WJEC Chemistry for AS Level Student Book: 2nd Edition

Examinations Two units will be examined at AS Level. The assessment is summarised in the table below: Paper Unit 1 The Language of Chemistry, Structure of Matter and Simple Reactions Unit 2 Energy, Rate and Chemistry of Carbon Compounds Topics covered Topic 1.1–1.7 Topic 2.1–2.8 % of the AS quali cation 50% 50% Length of exam 1 hour 30 minutes 1 hour 30 minutes Marks available 80 80 Question types Short answer Structured Calculation Extended prose Short answer Structured Calculation Extended prose Practical A minimum of 15% of the marks across both papers will be awarded for practical knowledge and understanding Maths A minimum of 20% of the marks across both papers will be awarded for mathematics at Level 2 Examination questions As well as being able to recall facts, write equations, name structures and describe their functions, you need to appreciate the underlying principles of the subject and understand associated concepts and ideas. In other words, you need to develop skills so that you can apply what you have learned, even to situations not previously encountered. You will be expected to answer different styles of question, for example: ▪ Short answer questions – these require a brief answer, such as a formula, an equation, an observation or a de nition. ▪ Structured questions – these are in several parts, often about a common theme. They can become more dif cult as you work your way through. Structured questions can be short, requiring a brief response, or may include the opportunity for extended writing. The number of lined spaces and the mark allocation at the end of each part question are there to help you. They indicate the length of answer expected. If three marks are allocated then you must give at least three separate points. ▪ Calculations – you may be asked to convert between units, rearrange formulae and equations, analyse and evaluate numerical data or inter-convert numerical data and graph form. Although these mathematical questions account for a minimum of 20% of the total mark, this does not mean 20% in each paper. Unit 1 will carry a greater percentage of maths marks than Unit 2. ▪ Extended prose question – each paper will contain one six- mark question which requires extended prose for its answer. Often, candidates rush into such questions. You should take time to read it carefully to discover exactly what the examiner requires in the answer, and then construct a plan. This will not only help you organise your thoughts logically but will also give you a checklist to which you can refer when writing your answer. In this way you will be less likely to repeat yourself, wander off the subject or omit important points. Examiners do not award marks for individual items of information, but a more holistic approach using a banded level of response is used. 5–6 marks will be awarded if you include most of the relevant factual information with clear scienti c reasoning. The piece of writing should answer the question directly, using well- constructed sentences and suitable chemical terminology. 3–4 marks will be awarded if there are some factual omissions. 1–2 marks will be awarded if only a few valid points are made, with little use of scienti c vocabulary. 0 marks will be awarded if the question is not attempted or no relevant points are made. Since practical work is an essential part of chemistry, questions assessing your practical knowledge and understanding can be part of any style of question, e.g. giving an observation in a short answer question, explaining how re ning an experiment can improve the result as part of a structured question or planning an experiment in an extended prose question. Command words Command words are just the part of the question that tell you what to do. You’ll nd answering the exam questions much easier if you understand exactly what they mean. The most common command words are summarised in the table below: Command words What to do Give/Name/ State Give a one-word answer or a short sentence with no explanation. State what you see/Describe an observation Write about what you would expect to happen in a reaction, e.g. effervescence seen, a white precipitate forms. Describe or outline an experiment Give a step-by-step account of what is taking place. Include any equipment you would use, the reagents required and any reaction conditions. Explain Give chemical reasons for something. Suggest/ Predict There may not be a de nite answer to the question. Use your chemical knowledge to put forward a sensible idea to what the answer might be. Compare Give the similarities and/or differences between two things. Make an explicit comparison in each sentence. Deduce Use the information provided to answer the question. Calculate Use the information provided and your mathematical knowledge to work out the answer. Justify You will be given a statement for which you should use your chemical knowledge as evidence in support or to the contrary. Draw a conclusion as to whether the initial statement can be accepted. Write an equation You will need to know the formulae of the reactants and products. Also, you must ensure that the equation is balanced. 8 WJEC Chemistry for AS Level