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Radioactivity Mark Scheme 1

Level Edexcel

Subject Physics

Exam Board GCSE(9-1)

Topic Radioactivity

Sub Topic Radioactivity

Booklet Mark Scheme 1

59 minutes

/49

/100

Time Allowed:

Score:

Percentage:

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Question Number

Answer Acceptable answers Mark

1(a) Any one of

Treatment of cancer / radiotherapy

Imaging e.g.: looking at broken bones, tracers

sterilizing (equipment/dressings)

(1)

NOT ultrasound applications/ chemotherapy

accept(to) cure/kill/detect cancer (cells)

accept X-ray(s)/X-ray machine accept PET/CT scans ignore MRI scans

accept (to) kill bacteria

ignore medical treatment and similar vague statements

(1)

Question Number


1(b) 12 hours = 2 half lives (1)

10 (mg) (1)

idea of halving seen e.g. 40 ÷ 2 or 20 (mg) ignore 80 (mg) and 99 ÷ 2

OR

idea of 2 half lives seen or 40/4 OR (6 is 1 half-life and )12 is 2 (half-lives) OR 1/4

Give full marks for correct answer with no working.

(2)


Question Number


1(c)(i) An explanation to include two from:

Radiation is ionising (1)

Radiation can cause specified damage e.g. cancer or damage/mutate DNA (1)

if dose/exposure is too high (1)

(causes) ionisation/ (can) ionise/ mutate cells/tissue

ignore radiation poisoning/death/make you ill ignore {damage/kill} cells/tissue

if absorb(ing) too much (radiation) or so you don’t absorb too much (radiation)

Accept for both marks: Too much radiation can cause cancer (after a while)

(2)

Question Number


1(c)(ii) C we have a better understanding of the risks from radiation (1)

(1)


Question Number

Indicative Content Mark

QWC *1(c)(iii) An explanation including some of the following points

identification of alpha, beta, gamma as possibletypes of radiation

identification of X-rays as possible type of radiation film is dark(er)/changes colour where radiation is

absorbed different areas of the film are exposed to different

types of radiation gamma (or X-rays) affect all areas of film beta absorbed/stopped by aluminium/passes through

paper beta only reaches (top) part of film alpha unlikely to be detected at all the lead will stop (some of) gamma or (some)

gamma will pass through lead/aluminium/paper the paper will stop/absorb alpha

throughout the question accept symbols for types ofradiation

(6)


Total for Question 6 = 12 marks

Level 0 No rewardable content 1 1 - 2 a limited explanation which gives one relevant fact about types

of radiation or the film badgee.g. types of radiation are alpha, beta and gammaOR beta absorbed by aluminiumOR the radiation affects the filmOR gamma can pass through lead

the answer communicates ideas using simple language and useslimited scientific terminology

spelling, punctuation and grammar are used with limitedaccuracy

2 3 - 4 A simple explanation, giving more than one relevant fact abouttypes of radiation OR the film badge OR at least one fact aboutboth.e.g. The 3 types of radiation are alpha, beta and gamma.Gamma can pass through lead.OR The 3 types of radiation are alpha, beta and gamma.Radiation makes the film change colour.OR beta will get through the paper but alpha will be stopped (bypaper).OR Radiation makes the film change colour. The lab. willcompare how much got through the paper, aluminium and lead

the answer communicates ideas showing some evidence ofclarity and organisation and uses scientific terminologyappropriately

spelling, punctuation and grammar are used with some accuracy3 5 - 6 a detailed explanation giving more than two relevant points

about the film badgeOR at least one fact about the types of radiation AND more thanone about the film badgee.g. Beta will get through the paper but alpha will be stopped(by paper).Gamma can penetrate the aluminium.OR The film detects radiation. The aluminium will stop beta but,not gamma.OR The 3 types of radiation are alpha, beta and gamma. Betawill get through the paper but alpha will be stopped (by paper).

the answer communicates ideas clearly and coherently uses arange of scientific terminology accurately

spelling, punctuation and grammar are used with few errors


Question Number


2(a) Three lines as shown:

(2)

Any one line correct only scores 1 mark

(2)

Question Number


2(b) An explanation linking

Absorb (more) neutrons (1)

(to) reduce the number of fission reactions (1)

ignore slow down neutrons

slow down (the rate of) the reaction/fission

(2)

Question Number


2(c)(i) B electrostatic repulsion of protons

(1)

Question Number


2(c)(ii) A description to include

(two/or more/smaller)nuclei combine/fuse/join(1)

(to produce) a largernucleus (1)

{(two or more) hydrogen nuclei/protons OR deuterium and tritium} combine/fuse

(forming) helium nucleus

ONLY penalise use of atoms instead of nuclei ONCE

ignore references to release of energy as this is given earlier in the question.

(2)



Question Number


3 (a)(i) B 21 (1)

Question Number


3 (a)(ii) A (1)

Question Number


3(a)(iii) A description to include any two of

(nucleus/isotope is)unstable (1)

(nucleus/isotope is)radioactive (1)

decay is random (1)

long half life (1)

(2)

Question Number


3(b)(i) 1250 (million years) (1) Between 1200 and 1300 (my) inclusive

(1)

Question Number


3(b)(ii) 2 half lives (1)

2500 (million years) (1) Allow ecf from (bi) Give full marks for answer between 2400 and 2600 with no working.

(2)

K

39

19


Question Number


3(c) An explanation linking any three from

Radon is radioactive (1)

Radon can escape fromrocks and buildings (1)

Radon can be inhaled (1)

Radiation (from radon)can cause cancer (1)

Radon emits alpha (1)

Ignore radiation from rocks themselves

Radon enters/gets trapped in buildings/homes / increases background radiation

(breathed into) lungs

(DNA) mutation / cell damage

(Highly) ionising radiation

(3)



Question Number


4(a) (ii) 12 (1)

Question Number


4(b) B It is very ionising (1)

Question Number


4 (c) gamma (1)

beta (1)

(2)

Question Number


4(d) A decreases by 2decreases by 4

(1)


Question Number


4 (a) (i)

A protons

B neutrons

C electrons

OR A neutrons

B protons

C electrons

(3)


Question Number


5(a) A gamma (1)

Question Number


5 (b)

(1)

An explanation linking the following:-

(it is) ionising (can cause)

damage to tissue/ mutation/cancer/tumours (1)

has high frequency/energy

kill cells / (causes) burns

(2)

Question Number


5(c) Any three from:

keep distant from sources /(stand) in a separate room(behind leaded window etc.)

limit time exposed to theradioactivity

use lead shielding for thesources / handle sourceswith tongs etc. / disposeradioactive material(s) safely

wear lead aprons / usedlead-lined clothing / lead-lined gloves

monitor exposure with somedetector / badge / use of(radiation) meters

(distance also involved if you) use computer controlled equipment

the time aspect must be clear here.

ignore goggles / (special) gloves without detail. Similarly ignore ‘radiation resistant’ (clothes)

(3)


Question Number


QWC 5(d) A description including some of the following points :-

Diagnosis radioactive tracers used in the body to check systems e.g. skeleton / bone, blood flow,

thyroid activity, kidney function. attached to some compound which targets a

particular area of the body radioactive tracers are isotopes with short half-lives

put into the body may go into PET scans, since this involves beta+

emitters gamma cameras, used to detect emissions from

radioactive tracers

Treatment radiotherapy, use of gamma rays (from cobalt 60) /

gamma rays aimed at a tumour to destroycancerous cells. (Use of multiple beams) May causedamage to normal cells.

radioactive inserts placed into the body to destroycancerous cells, mainly used for prostate cancer.

ignore chemotherapy, ultrasound scans, endoscopesetc.

(6)



Level 0 No rewardable content 1 1 - 2 a limited description of one procedure used for either

diagnosis OR treatment e.g. idea of tracers or an elementarynotion of radiotherapy given

the answer communicates ideas using simple language anduses limited scientific terminology


2 3 - 4 a simple description of one procedure used for eitherdiagnosis OR treatment e.g. the tracer emits gamma rayswhich are detected using a gamma camera showing up areaof high uptake / radioactivity; uses radioactive sourcesemitting beta / gamma radiation to destroy cancer cells.


spelling, punctuation and grammar are used with someaccuracy

3 5 - 6 a detailed description a procedure used for diagnosis and a procedure used for treatment. e.g. a short-lived radioactive tracer is injected into the body which then shows up areas of high activity via a gamma camera AND radiotherapy uses gamma to destroy cancer cells in a targeted way, with some detail. PET scanning details acceptable on the diagnosis side. (N.B. The diagnosis aspect may be covered in more detail than the treatment or vice-versa)

the answer communicates ideas clearly and coherently usesa range of scientific terminology accurately




Level Edexcel

Subject Physics


Topic Radioactivity



56 minutes

/46

/100

Time Allowed:

Score:

Percentage:



Question Number


1(a)(i) B a few hours (1)

Question Number


1(a)(ii) An explanation including three of the following: MP1 alpha/the radiation is (highly) ionising (1)

MP2 the radiation destroys cancers/tumours (1)

MP3 alpha particles/ do not penetrate very far in the body/inserted close to the cancer (1)

MP4 half-life is long enough for the treatment to take effect (1)

MP5 half-life is short enough so that the pellets do not need to be removed (1)

kills/ destroys/mutates cells mutates DNA

alpha particles do not/ get out of the organ being treated/ damage cells in other organ

Ignore patients being radioactive Ignore replacement of pellets

(3)

Question Number


1(b) An explanation to include:

reduces the size of tumours/cancers (1)

reduces pain/ relieves symptoms /extends life expectancy / Improves quality of life (1)

stops tumours growing/ slows rate of growth or spread of cancer

(2)


Question Number


1(c)(ii) Justification including:-

appreciation that there would be risks (1)

ONE from:-

non-invasive/ not painful (1) OR more accurate/better/earlier diagnosis (1) OR life-saving/ provide cure (1)

the benefits outweigh the risks/drawbacks/concerns/dangers

gives more useful information

(2)

Total for question 4 = 10 marks

Question Number


1(c)(i) An explanation linking two of the following:-

CT scan lasts much longer / (1) X-ray short exposure

CT scan is many X-ray (slices) (1)

The intensity of radiation for CT scans is higher than for normal X-rays (1)

For CT scan X-ray machine moves (slowly) around the body

many pictures / series of X-rays/ 3D image

(2)


Question Number


2(a)(ii) electron(s) (1)

(1)

Question Number


2(b)(i) evidence of halving activity eg line on graph at 80 (Bq) or two lines at, say, 100 and 50. (1)

8 (days) gains both marks (2)

accept halving in answer space e.g. 160 -> 80 or 80 -> 40or 160 ÷ 2 = 80

NOT 160 ÷ 40 or 131 ÷ {2 or 4} or 40 ÷ 2 (unless clearly an activity)

(2)

Question Number


2(a)(i) proton(s) (1)

NOT photon (1)

Question Number


2(b)(ii) idea of two half-lives (1)

but, 16 (days) gains both marks (2)

halving of 800 twice, e.g. 400 AND 200 seen

Allow ECF from graph eg allow half-life from graph x 2 for both marks (2)


Question Number


QWCC *2( ) A discussion including some of the following points Advantages

- (currently) large resources of fuel/ fuel (reserves) will lasta long time

- (Produces) large amount of (electrical) energy/electricity- Does not produce (much/any) carbon dioxide- Does not produce (much/any) sulphur dioxide- Does not add to global warming/climate change- Good safety record (under normal operating conditions)- Only small amount of fuel needed to produce large amount

of energy/electricity- Reliable supply/provides continuous supply of electricity

(for a long time)- Reduces dependence on foreign supplies of energy

- Conserves fossil fuel supplies- (Spent) fuel can be processed (to produce fuel for other

reactors) - Provides employment/jobs

Disadvantages - Produces nuclear/radioactive {waste/materials}- nuclear/radioactive waste/materials can cause

mutations in DNA/cells/people/animals

- Non- renewable (energy source)- Difficulties in transporting nuclear/radioactive

waste/material - ifficulty in (safely) storing/disposing nuclear

waste/material - Nuclear accidents (can) pollute large areas- Nuclear accidents pollute for a long time- Accept named example of accidents eg Fukishima,

Chernobyl, 3-mile island - Mining and processing fuel both produce large

amounts of carbon dioxide - Expensive to build and/or decommission (nuclear

power stations) - Reference to target for terrorist attacks- Produces material which can be used to develop

nuclear weapons/by terrorists - Negative public perception OWTTE

ignore references such as unsightly, large area needed, noisy as true for most large buildings. Ignore cost of generation or restating stem ie generates electricity or supplies electricity to homes etc.

(6)


(Total for Question 5 =12 marks)

evLevelL No rewardable content 1 1 - 2 • A limited discussion giving one fact

e.g. they give people jobs (in that area)OR they can have accidents like in Japan (after the tsunami).

the answer communicates ideas using simple language and useslimited scientific terminology.

spelling, punctuation and grammar are used with limited accuracy2 3 - 4 A simple discussion that states one advantage and one

disadvantage OR states more than one advantage OR states morethan one disadvantage.e.g. they are a reliable energy source and do not produce any

carbon dioxide.OR they do not cause any global warming as they do not producesulphur dioxide.OR they produce radioactive waste and many people don’t wantthem built.

the answer communicates ideas showing some evidence of clarityand organisation and uses scientific terminology appropriately

spelling, punctuation and grammar are used with some accuracy3 5 - 6 A detailed discussion of either advantages or disadvantages AND

at least a mention of the other one.e.g. They produce large amounts of electricity and don’t produce

carbon dioxide but they produce radioactive materials (in the fuelrods).OR They are a reliable source of energy but they can damage

large areas if there is an accident and the fuel is non-renewable. the answer communicates ideas clearly and coherently uses a

range of scientific terminology accurately spelling, punctuation and grammar are used with few errors


Question Number


3 (a) C - kill microbes in the food (1)

Question Number


3 (b)(i) From the graph Time taken to fall (from 8000) to 4000 (1)

= 5.3 (years) (1)

Any other suitable pair of readings from the graph.

Between 5.1 and 5.5 Full marks for correct answer even if no working is evident

(2)

Question Number


3 (b)(ii) 3 x 5.3

(= 15.9 years)

Allow attempt at extrapolation only if the answer is between 15.5 and 16.5

Allow ecf of 3 half lives from bi. (1)

Question Number


3 (c)(i) Comparison including any two from

Same number of protons (1)

Different number of neutrons (1)

Cobalt-60 is unstable (1)

Same atomic/proton number/charge

Different nucleon number/mass number/atomic mass Cobalt 60 is radioactive

Ignore reference to electrons (2)


Question Number


QWCC *3( )(ii)

A discussion which includes description of the hazards (H) and / or possible precautions (P) to reduce risks arising from them such as

In either option.o Rods are radioactive (H)o Gamma radiation is highly penetrating / ionising

(H)o Radiation from them can cause cancer / damage

to organisms / people / environment (H)o Need for shielding (P)o Security to prevent public access (P)

Transportation / reprocessingo Danger of accident during transport (H)o Need to be suitably protected against damage.

(P)o Danger of interception/high-jacking/terrorists

(H)o Need security (P)o Workers could be exposed to radiation (H)o Special facilities required (P)

Disposalo Can damage environment if not properly

contained (H)o Special disposal facilities, not landfill (P)o Remain radioactive for some time (H)o Need to be kept secure while decaying to safe

levels. (P)o Relatively short half-life means that very long

term storage is not necessary. (P)(6)


(Total for Question 6 = 12 marks)

evLevelL No rewardable content 1 1 - 2 a limited description of hazards or precautions in one option

e.g. The rods are radioactive. Radiation can cause cancer. When therods are disposed of then they will remain radioactive for some time.



2 3 - 4 a simple discussion of hazards for both options or a detaileddiscussion of one option.

A detail discussion may either expand on several descriptivepoints about the hazard or may include suitable precautions.

e.g. The gamma radiation from the rods is highly penetrating. If theywere simply put into landfill then they could damage the environmentand so they would need special storage facilities until they haddecayed to a safe level.



3 5 - 6 a detailed discussion of hazards for both options.e.g. Response as above PLUS if they were transported back to thereactor then they must be in very strong containers so that, if therewas an accident, they would not be damaged and allow radioactivematerial to escape.




Question Number


4(a)(i) Gamma/ γ (wave(s)/ ray(s)/radiation)

X-rays/ radiation(1)

Question Number


4(a)(ii) Any two from It fluoresces (1)

UV (radiation) transfers/gives energy to ink/ink absorbs energy from UV (radiation) (1)

(energy from UV is )(re-)radiated/(re)- emitted by ink at lower frequency/as (visible) light (1)

fluorescent

Ink/it absorbs UV (light/radiation)

Ignore UV is reflected as visible light Ignore luminous

emits visible light

(2)

Question Number


4(b) transposition λ = v/f (1)

substitution

λ = 3 x 108/7 x109 (1)

(1) evaluation 0.043 (m)

Ignore any unit given by candidate

Subst. and transform. either order 1 mark only can be scored for correct substitution after incorrect transposition.

gains 2 3 x 108/7 x109 marks

Accept any number of sig.figs. that rounds to 0.04

(1) 0.04 , 0.0428 (m)

Give full marks for correct answer with no working.

0.04 x any other power of 10 = 2 marks

(3)


Question Number


WC QWCQ A discussion including some of the following points Possible dangerous e-m radiations Microwaves Infrared Ultraviolet (UV) X-raysgamma rays

Correctly linked to Internal heating of body cells (microwaves) Skin burns (infrared) Damages skin cells/sunburn (UV) Damages eyes (UV) Can cause skin cancer (UV) Can cause cataracts (UV) Damage to cells inside the body( X-rays) Mutate/ kill cells in the body (gamma) Damages DNA (X-rays and gamma rays)

Link to frequency As the frequency increases/wavelength decreases (microwave -> gamma) the waves become more penetrating and do more damage/danger as they have more energy.

(6)

Level

0 No rewardable content

1 1 - 2 • a limited description e.g. gives at least 2 correct radiations and linksboth to correct damage OR at least 2 correct radiations named withlink to correct damage from one and idea that frequency is linked todamage OR just has link between higher frequency and moredamage/dangerous e.g. infrared burns your skin and X-rays candamage cells. OR X-rays have a higher frequency than microwavesand can cause cancer OR Higher frequencies cause more damage tocells.

• the answer communicates ideas using simple language and useslimited scientific terminology

• spelling, punctuation and grammar are used with limited accuracy2 3 - 4 • a simple description e.g. gives most of the correct radiations and links

to correct damage, at least one with detail of the damage that iscaused OR links two to detail of the damage, AND has a link betweenfrequency and energy/danger e.g. Microwaves are absorbed by waterin body cells. UV can cause skin cancer and damages your eyes. X-rays and gamma rays can damage cells inside your body OR Gammaand X-rays can penetrate deep into the body. Gamma does mostdamage as it has the highest frequency.

• the answer communicates ideas showing some evidence of clarity andorganisation and uses scientific terminology appropriately

• spelling, punctuation and grammar are used with some accuracy3 5 - 6 • a detailed description e.g. gives most of the correct radiations with

links to detail of the damage AND explains the link between frequency


and energy/danger. e.g Microwaves heat up the water in cells. UV can cause cataracts. Gamma rays are the most penetrating and can mutate cells inside the body because they have the highest frequency.

• The answer communicates ideas clearly and coherently uses a rangeof scientific terminology accurately

• spelling, punctuation and grammar are used with few errors



Level Edexcel

Subject Physics


Topic Radioactivity



56 minutes

/46

/100

Time Allowed:

Score:

Percentage:



Question Number

Answer Acceptable answers

Mark

1(a) one mark for each correct line

(4)

Question Number


1(b) D (1)

Question Number


1(c) B becquerel (1)

Question Number


1(d) A description including any two from: • secure storage (1)

• avoid direct contact (1)

• wear protective clothing (1)

• minimise exposure (1)

• shielding (1)

• minimise dose (1)• monitor exposure (1)

• protect other people (1)

either the purpose, such as to prevent radiation getting out or a description such as lead-lined box/locked away when not in use. do not touch / use tongs /wash after handling

lead lined suits/aprons/masks/gloves ignore goggles

long distance away / not pointing towards body/

keep sources shielded /stand behind shields short time wear film badge/use Geiger counter (to monitor radiation levels) warning signs / barriers / restricted areas /controlled areas

(2)

alpha

beta

gamma

sterilisation of medical equipment

household fire (smoke) alarm

irradiating food

gauging thickness of cardboard


Question Number


2(a) P and M

OR M and P

OR N and Q

OR Q and N

one mark for a pair

(1)

Question Number


2(b) {atomic /proton} number drops by 2 and {mass/nucleon} number by 4 (1)

(which is) alpha decay (1)

2 protons and 2 neutrons are lost 92 90 and 238 234

helium nucleus given off (which is) alpha particle

(2)

Question Number


2(c) same {mass/nucleon} number but {atomic/proton} number increases by 1 (1)

(negative) beta decay (1)

a neutron changes to a proton

ignore GAINS a proton

beta particle /electron given off (2)

Question Number


2(d)(i) alpha Alpha ray, alpha particle, α Ignore capital letters

(1)

Question Number


2(d)(ii) A description including two of

one increases as other increases (1)

rate of increase is in the range from 1.17 to 1.33 (cm/MeV) (1)

range gradually increases more with energy (1)

the particles with higher energy travel further accept values quoted from graph

not (quite) linear/not proportional /curves upwards accept values quoted from graph

(2)


Question Number


2(e) chain reaction needs a neutron from one fission to reach another uranium nucleus/atom (at the right speed) (1)

(fission of 238) needs {fast/high(er) energy} neutrons (1)

idea of continuous nature of chain reaction

the neutrons would be going too slowly /do not have enough energy / lose energy too fast

(2)


Question Number


3(c)i 1.9-2 (days) (1)

Question Number


3(c)ii

plotting (0,40), (2,20 ) and (4,10) OR ANY line which passes through those coordinates (1)

smooth curve through those points (1)

Ignore any part of line after 4 days

(2)

Question Number


3(a) A description to include • name of detector / move

detector over the ground(1)

• where leak is, there will bean increased rate (1 )

(move) until a {leak/high reading} is found (2)

Question Number


3(b) D It is the time it takes for half the atoms to decay (1)


Question Number


QWCQWC * ) An explanation including some of the following ideas

Need for measurement (N)

Background radiation • is {always present/all around us}

• has (natural) source(s) exemplified by space, livingthings, rocks, food, nuclear/medical sources etc.

• would give false reading in experiment

How and why to measure(H) Background radiation measurement

• is taken at site of experiment because it is different indifferent places

• is taken with all apparatus except source in place

• is taken before and after because {it can change withtime / they need an average}

• {must be worked out for same time as (or longer than)experiment / rate found} so analysis is simpler

• It is {taken several times/ averaged} because it israndom

Analysis (A) Background radiation measurement

• must be subtracted from {measurements with source/main count rate}

(6)

0 Level No rewardable content 1 1 - 2 • A limited explanation mentioning any two from N or one from H

or Ae.g. Background comes from space and rocks.(N) It is there all the

time. (N) OR Readings for background must be repeated because they are

random. (H) OR Background must be taken away from all other readings (A) • the answer communicates ideas using simple language and uses

limited scientific terminology• spelling, punctuation and grammar are used with limited

accuracy2 3 - 4 • A simple explanation linking aspects of two ideas i.e. N + H

OR N + A OR H + Ae.g Take readings without source (H) and subtract them from the

main readings with source present.(A)OR It should be taken several times because it is random (H)so that

the average can be subtracted from the main readings (A) • 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


3 5 - 6 • A detailed explanation linking A with EITHER N + an ideafrom H

OR two or more ideas from H

e.g.Background radiation is there all the time. (N) You need to takereadings at the place where you will do the experiment and with all the apparatus set up except the source because BR changes from place to place.(H) Then you should subtract background readings from the main experimental readings.(A)

OR Take several readings of count rate for averaging since the effect is random (H) and make sure that they are taken in the same place.(H) Then subtract from readings in main experiment.(A)

• the answer communicates ideas clearly and coherently uses arange of scientific terminology accurately



Question Number


4(a)(i) C the same as the charge on the proton (1)

Question Number


4(a)(ii) A electrons (1)

Question Number


4(b)(i) 222 4 less/4fewer (1)

Question Number


4(b)(ii) 86 2 less/2fewer (1)

Question Number


4(c) A description including two of:

• Kill/damage cells(1)• affecting DNA (1)• (causing) mutation (1)• by ionisation (1)• make cell reproduce

rapidly (1)• cause cancer (1)• (radiation) burns (1)• (radiation) sickness (1) (2)


Question Number


4(d) An explanation linking any suitable precaution to a sensible reason: Eg lead/shielding (1) (because it) stops/absorbs radiation (1)

Use of radiation meters (1) {measure/warn of} radiation received (1)

put up signs (1) (to )keep people away from radiation (1)

increasing distance (1) (to)reduce intensity (1)

to reduce dose(1) by limiting the number of X-rays taken (1)

source locked away for shielding

(worker) leaves room inverse square law

(2)

Total mark question 1= 8


Question Number


5(a)(i) B highest frequency (1)

Question Number


5(a)(ii) D positively charged (1)

Question Number


5(a)(iii) an explanation linking: • (when) the filament is

{heated/very hot} (1)

with one of: • electrons escape (have

enough energy) (1)

• electrons escape from thesurface (1)

cathode / metal (for filament)

released

accept boil off

IGNORE produces / emits (2)

Question Number


5(a)(iv) a suggestion that electrons do not reach target

otherwise electrons collide with (air) particles electrons are absorbed electrons ionise air stops electrons reaching target

(1)

Question Number


5(b) transposition 2 x e x V/ m = v2 (1)

substitution v2 = 2 x 1.6 x 10-19 x 40 000/9.1 x10-31

(1) evaluation of v 1.2 x 108 (m/s) (1)

Either order ignore powers of ten

until evaluation

give full marks for correct answer, no working accept 1.19 ×108

(3)



Level Edexcel

Subject Physics


Topic Radioactivity



58 minutes

/48

/100

Time Allowed:

Score:

Percentage:



Question Number


1(a)(i) 27 (1)

33 (1)

accept 33

27

for 1 mark (2)

Question Number


1(a)(ii) an electron (1)

Question Number


1(a)(iii) A description including three of the following points

• beta (radiation) is electron(s)(1)

• beta has mass (1)

• beta has (negative) charge (1)

• beta is a better ioniser (1)

• beta is less penetrating (1)

• gamma radiation iselectromagnetic (1)

• wave (1)

• gamma travels at a speed oflight (1)

• gamma is just energy (1)

Allow ORA where applicable

allow em for electromagnetic

ignore uses (3)


Question Number


QWC *1(b) A description including some of the following points

Similarities (S): • involve nuclei• involve particles colliding• energy released• can cause explosions/rapid release of energy

Differences (D):

Fission • splitting• of heavy nucleus• by neutron• chain reaction• products radioactive• used in power stations at present• rate can be controlled

Fusion • joining smaller nuclei• to form larger nucleus• occurs in stars• needs very high temperature and/or pressure and/or

particle density• because of like charge repulsion (6)

Level 0 No rewardable content 1 1 - 2 • a limited description including a similarity OR a difference

e.g. (S) both release energyOR (D) one is splitting, one is joining.


• spelling, punctuation and grammar are used with limited accuracy2 3 - 4 • a simple description including EITHER one similarity AND one

differenceOR some differences / similaritiese.g.(S) both give out energy but (D) fission uses uranium, fusionuses hydrogen.OR (D)fusion occurs in stars when hydrogen particles joinOR (S) both involve nuclei and release energy

• the answer communicates ideas showing some evidence of clarityand organisation and uses scientific terminology appropriately

• spelling, punctuation and grammar are used with some accuracy3 5 - 6 • a detailed description including EITHER two similarities (or one

detailed) AND one difference OR one similarity and two differences(or one detailed) e.g. (S) uranium gives out energy (D) when it ishit by neutrons and energy is released (D) in fusion when (small)nuclei join.

• the answer communicates ideas clearly and coherently uses a rangeof scientific terminology accurately



Question Number


2(a)(i) Any one from the following

• living things (1)

• space (1)

• nuclear powerstations/accidents (1)

• hospitals (1)

• industrial processes (1)

Ignore radon gas from …

another radioactive rock

a named radioactive substance eg uranium, radium, plutonium

(1)

Question Number


2(a)(ii) statement 2 only (1)

Question Number


2(b) A description of a change including the following points

• used to be thought beneficial(1)

• now known to be extremely{dangerous/hazardous} (1)

{was commonly used (without care)/dangers were not realised}

now known to cause cancer

now can be used safely {under controlled conditions/medical supervision}

(2)

Question Number


2(a)(iii) An explanation linking two of the following points

• radon gas comes from rocks(1)

• types of rocks vary in differentparts of the UK (1)

• where there is more (of this typeof) rock, the reading is higher (1)

may be explained in terms of specific places eg Cornwall

(2)


Question Number


QWC *2(c) A discussion including some of the following points

Appropriate type of radiation is chosen - some passes through- – β and γ not α- significant change with thickness- - β

Half-life - reference to half-life- not too long - too much material needed for activity- not too short – expense of replacing regularly- disposal problems

Safety issues - shielding

• type of radiation• linked to appropriate material and thickness

- security• storage of spares• in use

- safety procedures / precautions in use (6)

Level 0 No rewardable content 1 1 - 2 • a limited discussion of one factor with no reasons e.g.(F)

penetration / half-life/ safety.• the answer communicates ideas using simple language and uses

limited scientific terminology• spelling, punctuation and grammar are used with limited accuracy

2 3 - 4 • a discussion linking some of one factor (F) with some reasoning (R)OR two factors e.g. (F) use a source which has a long/short halflife (R) with suitable reason OR (F) use radiation which is affectedby different thicknesses of paper and (F) mention of half-life.


• spelling, punctuation and grammar are used with some accuracy3 5 - 6 • a detailed discussion of at least two factors with some reasons e.g.

(F)F se a (beta) radiation which is affected by thickness (R)because others will not penetrate at all (alpha) or will not be{affected / stopped} by paper (gamma) and (F) some discussion ofhalf-life or safety.




Question Number


3(a) An explanation linking the following points

• small percentage / amount ofmaterial (1)

• activity level low / less thanbackground (1)

radiation/radioactivity for activity within safe limits (2)

Question Number


3(b)(i) B 50 days (1)

Question Number


3(b)(ii) 12.5 10 - 15(1)

Question Number


3(c) An explanation linking the following points

• time for halving (1)

• clear as to what is halving(1) Allow for atoms: isotope /

element / nuclei / (radioactive) substance /particles/(radioactive) material/radiation/count rate/Bq/activity/radioactivity

time for half of the atoms to decay (2)

time for the activity/count rate to drop to half (of original value) (2)

time for ½ of it to decay (1) (2)


Question Number


QWC *3(d) A discussion including some of the following points

Model components related to actual machine • lamp – radioactive source (β- source)• sensor (LDR) – Geiger counter arrangement• card – liquid in bottle

Interaction of components related to working of machine • rising of card - more liquid in bottle• rising of card – less light

– higher resistance– smaller current / reading– circuit switches on if too much light

• greater absorption gives less radiation to detect• machine discards bottle if too little liquid, model does not

(6)

Level 0 No rewardable content 1 1 - 2 • a limited discussion comparing some of the indicative content. E.g.

two of the lamp, sensor and card are related to the source (Geiger)counter and liquid respectively.


• spelling, punctuation and grammar are used with limited accuracy2 3 - 4 • a simple discussion comparing parts of the process. E.g. Two of the

lamp, sensor and card are related to the source Geiger counter andliquid respectively. The rising of the card gives more liquid in thebottle.


• spelling, punctuation and grammar are used with some accuracy3 5 - 6 • a detailed discussion of the whole process. E.g. the lamp, sensor

and card are related to the source Geiger counter and liquidrespectively. The rising of the card gives more liquid in bottle. Toomuch light/ radiation getting through starts the alarm.




Question Number


4(a)(i) any one of X-ray (machines) / smokealarms/ nuclear/ radioactive waste (1)

nuclear weapons (tests) nuclear power plants (medical) tracers/technetium

(1)

Question Number


4(a)(ii) an explanation linking: comes from granite / rocks (1) none/ less of these (rocks) in some areas (1) in some

areas/Cornwall/Aberdeen

the second mark is dependent on the first.

(2)

Question Number


4(b)(i) suitable lines on graph to show halving after about 200 000 years (2)

• horizontal line at 7 0 +or –50Bq on y-axis to curve (1)

•meeting (by eye) vertical linefrom x-axis between 190,000years and 230,000 years (1)

use of data from graph to show halving after about 200 000 years

1500/2 =750(Bq) or 1600/2=800(Bq)

gives a half-life of 210,000 +or- 20 000 (years)

(2)

Question Number


4(b)(ii) any one of

• penetrates/passes throughthe skin (1)

• ionises (1)• damages tissue/ cells/DNA (1)• mutates cells/DNA(1)• causes cancer(1)

(1)

Total marks for question 5 = 12


Question Number


QWCQWC * ) an explanation which may include some of the following points:

properties of nuclear waste radioactivity is dangerous some isotopes in nuclear waste have long half-lives/radioactive for thousands of years products of fission are warm identified radiation from nuclear waste e.g alpha, beta, gamma

problems caused by nuclear waste leakage of radioactivity contamination of ground/sea water/lakes /rivers contamination of crops/fish/animals/drinking water harm to humans/cancer/radiation poisoning/ damage to cells/mutation of cells or DNA difficulty in transporting safely/ stolen by terrorists fears of local people

solutions for dealing with nuclear waste safely long term storage, underground /under the sea radiation shielding, lead/steel/concrete/ containers, sealed in glass. human safety, radiation suits, using tongs/lead jackets safe location, away from people/remote areas/sea cooling, ponds information to persuade local people of safety

(6)

Level 0 No rewardable content 1 1 - 2 • a limited explanation mentioning at least one point, but without

linking, e.g. radioactivity is dangerous ;nuclear waste should be stored underground ;terrorists might steal nuclear waste;


• spelling, punctuation and grammar are used with limitedaccuracy

2 3 - 4 • a simple explanation mentioning two points with an appropriatelinkage e.g. nuclear waste is dangerous and it must be storedunderground ;the isotopes in nuclear waste have long half-lives so they mustbe stored for a long time;


• spelling, punctuation and grammar are used with some accuracy3 5 - 6 • a detailed explanation mentioning a range of points with

appropriate linkagese.g. gamma rays from nuclear waste causes damage to cells so itmust be stored away from where people live ;the isotopes in nuclear waste have long half-lives so they mustbe stored underground or in remote areas;





Level Edexcel

Subject Physics


Topic Radioactivity



59 minutes

/49

/100

Time Allowed:

Score:

Percentage:



Question Number


1(a) A (1)

Question Number


1(b) axes labelled correctly With label or unit (1)

correct shaped smooth curve (1)

line does not reach zero activity (1)

activity / Bq / count rate ignore radioactivity time/ seconds/ any time unit

(3)

Question Number


1(c)(i) Idea of 2 half-lives (1) 11 400 = 2 × 5700

Idea of halving activity twice (1) 0.55 × 2 × 2

Calculation (1) 2.2 (Bq)

11 400 / 5700 = 2

2.2 (Bq) for three marks

(3)

Question Number


1(c)(ii) Explanation linking two of: • Background radiation

affects the measurement (1)

• Needs to be subtractedfrom readings (1)

• Background radiation isvariable (1)

• Background radiationneeds to be averaged (1)

accept interfering / including

varies with place/time/random nature

repeating test improves reliability

(2) t


Question Number


1(c)(iii) One relevant idea: (New method) more accurate (1)

Hard to measure a small activity (1)

Background radiation affects readings (1)

Need to find difference of two small quantities (1)

Can test smaller samples (1)

ignore better method/results / more reliable

difficult to distinguish between the reading and background

(1) grad

Total for question 4=10 marks


Question Number


2(a)(i) Any two of:

Gamma is a wave (1) Alpha is a helium nucleus (1) Alpha is charged (1) Alpha has a mass (1) Gamma penetrates further/ highly (1) Gamma weakly ionising (1) Gamma travels faster (1)

Reverse arguments

em radiation

Gamma has no charge Gamma has no mass examples of penetrating power

alpha highly ionising

ignore vague comments eg stronger Ignore uses and dangers

(2)

Question Number


2(b)(i) D (1)

Question Number


2(b)(ii) B (1)

Question Number


2(c) An explanation linking:

electron(s) (1)

is/are lost/gained (1)

do not allow positive electron

knocked off / removed/ released

(2)


Question Number


QWCQWC * ) An explanation including some of the following points:

Radiation from the front of the lens Alpha particles absorbed by glass Beta particles do not penetrate glass Gamma rays pass through glass Background radiation varies There is a large difference in size between front and back counts Radiation detected is gamma rays only

Radiation from side of the lens Alpha particles cannot penetrate aluminium Beta particles are absorbed by aluminium Gamma rays pass through aluminium There is a small/no difference in size between front and side counts Perhaps a few gamma rays absorbed by aluminium Background radiation varies Likely to contain gamma rays only May be different from front count due to random nature of emissions

Radiation from the back of the lens Alpha particles absorbed by coating and/or glass Beta particles are emitted the from rear surface Gamma rays emitted from radioactive glass There is a large difference in size between front and back counts Background radiation varies Radiation is both beta particles and gamma rays Difference between front and back counts due to beta particles

(6)

Level 0 No rewardable content 1 1 - 2 • a limited explanation mentioning two unrelated points, but without

linking them properly, e.g. beta particles are stopped by thickaluminium, there is most radiation behind the lens


• spelling, punctuation and grammar are used with limited accuracy2 3 - 4 • a simple explanation mentioning some points with an appropriate

linkage to one of the readings e.g. no beta particles escapeforwards because the glass absorbs them OR only gamma raysescape to the side because the aluminium stops alpha and betaparticles


• spelling, punctuation and grammar are used with some accuracy


Total for question 6 = 12 marks

3 5 - 6 • a detailed explanation mentioning some of the points withappropriate linkage to a comparison of at least two of the readingse.g. no beta particles escape forwards because the glass absorbsthem, but beta particles can escape backwards so that count ishigher OR only gamma rays can get through the glass and the thickaluminium, so the front and side counts are about the same




Question Number


3 (a) (i) A alpha particles (1)

Question Number


3 (a) (ii) A suggestion to include

Absorbs (ionising) radiation (from the sources)

Stops/reduces radiation/ radioactivity (reaching people); Stops/reduces (alpha) particles or any named ionising radiation (reaching people); Protects people/keeps it safe;

Ignore – “so the source cannot pass through”

(1)

Question Number


3 (a) (iii) One from Buildings/building materials, food, plants, water, outer space, rocks, air, Sun

Cosmic rays/waves; radon (gas); radioactive waste; nuclear accidents/Chernobyl/nuclear explosions; nuclear power stations;

do NOT accept everywhere

ignore alpha, beta, gamma, microwaves and X-rays, carbon dioxide, nitrogen, (mobile) phones

(1)


Question Number


3 (a) (iv) Any two relevant precautions Distance (between students and source); no touching; no eating; short exposure time;(use of) film badge/ detector ; Protective clothing; Use of lead (lined) box /keep box shut/ sources in box (when not in use); (stand behind/use of) a screen; Do not point (source) at students; Show video/dvd of demo;

Ignore goggles, gloves, lab coats,;

Answers referring to the safety of teacher can score a maximum of one of the 2 marks eg use of tongs

(2)

Question Number


3 (b) (i)

(1)

Calculation of number of half-lives 8 ÷ 4 = 2 (half lives)

evaluation of mass 6 ÷ 2 = 3 ÷ 2 = 1.5 (mg) (1)

Award 1 mark for clearly calculating mass halves after 4 days eg 6/2 = 3 (mg)

6/4 = 1.5 scores 2 marks

Allow rounded 2 mg if clear they calculated 1.5 mg

give full marks for correct numerical answer, 1.5 (mg) even if no working

(2)


Question Number


3 (b) (ii) An explanation linking any two of the following points

• people inhale radon (gas) (1)

• radon is quite likely to/maydecay in the lungs (beforebeing exhaled) (1)

• causes ionisation of cells (inlungs) (1)

• increases risk of (lung) cancer(1)

Breathe in radon (gas)/ breathe it in/ radon (gas) gets into the body;

Gives out radiation in the body / alpha (particles) very ionising;

causes damage to (DNA of) cells (in lung)/cell mutations/kills cells; (Damages the body is insufficient)

(causes lung) cancer

(2)


Question Number


4(a) (i) B (1)

Question Number


4(a) (ii) Any one of the following Rocks Food Radon gas Cosmic rays Own bodies Fall-out Sun/stars

(1)

Plausible named food such as coffee, brazil nut, bananas Space

Specified medical/industrial use of x-rays

Ignore smoke alarms, power stations (in normal use)

(1)

Question Number


4(a) (iii) An explanation linking • personal circumstances such

as geographical location nature of their work lifestyle

(1) • the consequences such as

radiation from radon gas/particular rocks/fall-out (eg Chernobyl) greater exposure to x-rays greater exposure to cosmic rays

(1)

(2)

Question Number


4(a) (iv) D (1)


Question Number


4(b) (i) From the graph Time taken to fall (from 120 to) 60

(1) = 8 days

(1)

Any other suitable pair of readings from graph

8.1, 8.2 Full marks for correct answer even if no working is evident

(2)

Question Number


4(b) (ii) 2.2 (days) (1)

between 2.0 and 2.5 2

(1)

Question Number


4(b) (iii) Any one of the following: • Mutation of dna• Ionisation of cells• (Increases risk of) cancer

(1)

damage / mutate cells (1)


Question number

Answer Mark

5(a)(i) One mark for each correct label (4)

(4)

Question number

Answer Mark

5(a)(ii) B (1)

Question number

Answer Mark

5(a)(iii) zero/0/no charge (1)

Question number

Answer Mark

5(b)(i) 434 (1)

Question number

Answer Additional guidance Mark

5(b)(ii) 34 allow 29 to 39 (1)

Question number


5(b)(iii) Radioactive decay is a random process

allow because background count changes every time

(1)

proton

neutron

electron

nucleus



Level Edexcel

Subject Physics


Topic Radioactivity



38 minutes

/31

/100

Time Allowed:

Score:

Percentage:



Question number


1(a) alpha cannot penetrate casing alpha only travel a few cm in air

(1)

Question number

Answer Mark

1(b) • evidence of division of activity by 2 (1)• 120 (Bq) (1)

(2)

Question number

Answer Mark

1(c) • increase number of starting dice (1)• do more rolls (1)

(2)

Question number

Indicative content Mark


*1(d) Answers will be credited according to candidate's deployment of knowledge and understanding of the material in relation to the qualities and skills outlined in the generic mark scheme.

The indicative content below is not prescriptive and candidates are not required to include all the material which is indicated as relevant. Additional content included in the response must be scientific and relevant.

AO2 (6 marks)

• use a radioactive isotope of iodine as this is taken up bythe gland

• isotope given by injection or orally• gland is in the neck, so cannot use an alpha emitter as

alpha will not exit through the skin• use beta or gamma emitter• isotope has to have a short enough half-life to minimise

exposure to radiation but long enough for the reading tobe taken

• allow time for isotope to reach gland• use Geiger-Müller tube and counter to determine count

rate of isotope in gland• compare with normal count rate to determine whether

uptake of iodine is normal (6)

Level Mark Descriptor

0 No awardable content.

1 1–2 • The explanation attempts to link and apply knowledge andunderstanding of scientific ideas, flawed or simplisticconnections made between elements in the context of thequestion. (AO2)

• Lines of reasoning are unsupported or unclear. (AO2)2 3–4 • The explanation is mostly supported through linkage and

application of knowledge and understanding of scientificideas, some logical connections made between elementsin the context of the question. (AO2)

• Lines of reasoning mostly supported through theapplication of relevant evidence. (AO2)

3 5–6 • The explanation is supported throughout by linkage andapplication of knowledge and understanding of scientificideas, logical connections made between elements in thecontext of the question. (AO2)

• Lines of reasoning are supported by sustained applicationof relevant evidence. (AO2)


Question Number


2(a)(i) B magnetic (1)

Question

Number


2(a)(ii) (high frequency alternating)

voltage

electric field / electrostatic force

electrodes + and – (not just ‘electrodes’) potential difference (p.d.)

(1)

Question

Number


2(a)(iii) A description using the

following:- (charged) particles bombard (1)

atoms/molecules/nuclei / (stable)

elements (1)

(charged) particles {hit / shoot into / fired into / collide with}

generally accept ‘it’ / ‘they’ as alternatives to ‘charged particles’

target (material) / nucleus /

stable isotope

‘neutrons hitting a target’ would get second mark only (neutrons not charged)

2nd mark needs idea of hitting

target nuclei / atoms, not (charged) particles hitting other particles.

(2)

Question Number


2(b)(i) C (1)


Question

Number


2(b)(ii) An explanation linking any three

of the following:-

positron has a positive (charge) (1)

electron has a {negative (charge) / opposite charge(s) }

(1)

these charges cancel out

(1)

gamma rays /waves have no charge (1)

positron has +1 / +e (charge)positron charge is +

electron has -1 / -e (charge) electron charge is –

neutralise / overall charge is zero

Accept for three marks: electron and positron have equal and opposite charges which

cancel out.

(3)

Question

Number


2 (b)(iii) An explanation linking :

positron and electron have

mass(before the annihilation) (1)

(1) gamma (rays produced by annihilation) have energy

(the equation shows) mass (of particles) becomes energy of gamma (rays) (2)

all the mass before the collision becomes the energy of the

gamma (rays) after the particles have been annihilated (2)

E=mc2 reference (1) explained will get the other (1)

(2)



Question Number


3(a)(i) D 27 (1) (1)

Question Number


3(a)(ii) an ex planation linking:

OR

no change in mass(number) (1)

(because) gamma is awave (electromagnetic) /has no mass (itself) (1)

mass decreases (1)

idea of mass – energyequivalence (1) (must beclearly stated)

gamma is only energy / not a particle

nucleus de-excites / rearranged for one mark

do not allow ‘mass number decreases’

(2)

Question Number


3(b) (i) A gamma can penetrate further than

alpha or beta (1) (1)

Question Number


3(b) (ii) description to include: protects / stops radiation

escaping (1)

affectingoperator/doctor/nurse (1)

absorbs (radiation)

other people / others (2)


Question Number


3(b) (iii) two from: non invasive / no surgery

required (1) no radioactive substances

left in the body (1) no anaesthetic used patient does not become

radioactive (1) outpatient procedure (1) does not affect the whole

body (1) (accurate) targeting of

tumour (1) painless (at the time) for

the patient procedure (may be)

quicker

no need to operate / cut open patient / reduces risk of infection

no harmful side effects like chemotherapy

ignore answers\that apply equally to other treatments e.g. ‘kills cancer’

(2)

Question Number


3(b) (iv) explanation linking two from: idea of targeting / beams

concentrate / focus ontumour (1)

avoid damage to healthycells / tissue (1)

(reaching / getting to) allparts of the tumour(1)

more rays hit tumour / beams overlap at tumour ignore ‘(more) beams penetrate more’ / (more) accurate

(2)



Nuclear Fusion & Nuclear Fission

Mark Scheme 1

Level Edexcel

Subject Physics


Topic Radioactivity

Sub Topic Nuclear Fusion & Nuclear Fission


53 minutes

/44

/100

Time Allowed:

Score:

Percentage:



Question

Number


1(a)(i) A nuclear reactor (1)

Question

Number


1(a)(ii) D generator (1)

Question Number


1(b) A description including any four from:

(there are) 89 particles in the nucleus (1)

protons (1)

(there are) 36 (protons) (1)

neutrons (1)

(there are) 53 (neutrons) (1)

i.e. 36 protons and 53 neutronsgains four marks

ignore all references to electrons

(its) {mass/nucleon} number / RAM / Ar / A is 89

{atomic/proton} number /

positive charge / Z = 36

Numbers must be correctly

linked to gain credit e.g. 36 neutrons gets 1 mark (for

neutrons)

53 protons and 36 neutrons gains two marks (for protons and

neutrons)

89 protons and neutrons gets 3 marks

(altogether there are) 89 protons and neutrons. 36 are protons

gains 4 marks

(4)

Question Number


1(c) nucleus (1)

neutron (1)

Answers in this order only (2)


Question

Number


1(d) An explanation linking two of the

following:

control rods absorb neutrons (1)

control rods moved into / inserted

(into reactor core) (1)

to capture more neutrons / increase (surface) area (of control

rods) (1)

(and so) fewer neutrons left ( to cause fission ) (1)

Ignore 'to control/reduce the

reaction(s)’ as paraphrase of stem

accept control rods take in/soak up neutrons

ignore slow down neutrons

accept lowered/pushed down

(into reactor) NOT move(d) up AND down

accept {stops / reduces number (of)} neutrons colliding (with uranium nuclei)

(2)



Question Number


2(ai) B 1 proton only (1) (1)

Question Number


2(aii) Same number of protons (as hydrogen) or

same atomic number( as hydrogen) (1)

Same proton number( as hydrogen) / (they all) have one proton / (their) proton number is 1

accept bottom number is 1/the same

NOT same mass / nucleon number NOT same atomic mass

ignore references to electrons / neutrons

(1)

Question Number


2(b)(i) Helium (nucleus has) positive/+ (charge) (1)

Neutron has no/zero/0 (charge) (1)

helium is +(any number >0 and <5) helium has a larger/bigger charge

neutron is neutral /neutrally charged/uncharged

ignore references to nuclear fusion or masses

(2)


Question Number


2(b)(ii) An explanation linking

(Nuclear fusion/it) occurs in the Sun (1)

(The Sun / Fusion provides) energy/heat/light (needed for life on Earth) (1)

(nuclear fusion/it) is the Sun’s energy source OR (it) occurs in stars

any valid use of fusion in Sun or stars e.g.

without heat (from Sun)Earth would freeze/haveno life

new/heavier elements aremade ( by fusion/ in stars)eg creates helium

(2)

Question Number


QWC *2(c) A description including some of the following points Stages involved in a chain reaction:

o (neutrons released go on to) collide with othernuclei

o causes nuclei to become unstableo (nuclei) split/fission (into daughter nuclei)o releases more neutronso releases energy

Control: -Action of the moderator

o neutrons need to be slowed down/turned intothermal neutrons

o to increase chance of collisiono this is achieved with a moderatoro carbon/graphite/water/heavy water can be used

-Action of control rodso number of neutrons available for collision needs to

be controlledo so that reaction proceeds at a steady rate / does

not increaseo this is achieved by control rods absorbing neutronso boron / silver/indium/cadmium can be used.

Many candidates repeat parts of the question DoNOT give credit for these statements eg neutronsare released during fission

(6)


(Total for Question 6 =12 marks)

LevelLev No rewardable content 1 1 - 2 A limited description which gives one relevant fact

e.g. (neutrons) cause atoms to split.OR (during fission of uranium atom) neutrons collide with atomsOR (nuclear fission) releases energy

OR (3) neutrons are released and two of them are absorbed/taken away



2 3 - 4 A simple description, giving more than one fact, about a chainreaction or control OR at least one fact about both.

e.g. a neutron collides with (uranium) atoms and causes them to split(into daughter nuclei)OR atoms split releasing more neutronsOR an atom splits and releases energyOR (neutrons) cause atoms to split and there are (control) rods tocontrol the neutrons.OR control rods can be lowered into the reactor to absorb neutrons



3 5 - 6 A detailed description involving:- more than two stages of the chain reaction OR a description involving more than one stage of the chain

reaction AND at least one detail about control. OR a description involving more than one detail about control

AND at least one detail about the chain reaction.e.g. Neutrons are slowed down by graphite/water. This makes themmore likely to collide with other nuclei.OR neutrons collide with other nuclei and cause them to split releasingmore neutrons AND these neutrons hit another nuclei causing it tosplitOR neutrons collide with other nuclei and cause them to split releasingmore neutrons AND there are (control) rods to control the neutronsOR neutrons collide with uranium nuclei causing them to split andrelease more neutrons. Control rods of boron absorb some of theneutrons.

the answer communicates ideas clearly and coherently uses arange of scientific terminology accurately. uses nuclei split andnot atoms split.

spelling, punctuation and grammar are used with few errors.


Question Number


3(a) (ii) A suggestion to include

Neutrons do not need to be captured (by another nucleus) / do not play a part in the fusion process

Fusion does not use neutrons

No chain reaction (1)

Question Number


3 (a) (i) All three correct for 2 marks

One or two only correct for 1 mark

Reject any box with more than one line

(2)

Question Number


3 (b) A description to include

Thermal energy used to create steam / boil water(1) (Steam used to drive) turbine (1) (Turbine used to turn) generator (1)

Ignore detail of fission process.

(3)

fuel

Control rod

moderator

Boron

uranium

graphite



Question Number


QWCQWQWC * An explanation including some of the following points

Description of the problem- Nuclei have positive charge- Repel each other- Reduces possibility of suitable collisions- Rate of fusion too small to be useful

Description of how this can be overcomeo Very high temperature ( of fuel)o Very high KE / speed of nucleio High KE can overcome repulsiono Very high density / pressureo Increases possibility of suitable collisions (6)

LevelLev No rewardable content 1 1 - 2 A limited explanation

e.g. The fuel has to be at a high temperature to start the reaction/tomake particles collide.OrThe fuel has to be at a very high temperature and pressure.

the answer communicates ideas using simple language and useslimited scientific terminology


2 3 - 4 A simple explanation.e.g. We need to overcome repulsion of nuclei to make them collide.This is achieved by having a high temperature and pressure.

the answer communicates ideas showing some evidence of clarityand organisation and uses scientific terminology appropriately

spelling, punctuation and grammar are used with some accuracy3 5 - 6 A detailed explanation

e.g. The nuclei repel each other. To overcome this they needvery high kinetic energy which is achieved by generating hightemperature and pressure.




Question Number


4(a)(i) does not emit (ionising) radiation / no (radioactive) decay

it is not radioactive (1)

Question Number


4 (a)(ii) B 5 (1)

Question Number


4 (a)(iii)

A (1)

Question Number


4(b)(i) helium beryllium (1 ) (1)

helium

daughter in right hand boxes

daughter (2)

Question Number


4(b)(ii) a comparison which describes any three of the following:

similarities: • produce (more) neutrons (1)• produce ‘daughter’ (nuclei) (1)

• release energy (1) (1)

• (triggered by) a neutron comingin (1)

• split a (bigger) nucleus

• nucleus becomes unstable(before splitting) (1)

differences: • uranium daughters are different

from each other/ berylliumdaughters are the same (1)

• uranium daughters are heavierthan beryllium daughters (1)

different elements / smaller nuclei for daughters

do not accept split an atom

neutron is absorbed

(3)

8 Be 4


Question Number


4(b)(iii) a description including:

neutron(s) (from first fission) (1) (go on to) cause another fission

(1) collide with another nucleus /atom (2)



Mark Scheme 2

Level Edexcel

Subject Physics


Topic Radioactivity



59 minutes

/49

/100

Time Allowed:

Score:

Percentage:



Question Number


1(a)(i) A electron (1)

Question Number


1(a)(ii) suggestion to include two of

• the ionisation is different(1)

• correct difference inionisation (1)

• the masses are different (1)

• alpha is bigger than beta (1)

• alpha hits more (air)particles (1)

• alpha loses its energy inshorter distance (1)

alpha more ionising (than beta) scores 2 marks

RA (heavier for bigger)

RA

RA

IGNORE references to penetration

(2)

Question Number


1(b) A gamma radiation (1)

Question Number


1(c)(i) A description linking the following:

• neutron decays / changes/ becomes (1)

• (neutron) into proton (1)

• (plus an) electron (1)

quark changes

(quark changes) from down to up / d to u

e- (do not accept β- )

accept n and p for neutron and proton n > p + e- scores 3 marks

IGNORE references to atomic and mass numbers; unstable nuclei; too many neutrons; gamma emitted

(3)


Question Number


1(c)(ii) An explanation linking three of the following:

• mass number doesn’tchange (1)

• (because) same number ofnucleons / quarks (1)

• atomic number goes up byone (1)

• (because) there is an extraproton (1)

emitted electron mass is negligible

proton and neutron have same mass

a neutron has (decayed in)to a proton

(3)


Question Number


2(a) A description including the following points

• steam {drives/turns} turbine (1)

• (which){drives/turns/powers}generator (1)

transfers ke to electrical energy rotates a magnet in coils or coils in magnet accept dynamo for generator

(2)

Question Number


2(b) A description including the following points

• neutron {hits / splits / isabsorbed by} uranium (nucleus)(1)

• producing more neutrons (1)

• at least one neutron can {hit /split / be absorbed by} otheruranium (nuclei) (1)

full marks may be scored on a labelled diagram

fired at other U (nuclei) or “process repeats”

(3)

Question Number


(2(c) krypton-91 (1)

Question Number


2(d) An explanation linking the following points

• removes electrons (1)

• from atoms (1) collides with atoms

ignore references to β decay process (nucleus losing an electron) (2)


Question Number


2(e) An explanation linking the following points

• nuclei are positively charged(1)

• need enough energy toovercome repulsion (1)

ignore references to high temp and pressure

accept same charge accept protons for nuclei accept atoms

and will repel each other

(2)


Question Number


3(a)(i) A 92 (1)

Question Number


3(a)(ii) neutron(s) (1) allow phonetic spelling nutron, newtron, nuetron

(1)

Question Number


3(b) An explanation linking any two of the following points

• a neutron(s)(1)• hits nucleus/nuclei (1)• uranium/nucleus splits (1)

• (producing) neutrons/daughter nuclei/ energy /Kr and Ba (1)

collides/is absorbed breaks/divides

accept chain reaction for 1 mark if no other mark awarded

accept a correctly labelled diagram

(2)

Question Number


3(c) An explanation linking two of the following points

• absorb (1)• neutrons (1)• (influences) chain reaction /

rate of reaction (1)

Accept reverse arguments

collects/removes/takes away

slows down/changes

(2)

Question Number


3(d) An explanation linking any two of the following points

• heats/boils water (1)• to produce steam (1)• to run/turn/spin turbines (1)• to turn/power generators (1)

labelled diagram that indicates process (not just parts). heats boiler

turns a coil in a magnet

(2)

Total marks for question 2 = 8


Question Number


4(a)(i) Neutron(s) Accept phonetic spellings eg newtron(s) or neutron(s) Reject newtons

(1)

Question Number


4(a)(ii) D 9 Be

4

(1)

Question Number


4(a)(iii) A explanation linking the following points

• Charge/electron transfer(1)

• Correct transfer detail(1)

Gains/loses charge Gains an electron = 1mark

Loses (an) electron(s) gains both marks Award 1 mark for gaining a proton as idea of gains charge

(2)

Question Number


4(b) A description including any two of the following points

• Two (light) / (small) nuclei(1)

• Fuse together(1)

• To produce alarge(r)/heaviernucleus/atom /particle(1)

Ignore references to releasing energy as this is in the Q.

two hydrogen (and or helium) nuclei / two protons

join /combine/merge/come / forced together

helium/lithium (nucleus/atom/particle)

(2)


Question Number


QWCQWC * ) A description including some of the following points

• Nucleus absorbs a neutron• Nucleus becomes unstable• nucleus fissions/ splits• (2 or) more neutrons released• daughter products• chain reaction• use of moderator• to control kinetic energy of neutrons/slow down

neutrons• increases chance of further/more (fission) reactions• use of control rods• control rods absorb neutrons• reducing number of neutrons available for fission/to

control (fission) reaction• containment of radioactive materials• little/no radiation enters environmentIgnore references to the release of energy as this is givenin QMarks can be scored by a suitably labelled diagram

(6)

Level

0 No rewardable content

1 1 - 2 • a limited description that contains one or two points and possiblyhas a number of inaccuracies

e.g. Uranium atom splits ......control rods are used (to moderate the reaction) OR Uranium atom absorbs a neutron ....there is a chain reaction OR (In the nuclear reactor) ......chain reaction starts • the answer communicates ideas using simple language and uses


2 3 - 4 • a simple description that links two pointse.g. A uranium nucleus absorbs a neutron and splits.ORA uranium atom splits and releases more neutrons.


• spelling, punctuation and grammar are used with some accuracy


3 5 - 6 • a detailed description that gives a linked statement about fissionplus some detail about control or containment

OR A detailed description that gives two pairs of linked statements about fission e.g Uranium nucleus absorbs a neutron and splits/fissionsAND2 or more neutrons are released and are slowed by a moderator/produce a chain reaction.ORControl rods absorb (some) neutrons to control the reaction.




Question Number


5(a)(i) B (1)

Question Number


5(a) (ii) (equivalent to a) helium nucleus Two protons and two neutrons for 2 marks

helium/mass of 4 for 1 mark

charge of +2 for 1 mark

correct statement of any property for 1 mark

(2)

Question Number


5 (b) A description to include any four of the following

• neutron• is captured by a U-235

nucleus

• nucleus (is) unstable• nucleus splits• into 2 daughter nuclei (of

similar size)• (2 or more) neutrons are

released• energy is released

• collides with /absorbed by(U-235) nucleus

• metastable

• named isotopes

(4)

Question Number


5 (c) An explanation linking • moderator slows down

(absorbs energy from)neutrons

• more likely to be captured/cause fission (if it collideswith a U-235 nuclei)

Reverse argument (2)



Mark Scheme 3

Level Edexcel

Subject Physics


Topic Radioactivity



51 minutes

/42

/100

Time Allowed:

Score:

Percentage:



Question number

Answer Mark

1(a) B (1)

Question number


1(b)(i) The time taken for the activity of a radioactive nuclide to halve (1)

accept for nuclide: isotope sample (1)

Question number


1(b)(ii) Determines number of half-lives and rounds (1) 263/87.7 = 3

Determines that 3 half-lives is 1/2 × 1/2 × 1/2 = 1/8 (1)

Determines mass of Pu-238 after 3 half-lives (1) 925/8 = 115.625 (g)

Determines average energy released per second (1) 115.625 × 0.54 = 62.4 (J)

allow repeated division by 2 allow ecf from step 2 for 1 mark (mass of Pu-238 after1 half-life 925/2 = 462.5 (g))

allow ecf from 1 half-life or from step 3

(4)


Question number

Answer Mark

1(c)(i) An answer that combines the following points of application of knowledge and understanding to provide a logical description:

• proton number/atomic number decreases by 1 (1)• nucleon number/mass number remains unchanged (as p

and n have same mass and mass of electron is(assumed) negligible) (1) (2)

Question number

Answer Mark

1(c)(ii) C (1)


Question number


2(a)(i) An explanation that combines identification – knowledge (1 mark) and reasoning/justification – knowledge (3 marks):

• causes 2 or 3 neutrons tobe released (1)

• (and) one or more ofthese (released) neutronsare absorbed by other (U)nuclei (1)

• which cause furtherfission of U nuclei (1)

• and release furtherneutrons that can beabsorbed, causing a chainreaction (1)

ignore U nucleus ‘splits up’/eq

(4)

Question number

Answer Mark

2(a)(ii) Idea that to get a chain reaction the particle that impacts the nucleus must be the same as the one released (1)

(1)


Question number


2(b) An explanation that combines identification – knowledge (1 mark) and reasoning/justification – knowledge (2 marks):

• reaction will slow down(1)

• because there are fewerfissions (1)

• because fission morelikely with slow neutrons(1)

allow

reactor shuts down/eq

fission requires slow neutrons thermal neutrons for slow neutrons

(3)

Question number

Answer Mark

2(c) An answer that combines the following points of understanding to provide a logical description:

• the reactor is surrounded by a coolant (1)• the thermal energy release from the chain reaction heats

the coolant (1)• the hot coolant is used to generate steam which is used

to drive the turbine (1) (3)


Question Number


3(a) P and M

OR M and P

OR N and Q

OR Q and N

one mark for a pair

(1)

Question Number


3(b) {atomic /proton} number drops by 2 and {mass/nucleon} number by 4 (1)

(which is) alpha decay (1)

2 protons and 2 neutrons are lost 92 90 and 238 234

helium nucleus given off (which is) alpha particle

(2)

Question Number


3(c) same {mass/nucleon} number but {atomic/proton} number increases by 1 (1)

(negative) beta decay (1)

a neutron changes to a proton

ignore GAINS a proton

beta particle /electron given off (2)

Question Number


3(d)(i) alpha Alpha ray, alpha particle, α Ignore capital letters

(1)

Question Number


3(d)(ii) A description including two of

one increases as other increases (1)

rate of increase is in the range from 1.17 to 1.33 (cm/MeV) (1)

range gradually increases more with energy (1)

the particles with higher energy travel further accept values quoted from graph

not (quite) linear/not proportional /curves upwards accept values quoted from graph

(2)


Question Number


3(e) chain reaction needs a neutron from one fission to reach another uranium nucleus/atom (at the right speed) (1)

(fission of 238) needs {fast/high(er) energy} neutrons (1)

idea of continuous nature of chain reaction

the neutrons would be going too slowly /do not have enough energy / lose energy too fast

(2)


Question Number


4(a)(i) Any one from the following

• living things (1)

• space (1)

• nuclear powerstations/accidents (1)

• hospitals (1)

• industrial processes (1)

Ignore radon gas from …

another radioactive rock

a named radioactive substance eg uranium, radium, plutonium

(1)

Question Number


4(a)(ii) statement 2 only (1)

Question Number


4(b) A description of a change including the following points

• used to be thought beneficial(1)

• now known to be extremely{dangerous/hazardous} (1)

{was commonly used (without care)/dangers were not realised}

now known to cause cancer

now can be used safely {under controlled conditions/medical supervision}

(2)

Question Number


4(a)(iii) An explanation linking two of the following points

• radon gas comes from rocks(1)

• types of rocks vary in differentparts of the UK (1)

• where there is more (of this typeof) rock, the reading is higher (1)

may be explained in terms of specific places eg Cornwall

(2)


Question Number


QWC *4(c) A discussion including some of the following points

Appropriate type of radiation is chosen - some passes through- – β and γ not α- significant change with thickness- - β

Half-life - reference to half-life- not too long - too much material needed for activity- not too short – expense of replacing regularly- disposal problems

Safety issues - shielding

• type of radiation• linked to appropriate material and thickness

- security• storage of spares• in use

- safety procedures / precautions in use (6)

Level 0 No rewardable content 1 1 - 2 • a limited discussion of one factor with no reasons e.g.(F)

penetration / half-life/ safety.• the answer communicates ideas using simple language and uses


2 3 - 4 • a discussion linking some of one factor (F) with some reasoning (R)OR two factors e.g. (F) use a source which has a long/short halflife (R) with suitable reason OR (F) use radiation which is affectedby different thicknesses of paper and (F) mention of half-life.


• spelling, punctuation and grammar are used with some accuracy3 5 - 6 • a detailed discussion of at least two factors with some reasons e.g.

(F)F se a (beta) radiation which is affected by thickness (R)because others will not penetrate at all (alpha) or will not be{affected / stopped} by paper (gamma) and (F) some discussion ofhalf-life or safety.




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