GCSE MARKING SCHEME SCIENCE PHYSICS (LEGACY)

Transcription

1 GCSE MARKING SCHEME SCIENCE PHYSICS (LEGACY) JANUARY 0

2 INTRODUCTION The marking schemes which follow were those used by WJEC for the January 0 examination in GCSE SCIENCE PHYSICS (LEGACY). They were finalised after detailed discussion at examiners' conferences by all the examiners involved in the assessment. The conferences were held shortly after the papers were taken so that reference could be made to the full range of candidates' responses, with photocopied scripts forming the basis of discussion. The aim of the conferences was to ensure that the marking schemes were interpreted and applied in the same way by all examiners. It is hoped that this information will be of assistance to centres but it is recognised at the same time that, without the benefit of participation in the examiners' conferences, teachers may have different views on certain matters of detail or interpretation. WJEC regrets that it cannot enter into any discussion or correspondence about these marking schemes. Unit Page Physics (Legacy) Foundation Tier Physics (Legacy) Higher Tier Physics (Legacy) Foundation Tier 7 Physics (Legacy) Higher Tier 0

3 PHYSICS (LEGACY) FOUNDATION TIER Question. Line from to Radiation Line from to Conduction Line from to Convection Line from to Radiation. (a) 00 0 = 80 () (b) 0 00 = 80(%) 00 Subs () Ans () allow e.c.f. (0.8 award mark). (a) (i) 86 = 0 () (ii) Cost = 0 0 Subs / Ans () allow e.c.f. = 9000 p = ( )90 Conversion to () (b) (9000) = ( )/ (00) Subs () Ans () allow e.c.f. (a) (i) 8 (m/s) () (ii) v 8 f = = = or 0. (Hz) Subs () Ans () allow e.c.f. λ 0 (b) Speed m/s / slower () Freq 0. Hz / greater () Or speed different () Frequency different (). Disposal of waste Contamination of the water used for cooling Decommissioning time Meltdown / explosion Safety needs to be qualified Transport of fuel to and from for reprocessing Risk of terrorist attack Pollution needs to be qualified e.g. risk of leaks Any ( )

4 6. (a) Fusion () Hydrogen to Helium / light elements to heavier elements () (b) (i) Explosion of a star () (ii) Stars of a high mass / big enough star () 7. (a) (i) Electricity (ii) Has best value for cost per MJ / gets more energy for 0 p (b) (i) Cost of gas = /00(p) () (ii) Number of MJ = 800 (MJ) () (iii) Cost using coal = 8/800 (p) () allow e.c.f. 8. (a) Venus (b) Highest temperature () even though further from the Sun than Mercury / even though not the nearest planet to the Sun() (c) Subs () 96 million km [Answer () Unit ()] Unit must match answer 6 9. (a) Radio waves in st LH box or X-rays in RH box () Correct sequence for remaining parts () (b) Remote (controls), thermal imaging, optical fibres, radiant heaters, burgular alarms, grilling/toasting, mobile phones Night lights, Heat treatment Any ( ) (c) X-rays ionises [molecules in] cells / damages DNA / mutates cells ()

5 0. (a) To maintain supply to customers when a breakdown occurs / changes in demand (b) (i) [Low resistance] to keep heat loss to minimum (ii) High voltages are dangerous / stop people being eletrocuted / people can t touch them / can t get damaged (c) Step- up to raise voltage (to a suitable level) () ( for transmission) with minimum loss of energy () Step-down to lower voltage to safe value for domestic use () Statement of value correctly used in transmission or domestic use, e.g. 000 V, V 0[accept 0 ] V () Award a maximum of marks only for (b) and (c) 6. (a) (i) 800 (W) (ii) = 8000 (J) Or = 0.8 x 60 = 8 kj Subs () Ans () allow e.c.f. (b) This is the frequency of the radiation used / or correct definition of frequency

6 HIGHER TIER Question. (a) Radio waves in st LH box or X-rays in RH box () Correct sequence for remaining parts () (b) Remote (controls), thermal imaging, optical fibres, radiant heaters, burgular alarms, grilling/toasting, mobile phones Night lights, Heat treatment Any ( ) (c) X-rays ionises [molecules in] cells / damages DNA /mutates cells (). (a) To maintain supply to customers when a breakdown occurs / changes in demand (b) (i) [Low resistance] to keep heat loss to minimum (ii) High voltages are dangerous / stop people being eletrocuted / people can t touch them / can t get damaged (c) Step- up to raise voltage (to a suitable level) () ( for transmission) with minimum loss of energy () Step-down to lower voltage to safe value for domestic use () Statement of value correctly used in transmission or domestic use, e.g. 000 V, V 0[accept 0 ] V () Award a maximum of marks only for (b) and (c). (a) (i) 800 (W) (ii) = 8000 (J) Or = 0.8 x 60 = 8 kj Subs () Ans () allow e.c.f. (b) This is the frequency of the radiation used / or correct definition of frequency (c) Wave speed = wavelength frequency [ accept v = fλ] 6 Use of Hz [or equiv] i.e. conversion () 8 0 λ = = 0. (m) Substitution () Manipulation with formula or numbers () (x0 8 award mark only) 0 8

7 . (a) (i) = (W) / 0 MW / kw (ii) Useful power [transfer] % Efficiency = 00 Total power [input] = 00 substitution () input power Input = 6.7 M(W) / (W) / 7 M(W) manipulation from formula or numbers() answer () allow e.c.f. (b) (i) Less demand for electricity at night or by implication (ii) Heat is also given to the water in pumping / reference to efficiency of pumps (c) Low start-up time so instant energy to grid [need reference to quickness]() Must reuse water so only a finite amount of energy can be generated each day.() 9. (a) (When it runs out of fuel it will expand and cool) to become a red super giant () and then produce a supernova () leaving dense neutron star or black hole () (b) Fusion occurring () with example explained e.g. helium fuses into heavier elements () 6. (a) x 0 8 ( km / year) (b) (i). x 0 8 (km) (ii) time = =.6 (yr) Substitution () Answer () (c) Ceres by value of distance from Sun and an orbit time is between Mars + Jupiter () Temperature 0 (ᵒC) to -00 (ᵒC) () allow e.c.f. from (b)(i) Or some mathematical way of working it out based on the distances of Mars +Jupiter + Ceres from the Sun or on orbital times. ( e.c.f. marks can be obtained from (b)(ii)) (d) Travels more slowly () and has further to go () 8

8 7. (a) (i) Saving = = 00 () Payback = () for substitution = 6 ( yrs) (ii) Costs may increase or decrease, weather may change (colder not hotter) (b) Less power generated Less fuels used Smaller carbon footprint / less greenhouse effect less acid rain Any ( ) (c) Cost = no. of units x cost of unit 60 = no. of units x 0p 60 00() No. of units = = 600 () 0 No. lost through cavity = () 600 = 60 () allow e.c.f. 00 marks available for correct methodology ( is % of 60 award marks) 9 6

9 PHYSICS (LEGACY) FOUNDATION TIER Question. (a) (b) head rest [] (Accept crumple [zone]) crumple [zone] []. (a) 0 (m/s) [] no tolerance (b). (s) [] no tolerance (c) (i) 0 [] = (m/s ) [] (no penalty on negative sign) (ii) line is less steep [] (or equivalent, e.g. in s the speed only decreases by about m/s instead of 6 m/s reference to speed change and time needed in this approach). (a) nucleus [] Accept neutron / accept plurals. (b) (i) 00 [] (ii) or 00 (years) [] (Credit or x 700 where the answer has been miscalculated) Not half lives. (a) The fuse / switch is always in the live wire or it is connected / attached to / contains the fuse/switch [] NOT is closer to the fuse Wire A runs through the fuse - ok (b) OFF [], ON [] (c) current = 0 [ - subs]= 0. (A) [ Ans] (N.B 0/ = 0. gets no credit) (d) current is << Amp / fuse [value] much bigger than current [] ( Do not accept is less than, accept Fuse wouldn t melt before danger of a fire ] A suggested lower value of fuse e.g. A or A Not the current will never get that high (e) Earth [] [Accept: ground] 7 7

10 . (a) (i) stays the same / the same / same [] (ii) bigger / gets bigger [] (iii) stays the same / the same / same [] (b) EITHER: letter W plus arrow downwards [] A plus arrow downwards [] [ OR: Both arrows downwards [] both downward arrows labelled [] nd mark requires st ] NB No requirement for arrows to make contact with ball but need to be within the horizontal extent of the ball. 6. r.c.d. / residual current device [] Accept r.c.b. m.c.b./ miniature circuit breaker [] Accept m.c.d r.c.d. / residual current device [] Accept r.c.b. NB more than answer - s.i.f. 7. (a) emits radiation [or a named form of nuclear radiation] [], which damages [or harms] / ionises cells or causes mutations / cancer [] No credit for reference to exposure. radioactive waves releases radiation (b) cost [ / costly / expensive [], danger of accident on take-off] (do not accept waste falling to earth on its own) [] Accept: can explode [in space and come back to Earth] / collide with space debris (c) (i) long half life / long time to decay [] Answer must relate to the time not corrosion. May be still active ok (ii) It can [or will] leak reference to leakage [accept contamination of water, soil, food chain] [] 6 8. (a) (m) [] (b) (i) 70 (m) [] e.c.f. [ie 8 m answer to (a)] (ii) t = 70(e.c.f.) = [] 7 (s) [i.e ans to (b)(i) 0] 0 8

11 9. (a) correct symbol for voltmeter [accept line through] in parallel with lamp [] (Above or below it ) Accept the voltmeter shown across the lamp / ammeter pair. (b) (i) decreases [] [not slows the current ][ changes not enough] Not dimmer ; accept: the bulb has a lower current through it. (ii) decreases [] (c) (i) cross on coordinate (6,.7) ± ½ division[] reasonably straight line becoming curved after coordinate (,) [] NB line must include origin but don t penalise for lies beyond 8 V. Badly plotted point line mark still possible ecf. No double lines. (ii) 8 [ for.0 in denominator]=.7 (Ω) [Ans ] (Accept.67 or.667 but not [].6,.66 or.666) NB.6, mark] NB.6 dot in the calculation gets the second mark even if the answer line shows.6 only. 0. (a) total radiation [or strength of rad n ] received [] (Accept as a control ) To see if any rad n present To see if any rad n let in without protection Monitor amount of each type of rad n not enough Ref to background radiation Accept: to measure radiation going in [or equiv.] Accept total dose Accept to see how much α / alpha (b) THIRD COLUMN ANSWERS: gamma (only) [], beta & gamma (only)[] (c) 70 [accept 0]. (i) 0000(N)[] [ = (N) [] (No credit for = 6000 N mark (ans)] NB Accept [N] whenever it appears for the first mark ) 7 (ii) [] = 0. (m/s ) [] ( N.B = 0. gets no credit) Totals for foundation paper 0 9

12 HIGHER TIER Question (a) correct symbol for voltmeter [accept line through] in parallel with lamp [] (Above or below it ) Accept the voltmeter shown across the lamp / ammeter pair. (b) (i) decreases [] [not slows the current ][ changes not enough] Not dimmer ; accept: the bulb has a lower current through it. (ii) decreases [] (c) (i) cross on coordinate (6,.7) ± ½ division[] reasonably straight line becoming curved after coordinate (,) [] NB line must include origin but don t penalise for lies beyond 8 V. Badly plotted point line mark still possible ecf. (ii) (iii) 8/.0 [ for.0 in denominator]=.7 (Ohms) [Ans ] (Accept.67 or.667 but not.6,.66 or.666) NB.6, mark] NB.6 dot in the calculation gets the second mark even if the answer line shows.6 only. EITHER: using calculations at early and late points[e.g. from (c)(ii)] [], states that R has increased [] OR Any () from R constant up to V statement that gradient has decreased [after V] states R has increased The resistance of the lamp increases up to V and then increases more slowly 0 marks Rate at which the current increases gets less 9. (a) total radiation [or strength of rad n ] received [] (Accept as a control ) To see if any rad n present To see if any rad n let in without protection Monitor amount of each type of rad n not enough Ref to background radiation (b) THIRD COLUMN ANSWERS: gamma (only) [], beta & gamma (only)[] (c) 70 [accept 0] 0

13 . (a) (i) 0000(N)[] [ = (N) [] No credit for = 6000 N mark (ans)] (ii) [] = 0. (m/s ) [] ( N.B = 0. gets no credit) (b) (c) Any () from mass decreases.. because the fuel used up. resultant force increases weight decreases NB weight decreases because gravity decreases no additional credit. Graph starting at origin sloping upwards with correct curvature [increasing gradient] [], never becoming vertical [] NB Straight sloping line with upward curve [not vertical] at end mark NB Zero initial gradient loses first marking point. 9. (a) m.c.b. / miniature [accept: mini] circuit breaker, [][mcd bod] [] r.c.d./ residual current device, [] [rcb bod] / e.l.c.b. / earth-leakage circuit breaker [] accept earth lead / wire. NB Not just circuit breaker, Not insulated wires / plugs (b) m.c.b breaks the circuit [] because it is faster acting than a fuse[] Faster acting than fuses ok even if referring to rcd. Accept turn off the circuit / more sensitive. Accept fast acting or immediately even if not compared to fuse. (c) Current / electricity flows to earth [] Either Then [accept senses / measures ] there is a difference between the live and neutral currents [] so r.c.d. breaks the circuit [] Or Large current flows because it is a low resistance path [ ] so fuse [melts and] breaks the circuit [ ] Current through the Earth wire / lead ok Large current flows causing fuse to melt mark 7

14 . (a) time taken [] for activity / substance / material / mass / nuclei / atoms to reduce by half [] [Not radioactivity or radiation] accept half the substance the substance / material to decay Not... for the count to decrease by ½ but accept or the count rate to decrease by ½ (b) (i) Strontium : needs to be beta because fewer beta particles pass through thicker aluminium (not just IT IS A BETA EMITTER)[]; it has a [reasonably] long half-life [stand alone] [their choice must have at least years ½ life] [] absorbed if the aluminium is too thick ok / can penetrate a certain thickness of aluminium - ok max (ii) technetium : must be a gamma emitter because it passes out of the body easily / equivalent []AND it has a short [enough] half life [to decay from the body in a short term] [[stand alone but their choice must be technetium or phosphorus] [] Not just ionising. + both sources correct [] (c) (i) decayed radon is continually being replaced [] [however stated, e.g. there is a constant flow of radon [through cracks] ] (ii) subtraction of 0 from 0 = 0 [] Danger factor = 0(ecf) =.6 or 0(ecf) (),.7 ();. ();. () [Ans ] (iii) activity of radon = 0.6 x 00 [] = 0 [Ans ] Total activity = = 0 [Ans ] ecf on 0 from (ii) for first marks: 0.6( ) x 0( ) = 8( ) marks penalty

15 6 (a) (i) 0. x 90 x x [] = 760 (J)[] (ii) PE = 90 x 0 x 6 [] = 00 (J) [] KE = 0. x 90 x = (J)[Ans ] Total energy = 6 (J)[] Allow e.c.f. from error in PE or KE NB use of KE from (i) only first two marks (b) Energy conv to work = = 080 (J) [Ans ] e.c.f.from (a) Force = 080 [] [accept answer to (a)(i) &(ii) e.g. 760 or 6] 8 = 60(N)[] ecf from nd mark 9 Total for higher tier paper 0 GCSE SCIENCE PHYSICS (LEGACY) MS January 0

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