PHYSICAL SCIENCES: CHEMISTRY (P2) NOVEMBER 2010 MEMORANDUM

1 Copyright reserved Please turn over MARKS: 150 This MEMORANDUM consists of 16 pages. PHYSICAL sciences : CHEMISTRY (P2) NOVEMBER 2010 MEMORANDUMNATIONAL SENIOR CERTIFICATEGRAAD 12 GRADE 12 PHYSICAL sciences /P2 2 DBE/ NOVEMBER 2010 NSC MEMORANDUM Copyright reserved Please turn over Learning Outcomes and Assessment Standards LO 1 LO 2 LO 3 AS : Design, plan and conduct a scientific inquiry to collect data systematically with regard to accuracy, reliability and the need to control variables.

2 AS : Seek patterns and trends, represent them in different forms, explain the trends, use scientific reasoning to draw and evaluate conclusions, and formulate generalisations. AS : Select and use appropriate problem-solving strategies to solve (unseen) problems. AS : Communicate and defend scientific arguments with clarity and precision. AS : Define, discuss and explain prescribed scientific knowledge. AS Express and explain prescribed scientific principles, theories, models and laws by indicating the relationship between different facts and concepts in own words. AS : Apply scientific knowledge in everyday life contexts.

3 AS : Research, discuss, compare and evaluate scientific and indigenous knowledge systems and knowledge claims by indicating the correlation among them, and explain the acceptance of different claims. AS : Research case studies and present ethical and moral arguments from different perspectives to indicate the impact (pros and cons) of different scientific and technological applications. AS : Evaluate the impact of scientific and technological research and indicate the contribution to the management, utilisation and development of resources to ensure sustainability continentally and globally.

4 PHYSICAL sciences /P2 3 DBE/ NOVEMBER 2010 NSC MEMORANDUM Copyright reserved Please turn over GENERAL GUIDELINES 1. CALCULATIONS Award marks for: correct formula, correct substitution, correct answer with unit. Do no award any marks if an incorrect or inappropriate formula is used, even though there may be relevant symbols and applicable substitutions. When an error is made during substitution into a correct formula, award a mark for the correct formula and for the correct substitutions, but do not give any further marks.

5 If no formula is given, but all substitutions are correct, the candidate forfeits one mark. Example: No Kc expression, correct substitution Kc = 32)1)(2()2(3 = 2 3 (32) Marks can only be allocated for substitutions when values are substituted into formulae and not when listed before a calculation starts. All calculations, when not specified in the question, must be done to two decimal places. 2. UNITS Candidates must be penalised only once for the repeated use of an incorrect unit within a question or subquestion. Units are only required in the final answer to a calculation.

6 Award marks for an answer only, and not for a unit per se. Candidates forfeit the mark allocated for the answer in each of the following situations: - Correct answer + wrong unit - Wrong answer + correct unit - Correct answer + no unit Separate compound units with a multiplication dot, not a full stop, for example, mol dm-3. Accept (or mol/dm3) for marking purposes 3. GENERAL If one answer or calculation is required, but the candidate gives two, mark only the first one, irrespective of which one is correct. If two answers are required, mark only the first two, etc.

7 PHYSICAL sciences /P2 4 DBE/ NOVEMBER 2010 NSC MEMORANDUM Copyright reserved Please turn over When a chemical FORMULA is asked, and the NAME is given as answer the candidate forfeits the marks. The same rule applies when the NAME is asked and the FORMULA is given. When redox half-reactions are to be written, the correct arrow should be used. If the equation H2S S + 2 H+ + 2e- (22) is the correct answer, the marks must be given as follows: H2S S + 2 H+ + 2e- (21) H2S S + 2 H+ + 2e- (20) S + 2H+ + 2e- H2S (22) S + 2H+ + 2e- H2S (20) When candidates are required to give an explanation involving the relative strength of oxidising and reducing agents, do not accept the following: Stating the position of a substance on table 4 only ( Cu is above Mg).

8 Using relative reactivity only ( Mg is more reactive than Cu). The correct answer would be for instance: Mg is a stronger reducing agent than Cu, and therefore Mg will be able to reduce Cu2+ ions to Cu. The answer can also be given in terms of the relative strength as electron acceptors and donors. One mark is forfeited when the charge of an ion is omitted per equation.(not for the charge on an electron) The error carrying principle does not apply to chemical equations or half reactions. For example, if a learner writes the wrong oxidation/reduction half-reaction in the sub-question and carries the answer to another sub-question (balancing of equations or calculation of cellE) then the learner must not be credited for this substitution.

9 In the structural formula of an organic molecule all hydrogen atoms must be shown. Marks must be deducted if hydrogen atoms are omitted. When a structural formula is asked, marks must be deducted if the learner writes the condensed formula. When an IUPAC name is asked and the candidate omits the hyphen ( instead of pent-1-ene or 1-pentene the candidate writes pent 1 ene or 1 pentene), marks must be forfeited. When a chemical reaction is asked, marks are awarded for correct reactants, correct products and correct balancing. PHYSICAL sciences /P2 5 DBE/ NOVEMBER 2010 NSC MEMORANDUM Copyright reserved Please turn over If only a reactant(s) followed by an arrow, or only a product(s) preceded by an arrow, is/are written, marks may be awarded for the reactant(s) or product(s).

10 If only a reactant(s) or only a product(s) are written, without an arrow, no marks are awarded for the reactant(s) or product(s). Examples: N2 + 3H2 3 2NH3 3 bal. 3 N2 + H2 3 31 NH3 3 31 N2 + H2 30 NH3 30 4. POSITIVE MARKING Positive marking regarding calculations is followed in the following cases: Subquestion to subquestion: When a certain variable is calculated in one sub-question ( ) and needs to be substituted in another ( or ), if the answer for is incorrect and is substituted correctly in or , full marks must be awarded for the subsequent sub-questions.