Mark Scheme (Results)

Summer 2023

Pearson Edexcel GCSE

In Chemistry (1CH0)
Paper 2H
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Summer 2023
Publications Code 1CH0_2H_2306_MS
All the material in this publication is copyright
© Pearson Education Ltd 2023
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.
• 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.
Mark schemes have been developed so that the rubrics of each mark scheme reflects the characteristics
of the skills within the AO being targeted and the requirements of the command word. So for example
the command word ‘Explain’ requires an identification of a point and then reasoning/justification of the
point.
Explain questions can be asked across all AOs. The distinction comes whether the identification is via a
judgment made to reach a conclusion, or, making a point through application of knowledge to
reason/justify the point made through application of understanding. It is the combination and linkage
of the marking points that is needed to gain full marks.
When marking questions with a ‘describe’ or ‘explain’ command word, the detailed marking guidance
below should be consulted to ensure consistency of marking.

Assessment Command Word

Objective

Strand Element Describe Explain

AO1 An answer that combines the marking An explanation that links

points to provide a logical description identification of a point with
reasoning/justification(s) as required

AO2 An answer that combines the marking An explanation that links

points to provide a logical description, identification of a point (by applying
showing application of knowledge and knowledge) with
understanding reasoning/justification (application of
understanding)

AO3 1a and An answer that combines points of

1b interpretation/evaluation to provide a
logical description

AO3 2a and An explanation that combines

2b identification via a judgment to reach
a conclusion via
justification/reasoning

AO3 3a An answer that combines the marking

points to provide a logical description
of the plan/method/experiment

AO3 3b An explanation that combines

identifying an improvement of the
experimental procedure with a linked
justification/reasoning
 2306 1CH0_2H
Paper 2H

Question Answer Additional guidance Mark

number
1(a) an answer of 0.036 / 0.04 with or without working (2)
scores 2 marks AO2-1

134.67 - 133.59 = 1.08 (1) 1.08 with no working scores 1 mark

(1.08) = 0.036 (1) allow ECF for MP2 if all 3 pieces of data have been
30 used in MP1

Question Answer Mark

number
1(b) any two from : (2)
AO1-2
• distance from beaker to {flame/wick/burner} (1)

• size of wick (1) allow type of wick

• volume of water (1) allow amount or mass for volume

• temperature increase of water (1) allow initial temperature of water

• {size/shape/type} of beaker (1)

ignore time
ignore same person
ignore volume/mass of fuel
Question Answer Mark
number
1(c) any two from : (2)
AO3-3
• move beaker closer to spirit burner (1)

• use a metal {calorimeter/beaker} instead of glass (1)

• use (draft) shields (1)

• place a lid on the beaker (1)

• insulate the (sides of the) beaker (1) reject use a polystyrene beaker
Question Answer Additional guidance Mark
number
2(a) (3)
6 or 7 points plotted correctly (2) allow +/- half a square AO2-1
or
4 or 5 points plotted correctly (1)

best fit curve starting at (0,0) (1) for MP3, curve must be a single smooth curved line going through
most or all of THEIR plotted points (ecf allowed), or
if the points are not visible, through most or all of the correct values

reject curves going above or below 100cm3 by more than half a

square

reject straight line / dot to dot straight lines

bar charts – max 2 marks for plotting points if time value is clear

Question Answer Additional guidance Mark

number
2(b)(i) 13 answer may be given in table (1)
AO2-1
Question Answer Additional guidance Mark
number
2(b)(ii) An explanation linking Note: a comparison of the rate of marble chips with (3)
that of marble powder is ignored AO3-2
ignore anything about rate increasing at the
beginning / starts fast

• rate of reaction decreases / reaction is slower (1) allow (rate of) reaction slows down
ignore references to volumes of gas produced
ignore reaction stops

• as {reactants /acid/ marble chips} are used up (1) allow {concentration/amount} of acid decreases /
marble chips getting smaller
allow {marble chips have / acid has} reacted
allow less {reactants/ marble chips/ acid} available
ignore limiting factor/ reaction is ending

• so less frequent collisions (1) allow fewer (successful) collisions

ignore less particles have less energy
Question Answer Additional guidance Mark
number
2(c) graph to show there must be a line from part (a) to award these marks (2)
if lines are not labelled, make a reasonable assumption AO3-2
about which is C

mark independently.

• initial line steeper and to the left (1) line should start from start of original line

• line levelling off at 100 cm3 before 5 minutes (1) all levelling off within half a square of original line
Question Answer Additional guidance Mark
number
3(a) An explanation linking (2)
AO1-1
• 1 electron (1) allow 1 is the last number of the electronic configuration (1)
ignore electronic configurations written out
reject incorrect number of electrons

• in outer shell(s) (1) MP2 depends on MP1

for outer allow {highest energy / last}
for shell allow ring, energy level, orbital

allow:
1 outer electron (2)
1 valence electron (2)
have to lose 1 electron to get full outer shell (2)
same number of electrons in outer shell (1)
forms a +1 ion by losing one electron (1)

Question Answer Mark

number
3(b) C soft enough to be cut by a knife / low melting point is the only correct answer (1)
AO1-1
A and D are incorrect because alkali metals do not have a high density
B is incorrect because alkali metal compounds are not blue in colour

Question Answer Additional guidance Mark

number
3(c) 2 K( s ) + Br2(g) → 2 KBr(s) allow multiples (2)
AO2-1
balancing (1) ignore ‘two’
state symbol s (1) ignore ‘solid’
Question Answer Additional guidance Mark
number
3(d)(i) An explanation linking reject compound/ molecule/ ion / elements once (2)
AO1-1
• (atoms) {of same element / with same number of allow same protons
protons} / all contain 19 protons / same atomic ignore electrons
number (1) reject different protons

• different number of neutrons / different mass number allow different / extra / more / fewer neutrons
/ have 20, 21, 22 neutrons (1) ignore different mass / relative atomic mass
reject different electrons

Question Answer Additional guidance Mark

number
3(d)(ii) 39.1348/39.135/ 39.13/ 39.1 with or without Final answer of 39 with no working scores 0. (2)
working scores 2 Final answer of 39 rounded from correct working AO2-1
scores 2.
allow rounding of values in the 3 sums
allow ecf for MP2 if transcription error(s) e.g 93.52
allow ecf for MP2 if formula is correct but error in
93.25 x 39 + 40 x 0.02 + 6.73 x 41 = 3913.48 (1) calculation

3913.48 = 39.1348 (1)

100

OR

39 x 93.25 and 0.02 x 40 and 6.73 x 41 (1)

100 100 100

36.3675 + 0.008 + 2.7593 = 39.1348 (1)

Question Answer Additional guidance Mark
number
4(a) proton allow (2)
atom AO1-1
molecule proton
nanoparticle in the correct order (2) molecule
atom
nanoparticle (1)

Question Answer Mark

number
4(b)(i) C 9.0 x 10-8 is the only correct answer (1)
AO2-1
A is incorrect as it is 90000 nanometres
B is incorrect as it is 9000 nanometres
D is incorrect as it is 0.09 nanometres
Question Answer Additional guidance Mark
number
4(b)(ii) 1:15 with or without working 3 marks allow ecf (3)
AO3-2

surface area = 90 x 90 x 6 = 48 600 (1)

volume = 90 x 90 x 90 = 729 000 (1)

729 000 = 15 (1) surface area calculated correctly evaluated (1)

48 600 volume calculated
answer = 1 : 15
ratio 1:90 scores 2

48600 = 0.066 (2)

729000

729000 = 90 (2)
8100

8100 = 0.011 (1)

729000
Question Answer Additional guidance Mark
number
4(c)(i) allow lowercase f (2)
allow diagram to show 1, 2, 4 or 6 carbon atoms eg AO2-1

(2)

OR
2 marks
repeat unit including:
• no double bond (1) ignore brackets around repeat unit and n
• rest of repeat unit with linking bonds (1)
Question Answer Additional guidance Mark
number
4(c)(ii) Use (1) USES (3)
Property (1) allow: pans / saucepans / tennis rackets / named AO1-1
Reason (1) kitchen equipment / piping / skis
(Property & reason MUST depend on use)
ignore: sports equipment (in general) / ‘kitchenware’
Examples: / windows / window ledge / toothpaste

• for coating (frying) pans (1) PROPERTIES

• because it is {slippery/non stick} (1) allow: slippery / smooth / non-stick / unreactive /
• food will not stick to the (frying) pan (1) does not conduct electricity / non-toxic / high
melting point
OR
ignore: strong / lightweight / high boiling point
• clothing /carpets (1)
• because it is non-stick (1) other reasonable uses include:
• easy to clean / will not stain (1)
lubricants - reduces friction
OR graft material in surgery – inert/non-reactive
prevent insects from climbing surfaces - slippery
• bottom of skis (1) insulation of wiring & electrical circuits – does not
• because it is slippery (1) conduct electricity/high melting point
• less friction on snow (1) plumbers’ tape – flexible/waterproof
bottles – inert/non-reactive
raincoat / rainjacket – waterproof
GoretexTM clothing - waterproof
Umbrella – water repellant
flame retardant material (2) – high melting point
hair straighteners – non-stick/no hair damage

allow any reasonable use

Question Answer Mark
number
5(a) B carbon dioxide is the only correct answer (1)
AO3-2b
A, C and D are incorrect because the gas thought to be the highest percentage in the Earth’s early
atmosphere is carbon dioxide

Question Answer Additional guidance Mark

number
5(b) for any marks must be molecule with two H and (2)
one S atom, but ignore shape/ bond angles AO2-1
unlabelled atoms can be assumed to be H and S
max 1 mark if charge on molecule

allow dots or crosses or a mixture of both

(2) allow with no circles

OR ignore inner shells even if incorrect

one shared pair of electrons between S atom and each

of two H atoms (1)

rest of molecule correct (1) MP2 dependent on MP1

Question Answer Additional guidance Mark
number
5(c) An explanation linking any 3 from: ignore any references to nitrogen oxides/ nitric (3)
acid AO1-1
• sulfur/ S (is present as an impurity) (1)

• (when fuel burns) {impurity/sulfur} is S + O2 → SO2 scores MP1, MP2 and MP3
{burned/ combusted/ oxidised/ reacts with
oxygen} (1)

• sulfur dioxide/ SO2 (formed) (1)

• sulfur dioxide dissolves in {rain/ water/ allow sulfur dioxide reacts with {rain/ water/
clouds} (1) clouds}
ignore sulfur dioxide mixes with {rain/ water/
clouds}

• sulfuric acid is formed (1) allow forms sulfurous acid.

suitable equation forming H2SO3 or H2SO4 scores
MP3, MP4 and MP5

Question Answer Additional guidance Mark

number
5(d)(i) pH meter allow pH probe (1)
allow universal indicator/ UI AO3-3a

reject any other indicators

ignore pH paper/ pH strips/ pH scale/ pH indicator

Question Answer Additional guidance Mark
number
5(d)(ii) An explanation linking one pair from : (2)
AO3-3b
• use {sulfuric / sulfurous} acid (rather than allow formulae
hydrochloric acid) (1)

• because acid rain contains {sulfuric / sulfurous}

acid / does not contain hydrochloric acid (1)

OR

• use rainwater rather than pure water (1)

• because rainwater {does not have a pH 7 of / is

not pure water} (1)

OR

• use acid with a higher pH / a pH between pH 4 allow use a less concentrated acid
and pH 6 (1)
allow use a range of pH values (1)
• because acid rain has a higher pH than 2 (1) so that the effect of different pH can be found (1)

allow a specific control variable

e.g: kept at same light levels (1)
because the plants may grow faster in different
light conditions (1)

ignore:
use more plants/ use a variety of plants / leave for
a longer time / have several sets of the experiment
/ repeat the experiment / water every day
Question Answer Mark
number
6(a)(i) C oxidising, harmful and hazardous to the environment is the only correct answer (1)
AO1-1
A, B are incorrect because none of the substances are flammable

D is incorrect because the third symbol does not mean corrosive

Question Answer Additional guidance Mark

number
6(a)(ii) An explanation linking one pair from: mark independently (2)
ignore any other suggestions not included in AO2-2
markscheme

• use a fume cupboard (1) ignore masks/ breathing apparatus/ well

ventilated room
• because (chlorine/it) is a toxic gas (1) allow poisonous

OR

• wear gloves/ goggles/ safety glasses (1)

• because the concentrated hydrochloric acid is allow acids ‘burns’ skin/ eyes
corrosive (1)

OR
• do not dispose of any reactants / products down allow dispose of substances correctly
the drain (1)

• because {potassium manganate/ chlorine /it} allow specific hazards e.g. kills fish
is hazardous to the environment (1)
Question Answer Additional guidance Mark
number
6(b) so {gas / chlorine} moves (from flask) to gas jar ignore to deliver substances (1)
ignore to connect the apparatus / to stop gas AO1-1
escaping

Question Answer Additional guidance Mark

number
6(c) An explanation linking: reject chloride once (2)
AO2-2
• chlorine will turn the damp litmus paper (red reject bleaches then turns red for MP1
then) white / bleached (1)

• so that you can see when the jar is full (1) allow so you know {when to stop the reaction/
when enough chlorine has been made}/ to detect
chlorine / to show that chlorine has been made / to
see if chlorine is escaping

allow gas for chlorine in MP2

reject to test pH for MP2

Question Answer Additional guidance Mark
number
allow multiples (3)
6(d) 2KMnO4 + 16HCl → 2MnCl2 + 2KCl + 5Cl2 + 8H2O do not penalise incorrect cases, subscripts e.g allow AO2-1
CL2
ignore state symbols

all 6 formulae on correct sides of arrow (2)

4 or 5 formulae on correct sides of arrow (1)
balancing of correct formulae only (1)

Question Answer Additional guidance Mark

number
7(a)(i) ignore any circles drawn on other molecules (1)
must not include hydrogen AO1-1
Question Answer Additional guidance Mark
number
7(a)(ii) allow CH2BrCHBrCH3 (1) (2)
AO2-1
OR

Br on neighbouring carbon atoms (1)

rest of molecule correct with no double bond, two

bromines and no extra products (1) (1)

OR

(1)
ignore the molecular formula
Question Answer Additional guidance Mark
number
7(a)(iii) water (1) allow H2O (2)
AO2-1
carbon dioxide (1) allow CO2

allow answers in either order

allow lowercase/non subscripts
Question Indicative content Mark
number
*7(b) Answers will be credited according to candidate's deployment of knowledge and understanding of the (6)
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
that is indicated as relevant. Additional content included in the response must be scientific and relevant.

AO1 6 marks
FERMENTATION
• dissolve glucose in water to form a solution
• place glucose solution in a suitable flask
• add yeast to glucose solution
• place fermentation mixture in warm room/water bath / 25-40C
• fit air lock or equivalent in neck of flask
• reaction stops when bubbles stop
• decant ethanol solution from yeast/ethanol mixture or filter out yeast
CONCENTRATION
• fractional distillation
• place the dilute ethanol in round bottom flask /suitable vessel
• add a fractionating column onto the round bottom flask /suitable vessel
• and a thermometer on top of the of fractionating column
• add condenser to top of fractionating column
• run water into bottom of condenser
• heat round bottom flask/vessel
• to above boiling point of ethanol / below the boiling point of wate
• collect concentrated ethanol from end of condenser

Allow labelled diagrams

Level Mark Descriptor
0 No rewardable material.
Level 1 1–2 add yeast to glucose (1)
a basic description of concentrate the ethanol using fractional distillation (1)
either process add yeast to glucose then use fractional distillation (2)
or a very basic use fractional distillation, heat the ethanol solution to above boiling point of ethanol (2)
description of both
Level 2 3–4 add yeast to glucose solution and keep in at 25-35C then use fractional distillation to
A detailed description concentrate (3)
of one of the processes mix glucose in water to form a solution and add yeast and keep warm, cotton wool in neck of
or a basic description flask, decant yeast when bubbles stop (4)
of both processes Use fractional distillation, place the dilute ethanol in round bottom flask, add a fractionating
column with a thermometer add condenser to top of fractionating column. Heat the round
bottom flask to above boiling point of ethanol (4)
Level 3 5–6 put glucose and yeast into conical flask and warm to 35C, use an airlock to prevent oxygen,
both processes decant ethanol solution from mixture then use fractional distillation (5)
described with one put glucose solution and yeast into conical flask and warm to around 30oC, use an airlock to
described in detail prevent oxygen entering flask, decant ethanol solution from mixture then use fractional
distillation, place the dilute ethanol in round bottom flask, add a fractionating column onto the
round bottom flask and heat, collect concentrated ethanol from top of fractionating column (6)
Level Mark Descriptor

0 • No rewardable material.
Level 1 1-2 • Demonstrates elements of chemical understanding, some of which is inaccurate. Understanding of
scientific, enquiry, techniques and procedures lacks detail. (AO1)
• Presents a description which is not logically ordered and with significant gaps. (AO1)
Level 2 3-4 • Demonstrates chemical understanding, which is mostly relevant but may include some inaccuracies.
Understanding of scientific ideas, enquiry, techniques and procedures is not fully detailed and/or
developed. (AO1)
• Presents a description of the procedure that has a structure which is mostly clear, coherent and logical
with minor steps missing. (AO1)
Level 3 5-6 • Demonstrates accurate and relevant chemical understanding throughout. Understanding of the
scientific ideas, enquiry, techniques and procedures is detailed and fully developed. (AO1)
• Presents a description that has a well-developed structure which is clear, coherent and logical. (AO1)
Question Answer Mark
number
8 (a) D 82% is the only correct answer (1)
AO2-1
A is not correct as this is percentage of hydrogen in ammonia
B is not correct as this is the mass of hydrogen multiplied by the mass of nitrogen
C is not correct as this is the mass of hydrogen multiplied by the mass of ammonia

Question Answer Mark

number
8 (b)(i) C arrow R is the only correct answer (1)
AO2-1
A, B and D are incorrect because they do not show the activation energy
Question Answer Additional guidance Mark
number
8 (b)(ii) A description to include: (2)
any two for 1 mark AO1-1
all three for 2 marks

• energy is taken in breaking bonds (in the allow breaking bonds is endothermic
reactants)

• energy is given out making bonds (in the allow forming bonds is exothermic
products)

• more energy is given out than taken in allow less energy taken in than given out

ignore products have less energy than reactants

ignore reaction is exothermic / gives out energy alone

for energy taken in allow : absorbed / needed / used

/required

for energy given out allow: released

Question Answer Additional guidance Mark
number
8 (b)(iii) -76 with or without working scores 4 allow ecf (4)
AO2-1
BROKEN
944 + (3 x 436) = 2252 (1) ignore sign

MADE
2 x (3x388) = 2328 (1) ignore sign

DIFFERENCE
(broken) 2252 – (made) 2328 (1) MP3 for difference between their 2 values

ANSWER
= - 76 (1) MP4 for correct evaluation, including correct sign,
of bonds broken – bonds made using their values

(+)76 scores 3
(+)1088 scores 3
(+)604 scores 3
(+)1476 scores 3
-1088 scores 2
-604 scores 2
Question Answer Additional guidance Mark
number
8 (c) an explanation linking Mark independently (3)
AO1-1
AMMONIA
ammonia {is simple molecular / has weak allow weak {forces / bonds} between molecules
intermolecular forces} allow intermolecular bonds
reject anything ionic for MP1

SILICON DIOXIDE
silicon dioxide is {giant covalent / has strong allow macromolecular
covalent bonds} (1) reject anything ionic / simple molecular for MP2

DIFFERENCE
more {heat / energy} to break bonds in silicon in MP3 mark is for saying more energy/ heat needed
dioxide than intermolecular forces in ammonia to break the ‘attractions’ in silicon dioxide than in
ammonia. The ‘attractions’ do not have to be correct.

allow the energy required to break the attractions in

ammonia is small and the energy required to break
the attractions in silicon dioxide is large
Question Answer Mark
number
9(a)(i) C surfacing roads fuel for trains fuel for large ships is the only correct answer (1)
AO1-1
A and B are incorrect as bitumen is not used as a fuel for large ships

D is not correct as diesel oil is not used for fuel for large ships

Question Answer Additional guidance Mark

number
9(a)(ii) An explanation linking allow ORA (2)
AO1-1
• (viscosity increases down the column) as
molecules are {larger/ longer/ more carbons} (1)

• because there are stronger {intermolecular allow stronger intermolecular bonds/ forces of
forces / forces between molecules} (1) attraction/ (surface area of) contact

allow more intermolecular forces

Question Answer Additional guidance Mark
number
9(b) allow ecf throughout (4)
Mr of CH2 = 12 + (2x1) = 14 (1) MP1 must be for CH2 AO3-1

56 = 4 (1) allow 14 x 4 = 56
14

formula of Y = 4 x CH2 = C4H8 (1) allow Y has 4C and 8H

C4H8 without working scores MP3 only.
C4H8 = (4 x 12) + (8 x 1) = 56 scores MP1, 2 and 3

formula of X = (C6H14 + C4H8 =) C10H22 (1) for MP4 must be written as formula
C10H22 without working scores MP4 only

ecf can be awarded for MP4 as long as working for

alkene to be added is seen

ignore formula of X = (C6H14 + CH2 =) C7H16

Question Indicative content Mark
number
9(c) Answers will be credited according to candidate's deployment of knowledge and understanding of the material (6)
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 that
is indicated as relevant. Additional content included in the response must be scientific and relevant.

AO1 (3 marks) and AO2 (3 marks)

Ignore any issues with methane itself e.g. it is a greenhouse gas.
Ignore different colours of flame with open/ closed air hole.

OPEN AIR-HOLE
• air-hole open, allows lots of oxygen to mix with methane
• therefore complete combustion takes place
• CH4 + 2O2 → 2H2O + CO2
• carbon dioxide and water are produced.

CLOSED AIR-HOLE
• air-hole closed, less oxygen can enter to mix with methane
• therefore incomplete combustion takes place
• e.g 2CH4 + 3O2 → 2CO + 4H2O (allow other correct examples)
• carbon monoxide can be produce

HARMFUL EFFECTS
• CO is odourless and colourless
• carbon monoxide combines with haemoglobin in place of oxygen/ reduces capacity of blood for oxygen
• therefore toxic
• carbon/ soot can also be produced
• can aggravate asthma / respiratory problems
• soot makes buildings dirty
• carbon dioxide and water are greenhouse gases
• absorb heat energy radiated from Earth which is re-radiated back into the atmosphere
• increases greenhouse effect
• causes global warming/ climate change
• melt polar ice caps / sea levels rise
Level Mark Descriptor
0 No rewardable material.
Level 1 1–2 closed air-hole gives less oxygen (1)
A description of open or closed air -hole or closed air-hole gives less oxygen, open air-hole gives more oxygen (1)
description of one harmful effect closed air-hole gives incomplete combustion (1)
closed air-hole has less oxygen so incomplete combustion (2)
complete combustion gives carbon dioxide (1)
when the air-hole is open, oxygen allows complete combustion gives carbon
dioxide and water (2)

Level 2 3–4 A closed air-hole gives less oxygen which produces soot and carbon monoxide
Description of two of: open air-hole/ which is toxic because it bonds to haemoglobin. (3)
closed air hole/ harmful effect
More oxygen gives carbon dioxide and water and incomplete combustion gives
carbon monoxide and water. (4)

Complete combustion produces carbon dioxide and water which are both
greenhouse gases. Greenhouse gases absorb heat energy radiated from the
earth and re-radiates it, this causes global temperatures to rise and leads to an
increase in polar ice caps melting. (4)

Level 3 5–6 Incomplete combustion makes carbon monoxide but complete combustion
All three aspects must be covered produces carbon dioxide and water which are both greenhouse gases.
Description of all three of: open air-hole/ Greenhouse gases absorb heat energy radiated from the earth and re-radiates
closed air-hole/ harmful effect(s) it, this causes global temperatures to rise and leads to an increase in polar ice
caps melting. (5)

A closed air-hole gives incomplete combustion which produces carbon monoxide

which is an odourless and colourless toxic gas. Complete combustion produces
carbon dioxide and water which are both greenhouse gases. Greenhouse gases
absorb heat energy radiated from the earth and re-radiates it, increases the
greenhouse effect and temperature of the Earth’s atmosphere. (6)
Level Mark Descriptor

0 • No awardable content
Level 1 1-2 • Demonstrates elements of chemical understanding, some of which is inaccurate. Understanding of
scientific ideas lacks detail. (AO1)
• The explanation attempts to link and apply knowledge and understanding of scientific ideas, flawed
or simplistic connections made between elements in the context of the question. (AO2)

Level 2 3-4 • Demonstrates chemical understanding, which is mostly relevant but may include some inaccuracies.
Understanding of scientific ideas is not fully detailed and/or developed. (AO1)
• The explanation is mostly supported through linkage and application of knowledge and understanding
of scientific ideas, some logical connections made between elements in the context of the question.
(AO2)

Level 3 5-6 • Demonstrates accurate and relevant chemical understanding throughout. Understanding of the
scientific ideas is detailed and fully developed. (AO1)
• The explanation is supported throughout by linkage and application of knowledge and understanding
of scientific ideas, logical connections made between elements in the context of the question. (AO2)
Question Answer Additional guidance Mark
number
10 (a)(i) An explanation linking one pair from: (2)
AO3-3b
• use a (nichrome) wire instead of a wooden splint (1) allow metal loop / metal rod / platinum loop /
(metal) inoculating loop
• so the wood does not burn / as the wire will not
interfere with the flame colour (1)

OR

• leave the wooden splint to soak in water longer (1)

• so that the wooden splint does not burn when

testing the sample (1)

allow use hydrochloric acid (instead of water) (1)

so that the sample vaporises more easily (1)

ignore (use hydrochloric acid) to remove

impurities / sterilise

ignore use a photometer

Question Answer Mark
number
10 (a)(ii) B lilac is the only correct answer (1)
AO1-1
A is incorrect as this is the colour for copper
C is incorrect as this is the colour for calcium
D is incorrect as this is the colour for lithium

Question Answer Additional guidance Mark

number
10 (b) A description including : (3)
AO1-1
• add (dilute) nitric acid (1) ignore warming
reject hydrochloric acid /sulfuric acid for MP1

• add silver nitrate (solution) (1)

• a white precipitate (1) MP3 is dependent on addition of silver nitrate

Question Answer Additional guidance Mark
number
10 (c)(i) 2.1 scores 3 with or without working allow ECF throughout (3)
AO2-1

25 = 0.025 (1)
1000

0.025 x 83 = 2.075 (1)

= 2.1 (1)

Question Answer Additional guidance Mark

number
10 (c)(ii) Ba2+ + SO42-→ BaSO4 (3) allow 3Ba2+ + 3SO42- → 3BaSO4 (3)
incorrect balancing of correct species max 2 AO2-1

Ba2+ (1) reject Cl-

SO42- (1) reject Al3+

→ BaSO4 (1) reject AlCl3

ignore any state symbols even if incorrect