AQA CERTIFICATE Science: Double Award

Transcription

1 AQA CERTIFICATE Science: Double Award 8404/C/F Mark scheme 8404 June 205 Version:.0 Final

2 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 205 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.

3 . General Information to Examiners 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 2. 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. 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 ) are not penalised. Example : What is the ph of an acidic solution? ( mark) Student Response Marks awarded green, red*, 5 3 red*, of

4 Example 2: Name two planets in the solar system. (2 marks) Student Response Marks awarded Neptune, Mars, Moon 2 Neptune, Sun, Mars, Moon 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 is 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 e.c.f. 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 Ignore / Insufficient / Do not allow Ignore of insufficient is used when the information given is irrelevant to the question or not enough to gain the 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 of

5 (a) + 0 allow + AO.2d (b)(i) neutrons AO.2h (b)(ii) electrons AO 2.b, 2.g (b)(iii) molecules AO 2.g, 2.h (c)(i) 8 AO2.2f,.2i (c)(ii) 8 must be: AO2 0 8 (electrons and) 0 (neutrons).2e,.2f,.2i Total 8 5 of

6 2(a)(i) B AO 5.4a 2(a)(ii) Good conductor of electricity AO 5.4a 2(b)(i) Coke AO 5.2b 2(b)(ii) 4% carbon AO 5.4b 2(b)(iii) Steel AO 5.4c 2(b)(iv) Dental braces AO Total 6 5.3g 6 of

7 3(a)(i) C 6 H 4 ignore size of numbers AO2 7.2b 3(a)(ii) Only single bonds AO2 7.2a 3(b)(i) 2n ignore size do not allow N AO2 8.b 3(b)(ii) AO2 8.b 3(c) (vapours) cool (as they rise) allow hot at bottom / cool at top / temperature gradient ignore heat it = vapours AO 7.c condense (into fractions) at different boiling points / temperatures / levels Total 7 7 of

8 4(a) The noble gases AO.4c 4(b)(i) horizontal line at 30 K allow +/- ½ square (for height) 4(b)(ii) any value in the range (K) 4(b)(iii) allow any width up to 2 cm AO2.4c AO2.4c AO3.4c 4(c)(i) liquid radon AO quite close / just touching do not accept regular.a radon gas widely spaced / large gaps 4(c)(ii) liquid radon AO random / slow / free radon gas allow random or free as a description only once.a random / rapid / free Total 8 8 of

9 5(a)(i) covalent AO2 2.2c 5(a)(ii) By gaining one electron AO2 2.c, 2.e 5(b)(i) High melting point AO 2.2a 5(b)(ii) water allow in a liquid or in solution AO 2.2b 5(c)(i) ClO 3 - AO2.3a 5(c)(ii) g must be in this order AO aq.3e 5(c)(iii) 3 AO2.3d 5(c)(iv) 06.5 correct answer with or without working gains 2 marks if answer incorrect allow mark for either: Na + Cl + O = 74.5 or 3x6 = 48 2 AO2.3b Total 0 9 of

10 6(a)(i) carbon dioxide / CO 2 water / H 2 O either order AO.3d, 4.3b 6(a)(ii) acid in beaker or stir or add solid in small amounts ignore heat 3 AO / 2 AO2 add excess (magnesium carbonate to sulfuric acid) allow until no more reacts 4.2a, 4.2b filter off excess magnesium carbonate heat / evaporate (filtrate/solution) allow to cool / crystallise allow 2 marks for: partially evaporate or leave to evaporate 6(b) (precipitate) lead chloride allow mark for reverse order AO3 (solution) sodium nitrate 4.2c Total 9 0 of

11 7(a)(i) hot / heat(ed) allow high temperature or temperature in range O C AO 8.a catalyst allow mixed with steam or at high pressure 7(a)(ii) Thermal decomposition AO 8.a 7(b)(i) any two from: (is a) liquid (which is) less dense does not mix or does not dissolve in water or immiscible ignore does not react ignore viscosity 2 AO3 8.b 7(b)(ii) (before) orange / yellow / brown (solution) (after) to colourless / decolourised ignore red ignore clear AO 8.d 7(b)(iii) (alkanes) fuels AO (alkenes) making polymers allow making plastics / ethanol 8.e 7(c) (5x) single bonds between the three carbon atoms and a single bond to each of the hydrogens AO2 8.2a two trailing / connecting bonds n at the bottom right corner of the bracket would score 3 marks Total 2 of