark Diagram 1 angle of incidence (45 ) is greater than critical angle (42 ) so total internal reflection occurs angle of incidence =angle of reflection so ray turns through 90 and leaves prism through ZY Diagram 2 partial reflection (which is) 90 to incident ray (partial) refraction into glass towards normal angle of refraction less than 45 angle of refraction is (just over) 28 leaves prism through XZ Up to a maximum of 3 marks can be scored using labelled diagrams only (6) Level 0 No rewardable content the explanation is limited to a single effect on one diagram the answer communicates ideas using simple language and uses limited scientific terminology spelling, punctuation and grammar are used with limited accuracy some explanation for both diagrams or a full explanation of one. Some consideration is given to numerical values the answer communicates ideas showing some evidence of clarity and organisation and uses scientific terminology appropriately spelling, punctuation and grammar are used with some accuracy the explanation will be clear and precise. Numerical values will be considered particularly for the total deviation for TIR and the angle of refraction the answer communicates ideas clearly and coherently uses a range of scientific terminology accurately spelling, punctuation and grammar are used with few errors