GCSE Chemistry Mark scheme Unit 03 - Chemistry June 2016

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GCSE Chemistry Mark scheme Unit 03 - Chemistry June 2016

Transcript Of GCSE Chemistry Mark scheme Unit 03 - Chemistry June 2016

GCSE Chemistry
CH3HP Mark scheme
4402 June 2016
Version/Stage: 1.0 Final

Mark schemes are prepared by the Lead Assessment Writer and considered, together with the relevant questions, by a panel of subject teachers. This mark scheme includes any amendments made at the standardisation events which all associates participate in and is the scheme which was used by them in this examination. The standardisation process ensures that the mark scheme covers the students’ responses to questions and that every associate understands and applies it in the same correct way. As preparation for standardisation each associate analyses a number of students’ scripts. Alternative answers not already covered by the mark scheme are discussed and legislated for. If, after the standardisation process, associates encounter unusual answers which have not been raised they are required to refer these to the Lead Assessment Writer. It must be stressed that a mark scheme is a working document, in many cases further developed and expanded on the basis of students’ reactions to a particular paper. Assumptions about future mark schemes on the basis of one year’s document should be avoided; whilst the guiding principles of assessment remain constant, details will change, depending on the content of a particular examination paper. Further copies of this mark scheme are available from aqa.org.uk
Copyright © 2016 AQA and its licensors. All rights reserved. AQA retains the copyright on all its publications. However, registered schools/colleges for AQA are permitted to copy material from this booklet for their own internal use, with the following important exception: AQA cannot give permission to schools/colleges to photocopy any material that is acknowledged to a third party even for internal use within the centre.

MARK SCHEME – GCSE CHEMISTRY – CH3HP – JUNE 2016
Information to Examiners
1. General The mark scheme for each question shows:
• the marks available for each part of the question • the total marks available for the question • the typical answer or answers which are expected • extra information to help the Examiner make his or her judgement and help to delineate
what is acceptable or not worthy of credit or, in discursive answers, to give an overview of the area in which a mark or marks may be awarded. • the Assessment Objectives and specification content that each question is intended to cover. The extra information is aligned to the appropriate answer in the left-hand part of the mark scheme and should only be applied to that item in the mark scheme. At the beginning of a part of a question a reminder may be given, for example: where consequential marking needs to be considered in a calculation; or the answer may be on the diagram or at a different place on the script. In general the right-hand side of the mark scheme is there to provide those extra details which confuse the main part of the mark scheme yet may be helpful in ensuring that marking is straightforward and consistent.
2. Emboldening and underlining 2.1 In a list of acceptable answers where more than one mark is available ‘any two from’ is
used, with the number of marks emboldened. Each of the following bullet points is a potential mark. 2.2 A bold and is used to indicate that both parts of the answer are required to award the mark. 2.3 Alternative answers acceptable for a mark are indicated by the use of or. Different terms in the mark scheme are shown by a / ; eg allow smooth / free movement. 2.4 Any wording that is underlined is essential for the marking point to be awarded.
3. Marking points 3.1 Marking of lists This applies to questions requiring a set number of responses, but for which students have provided extra responses. The general principle to be followed in such a situation is that ‘right + wrong = wrong’. Each error / contradiction negates each correct response. So, if the number of error / contradictions equals or exceeds the number of marks available for the question, no marks can be awarded. However, responses considered to be neutral (indicated as * in example 1) are not penalised.
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MARK SCHEME – GCSE CHEMISTRY – CH3HP – JUNE 2016

Example 1: What is the pH of an acidic solution?

Student 1 2 3

Response green, 5 red*, 5 red*, 8

Marks awarded 0 1 0

[1 mark]

Example 2: Name two planets in the solar system.

Student 1 2

Response Pluto, Mars, Moon Pluto, Sun, Mars,
Moon

Marks awarded 1 0

[2 marks]

3.2 Use of chemical symbols / formulae
If a student writes a chemical symbol / formula instead of a required chemical name, full credit can be given if the symbol / formula is correct and if, in the context of the question, such action is appropriate.
3.3 Marking procedure for calculations
Full marks can be given for a correct numerical answer, without any working shown.
However, if the answer is incorrect, mark(s) can be gained by correct substitution / working and this is shown in the ‘extra information’ column or by each stage of a longer calculation.
3.4 Interpretation of ‘it’
Answers using the word ‘it’ should be given credit only if it is clear that the ‘it’ refers to the correct subject.
3.5 Errors carried forward
Any error in the answers to a structured question should be penalised once only.
Papers should be constructed in such a way that the number of times errors can be carried forward are kept to a minimum. Allowances for errors carried forward are most likely to be restricted to calculation questions and should be shown by the abbreviation ‘ecf’ in the marking scheme.
3.6 Phonetic spelling
The phonetic spelling of correct scientific terminology should be credited unless there is a possible confusion with another technical term.
3.7 Brackets
(…..) are used to indicate information which is not essential for the mark to be awarded but is included to help the examiner identify the sense of the answer required.
3.8 Accept / allow
Accept is used to indicate an equivalent answer to that given on the left-hand side of the mark scheme. Allow is used to denote lower-level responses that just gain credit.

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MARK SCHEME – GCSE CHEMISTRY – CH3HP – JUNE 2016
3.9 Ignore / Insufficient / Do not allow Ignore or insufficient is used when the information given is irrelevant to the question or not enough to gain a marking point. Any further correct amplification could gain the marking point. Do not allow means that this is a wrong answer which, even if the correct answer is given, will still mean that the mark is not awarded.
4. Quality of Written Communication and levels marking
In Question 2 students are required to produce extended written material in English, and will be assessed on the quality of their written communication as well as the standard of the scientific response.
Students will be required to: • use good English • organise information clearly • use specialist vocabulary where appropriate.
The following general criteria should be used to assign marks to a level.
Level 1: Basic • Knowledge of basic information • Simple understanding • The answer is poorly organised, with almost no specialist terms and their use
demonstrating a general lack of understanding of their meaning, little or no detail • The spelling, punctuation and grammar are very weak.
Level 2: Clear • Knowledge of accurate information • Clear understanding • The answer has some structure and organisation, use of specialist terms has been
attempted but not always accurately, some detail is given • There is reasonable accuracy in spelling, punctuation and grammar, although there may
still be some errors.
Level 3: Detailed • Knowledge of accurate information appropriately contextualised • Detailed understanding, supported by relevant evidence and examples • Answer is coherent and in an organised, logical sequence, containing a wide range of
appropriate or relevant specialist terms used accurately • The answer shows almost faultless spelling, punctuation and grammar.
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MARK SCHEME – GCSE CHEMISTRY – CH3HP – JUNE 2016

Question

Answers

Extra information

1(a)(i)

fizz / effervescence / bubbles
because carbon dioxide produced / released limewater turns cloudy / milky / white because (a precipitate of or solid) calcium carbonate forms

allow calcium carbonate decreases in size or dissolves allow because gas produced / released
allow because of carbon dioxide if not already credited

Mark AO / SpecRef
1 AO2/AO3 3.4.1d, 3.6.2b
1
1
1

1(a)(ii)

allow –OH

1

AO1

do not allow lower case ‘h’

3.6.2a

1(a)(iii) acid ester(s)

must be in this order

1

ignore any name of an acid

1

1(b)

all four correct 2 marks

any two correct 1 mark

white (precipitate) no change

2

no change

no change

1(c)(i) lilac red

must be in this order

allow purple

1

1

1(c)(ii) colours are masked / changed

1

by each flame colour

Total

12

AO1 3.6.2b
AO2 3.4.1e,f
AO1 3.4.1a
AO3 3.4.1a

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Question

Answers

Extra information

Mark

2

6

Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response. Examiners should also refer to the information on page 5 and apply a ‘best-fit’ approach to the marking.

0 marks

Level 1 (1–2 marks) Level 2 (3–4 marks) Level 3 (5–6 marks)

No relevant content.

There is a simple description of using some of the apparatus.

There is a description of an experimental method including addition of acid to alkali which may include an indicator or colour change and may include a measurement of volume.

There is a description of titrations that would allow a comparison to be made between the two solutions of hydrochloric acid.

examples of chemistry points made in the response could include:
• acid in burette or flask • alkali/sodium hydroxide or acid in burette or flask • volume of acid or alkali measured using the pipette • indicator in flask • white tile under the flask • slow addition • swirling/mixing • colour change of indicator • burette volume measured

AO / SpecRef
2AO1 / 3AO2 / 1AO3 3.4.1g

Total

6

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Question

Answers

3(a)(i) atomic weights

Extra information allow atomic masses

Mark AO / SpecRef

1

AO1

3.1.1a

3(a)(ii) proton

allow proton number

3(b)(i) F/fluorine

allow F2

3(b)(ii)

any one from: • copper has a higher density • copper is stronger • copper is harder • copper is less reactive

allow converse for potassium
allow named property
ignore colour, conductivity, melting point and boiling point

3(b)(iii) relative distance from nucleus relative attraction to nucleus

max 3 marks if ‘outer’ not mentioned
allow more / fewer energy levels / shells or larger / smaller atom
allow more / less shielding

1

AO1

3.1.2a

1

AO3

3.1.3a,b,f

AO1 3.1.3c

1

2AO1 / 1AO2 / 1AO3 1 3.1.3b,f,h
1

relative ease of gain or loss of

1

electron

1 opposite explanation of ease of gain or loss of electron for other group

Total

8

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Question

Answers

Extra information

4(a) development / maintenance of allow lowers risk of heart

teeth / bones

disease

because contains calcium ions / compounds

allow contains calcium

4(b) scum or calcium stearate

4(c) 4(d) Total

temporary hard water contains calcium hydrogencarbonate or hydrogencarbonate ions
when heated / boiled these decompose
to produce a precipitate / scale or to produce calcium carbonate
coats the heating element or coats the kettle

allow hydrogencarbonate
allow decompose (in the kettle)
allow prevents heat / energy transfer to the water

ions must be mentioned once to gain both of the first two marking points

ion exchange resins contain sodium / hydrogen ions

which replace / remove the calcium / magnesium ions
so removing the hardness or producing soft water

allow displace, but do not allow references to reactivity series

Mark AO / SpecRef

1

AO1

3.2.1f

1

1

AO1

3.2.1a

1

1AO1 /

2AO2 /

1AO3

1 3.2.1c,d,e

1

1

2AO1 / 1AO2 3.2.1g, 3.2.2b 1
1
1
10

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Question

Answers

Extra information

Mark AO / SpecRef

5(a)

CH4 + 2O2 

CO2 + 2H2O

allow multiples

1

AO2

3.3.1a

5(b) 3444 J

3 if answer incorrect:
one mark for temperature increase = 16.4 °C
one mark for mass of water = 50 g
ecf for one incorrect value gains two marks for correct calculation
no ecf for two incorrect values

5(c)(i) 1276 (kJ per mole)

ignore + or -

3

if answer incorrect:

[(5 x 413) + 347 + 358 +467] + [(3 x 495)] = 4722 (1 mark)

[(4 x 799) + (6 x 467)] = 5998 (1 mark)

correct subtraction of calculated energy values (1 mark)

5(c)(ii) because energy released

allow converse

2

when bonds form is greater

than energy used when bonds

broken

if no mark awarded allow

one mark for energy is used

to break bonds

or

one mark for energy is released when bonds form

AO2 3.3.1a
AO2 3.3.1f
AO1 3.3.1e,f

5(c)(iii)

products line lower than reactants
activation energy labelled
overall energy change labelled

1 2AO2 /

1AO3

1

3.3.1d

1

Total

12

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