AS LEVEL AND A LEVELCHEMISTRY



AS Level ChemistryStudent Study Guide(2013 - 2014)ContentsPageIntroduction3Specification3Course requirements4Course structure5Teaching and learning strategies6Resources8Subject expectations9(a)Our expectations(b)Your entitlementAssessment10Work out of the classroom11Information technology11Appendix 1 (Aggregation – your final grade)12Appendix 2 (Subject specific skills)13Appendix 3 (Practical work)14Appendix 4 (Skills assessment)15Appendix 5 (Module Examinations)16Appendix 6 (List of all sub-modules)17Appendix 7 (Practical Skills in Chemistry)19IntroductionThis is your guide to AS level chemistry. It is an important document that will aid you in your studies during the one or two years. It contains details about many of the questions you will have about the course such as;How will I be assessed in AS level chemistry?Will I have any coursework to do?How much work should I do?What help can I expect?When will I take my external examinationsWhat are the examinations like?Can I retake any of my examinations?Do not lose your study guide. Read it carefully at the start of and during the course.SpecificationAS levelA copy of the specification can be obtained from the web site RequirementsYou will have obtained a grade C or above in IGCSE Chemistry.If you have entered the school from a differetn exam board you will need to consult with the Head of Chemistry, to seek his permission to take AS Chemistry. You are likely to be asked to complete a contract regarding your work and your progress will be reviewed after 6 weeks in the subject.Course structureFor AS level you will have to study three modules of work. AS level Chemistry ModulesAS level Chemistry comprises of three modules.ModuleModule titleTest dateRe-take test date*F321Atoms, bonds and groupsMay/June 2014May /June 2015F322Chains, energy and resourcesJune 2014June 2015F323Practical skills in Chemistry 1Throughout year* This re-take will mean you have to study for both the AS and A2 level exams at the same time and is very difficult – Do not rely on this!Each module is split into various sub-modules. For example the Chains, Energy and Resources module is split into 1 sub-modules labelled CER1 to CER13. Each sub-module has its own criteria sheet that includes a list of the assessment outcomes (the things that you must be able to do in an examination). The criteria sheet will always list the test requirements as well as any practical requirements. Sub-modules are normally between 2 lessons and 12 double lessons in length.The use of criteria sheets will allow you to get used to the change from IGCSE Chemistry to AS level Chemistry. Teaching and Learning StrategiesA wide variety of teaching and learning strategies are employed that are designed to get you to participate fully in lessons. Teaching and learning strategies will also help to develop your key skills. The strategies employed include:DiscussionQuestion and answer sessionsIndependent learning schemesLecture - talk and chalkVideoComputer simulationsProblem solving - planning and designIndustrial visitsTrips to colleges and/or universitiesPractical demonstrationsPractical investigationsSmall group tutorialsIndividual tutorials.Student talks and lessonsWhiteboard presentationsA varied approach to teaching strategies is used to try to get the best from you. Your chemistry teachers will do their best but the motivation and enthusiasm must come from you.Practical workPractical work is an essential element of the AS level Chemistry course. It is assessed during the course by practical assessments carried out in examination conditions. It is important that during the course you develop practical skills that allow you to complete experiments accurately, efficiently and safely. Some of the skills you have already mastered others will be new to you.The purpose of the practical work is to:Illustrate the theory workTo develop the practical skills needed for the skills assessment (coursework)Develop investigative and planning skills.Practical work will be regularly marked and you will be expected to follow the set of instructions given in appendix 3.Student presentationsWhen you study AS level Chemistry you will be expected to give a talk or presentation on some aspect of chemistry. It may be a short 15 minute explanation or a longer extended talk. It sounds daunting but it will allow you to collect evidence for some key skills and develop your confidence to be able to communicate your ideas clearly to others. Independent LearningWhen you study AS level Chemistry at least one section of the course will involve independent learning. You will be provided with a study guide, all necessary criteria, and your teacher will be one of your resources. It is a challenging opportunity for you to develop your skills of organisation, and handling data. You will of course be expected to read about the topics taught and to make your own notes and supplement those given by your teacher. You should expect to show a great deal of independence in terms of the way that you tackle the workload presented. A reading list and log will be provided for you to record your independent readings.ResourcesTextbooksThere are lots of textbooks although many of these are not specifically written for this course. You will be provided with an OCR AS Chemistry textbook and an OCR AS revision guide. LibraryThe library is well equipped with reference books some of which are available for overnight loan.3Videos and CDsThe chemistry department has some CDs and videos that you may be able to borrow. Please do not hesitate to ask Mr Shead.4Your teacherProbably your most important resource of all. We expect you to ask questions and demand of our time.Subject Expectations and EntitlementsOur expectationsIt is expected that you will;(i)Fulfil the requirements and expectations of your teachers;(ii)Consult regularly with your chemistry teachers about your progress both in and out of lesson time;(iii)Immediately seek advice and help when you have problems and difficulties;(iv)Use and read this document;(v)Store and use the criteria sheet for every sub-module - it will eventually provide you with the complete AS level specification;(vi)Follow the instructions in the practical work guidelines in the appendix;(vii)Complete subject reviews sensibly and enthusiastically;(viii)Complete any self assessment or key skill exercise enthusiastically; (ix)Complete all homework exercises by the deadline set.(x)Carry out about five to six hours chemistry work outside of lesson times. This should include homework, copying up notes and background plete all past papers setYour entitlementIn return you can expect that your chemistry teachers will;(i)Set and mark homework regularly and provide model answers to exercises set;(ii)Provide interesting and stimulating lessons;(iii)Not cancel lessons unnecessarily;Be available for consultation, advice and help;Mark all past papers set and hand them back as soon as possible and make available model answers for the past papers.Provide regular and informative feedbackAssessmentYou will have skills assessments that counts towards the AS level grade. The skills assessment involves working on one of three aspects of practical work where you are given a task to complete within a lesson.The other aspect of assessment in AS level Chemistry is the module examinations you will take. The combined scores of all your modules examination results will make up your final grade at A or AS level. During the AS level course you will have regular testing and all homework will be assessed.RetakesYou can retake some Module examinations that you fail or do not do very well in. There is a schedule of Module examinations shown in appendix 1. When you retake a module examination it is the better score that is used to work out your final grade. You should only enter for a re-take after seeking advice from your teacher and only if you are prepared to work extremely hard on the module you are re-taking. There is no use re-taking a module and getting a lower mark.Criteria sheetsSince you are used to units and end of unit tests from IGCSE Chemistry the AS level chemistry course uses a similar structure. You will be provided with a criteria sheet for each sub-module e.g. ABG1. This criteria sheet will show the;Assessment outcomes for the test – these are the things you must be able to do in a test or a module examination.Possible practical’s to be carried out together with the practical skills associated with the practical – although time restraints mean that you may not complete all of these in class.Student ReviewsYou teacher will discuss your progress with you on a regular basis and you will negotiate short and long term targets with your teachers.Work out of the ClassroomYou will need to do about 5-6 hours work out of the classroom per week. If homework is not specifically set there is always background reading or revision to do. It is much easier to revise and sort your problems out straight away than find out in an examination you cannot do it. 5 hours does mean 5 solid hours with no interruptions - it is amazing how much work you can get done in that time.Homework will be regularly set normally in the form of worksheets or from the textbook, you may well have practical work as well to finish. Hand in your work on time since it allows your teacher the time to mark your work and comment constructively about your efforts. Failure to hand work in at the right time may result in it not being marked. When you get your work back check and if necessary seek clarification about your errors. Don't forget you can always ask for the mark scheme.Finally remember that you can always see your teacher for help before you hand your work in.RevisionSuccess in AS level Chemistry will depend on how much revision you do. Students who complete all the past papers set and use a revision plan are much more likely to get the grade of which they are capable than those students who do not complete the past papers and revise rmation Communication TechnologyDuring your time taking AS-level Chemistry you will be expected to take full advantage of the ICT facilities within the department. From time to time you will be set exercises that require the use of ICT, sometimes it will be a familiar application on other occasions it will be new and you will require help and guidance from your teachers. It is hoped that you will develop your ability to use:data-loggers;spreadsheets;computer simulations;the Internet to research for information;CD-ROMs;desk top publishing techniques to enhance the presentation of your work;graph plotting software;PowerPointuse of the interactive whiteboard Appendix 1 - Aggregation - Your Final GradeAll your module scores are converted from the raw score (that is the actual mark – the number of ticks) into a mark on the uniform mark spine (UMS). It the UMS score that is most important because it is this that is added together to get you an AS or A level grade.UMS have to be used because this takes into account that some years a paper may be easier than another year. If raw score were used then you could find it easier to get high marks one year compared to another.AS levelYour exam score is converted into a UMS score and this score is the one reported to you on your certificates. In simple terms your final grade is worked out by taking your best UMS scores in the three modules. The maximum score possible is 300.Total scoreGrade240 – 300210 – 239180 - 209150 – 179120 – 149less than 120ABCDEUAppendix 2 - Subject Specific SkillsYou should be able to;1Locate, select, organise and present information from a variety of sources.2Handle information, distinguishing the relevant from the extraneous.3Translate information from one form to another.4Manipulate numerical and other data.5Identify patterns, report trends and draw inferences and conclusions.6Analyse and evaluate information7Present reasoned explanations for phenomena, patterns and relationships.8Make predictions and hypotheses.9Construct arguments to support hypotheses or to justify a course of action.10Apply knowledge, including principles, to new situations.11Evaluate information and hypotheses.12Plan investigations, including the identification, collection, selection and use of information from appropriate sources.13Be able to follow detailed sets or sequences of instructions.14Use techniques, apparatus and substances confidently and safely.15Make and record observations, measurements and estimates.16Interpret and evaluate observations and experimental results.17Select appropriate techniques, apparatus and materials.18Evaluate methods and suggest possible improvements to experiments.Appendix 3 - Practical Work1Before each experiment you will normally be given an instruction sheet. Read through the sheet carefully and consult your teachers if there are any problems.2Any pre-laboratory questions must be handed in before the practical. Failure to hand in these questions could result in exclusion from the practical lesson.3The experiment must be carried out as directed and experimental results and observations must be written directly into your results sheets not a scrap of paper. If possible the deductions, calculations or conclusions must also be done in the lesson.4Any post-laboratory questions must be completed and handed in.5If you intent to continue with Chemistry then you may be advised to buy a laboratory coat. Speak to Mr Shead if you are interested.See appendix 7 for further details and advise.Appendix 4 – Skills AssessmentF323 Practical Skills in Chemistry 1You must complete three different types of taskAn Evaluation task worth 15 marksA Qualitative task worth 10 marksA Quantitative task worth 15 marksYour final mark is eventually converted into a UMS score out of 60GradeUMS scoreABCDE48 - 6042 - 4736 - 4130 - 3524 - 29There are three evaluation tasks, three qualitative tasks and three quantitative tasks. You may attempt all available tasks and the best score for each type of task will count.The module can be repeated in the A2 year but only new tasks can be attempted.The tasks are done in examination conditions and marked according to the mark scheme provided by OCR. Your teacher cannot give specific feedback other than the mark awarded. Appendix 5 – Module ExaminationsF321 Atoms, Bonds and GroupsDate:May/June 2014Re-take: May/June 2015Duration: 1 hourMaximum mark: 60Total UMS: 90The question paper contains structured questions (short answer questions) that account for about 45 marks and questions involving more extended answers that account for about 15 marks. A quality of written communication mark (which includes spelling, punctuation and grammar) is awarded in a question that requires a more extended answer.GradeUMS scoreABCDE72 - 9063 - 7154 - 6245 - 5336 - 44F322 Chains, Energy and ResourcesDate:June 2014Re-take:June 2015Duration: 1 hour 45 minutesMaximum mark: 100Total UMS: 150The question paper contains structured questions (short answer questions) that account for about 75 marks and questions involving more extended answers that account for about 25 marks. A quality of written communication mark (which includes spelling, punctuation and grammar) is awarded in a question that requires a more extended answer.GradeUMS scoreABCDE120 - 150105 - 11990 - 10475 - 8960 - 74 Appendix 6 – List of all the sub-modulesModule F321 Atoms, Bonds and Groups (AS module)Essential requirementsGrade C in IGCSE ChemistryGrade C in GCSE MathematicsSub-ModulesABG1Basic calculations and conceptsABG2Oxidation Numbers and Redox ABG3Mass spectroscopyABG4Atomic structureABG5Covalent and ionic bondingABG6StructureABG7Ionisation EnergyABG8Periodicity and the Periodic TableABG9 Acids and SaltsABG10 Group 2ABG11Group 7Module F322 Chains, Energy and Resources (AS Module)Essential requirementsGrade C in IGCSE ChemistrySub-modulesCER1Introduction to Organic ChemistryCER2Atom Economy and Percentage YieldCER3AlkanesCER4Crude oil, fuels and petrochemicalsCER5AlkenesCER6Addition polymersCER7HalogenoalkanesCER8AlcoholsCER9Infra-red Spectroscopy and Mass SpectrometryCER10Enthalpy ChangesCER11Qualitative reaction kineticsCER12Dynamic Equilibrium and Le Chatelier’s PrincipleCER13Chemistry of the AirModule F323 – Practical Skills in Chemistry 1 (AS Module)Essential requirementsGrade C in IGCSE ChemistryGrade C in GCSE MathematicsTasksEvaluationQualitativeQuantitativeAppendix 7Practical skills and assessment 20% of EOY mark The key skills that are being assessed:? develop good laboratory technique;? make and record accurate measurements and observations;? interpret the results of experiments to form theories or conclusions;? establish whether data collected from experiments is valid and reliable;? evaluate experimental technique and scientific method in light of practical experience;? gain knowledge of laboratory safety and the safe use of chemicals;? learn the importance of careful waste chemical disposal and the potentially harmful effects of chemicals on the environment.Remember there are three tasks; Qualitative, Quantitative and Evaluative.Qualitative Tasks (10 marks)Candidates should be able to:? identify any hazards in the chemicals to be used or made, noting down appropriate control measures (e.g. fume cupboard, eye protection, protective gloves, extinguishing naked flames);? handle safely flammable, corrosive, toxic and harmful materials, including solids, liquids and gases;? use appropriate techniques, reagents and apparatus to complete suitable activities;? manipulate standard laboratory apparatus safely and with confidence to produce accurate data;? record all suitable observations and data in an appropriate format and to an appropriate degree of accuracy, taking into consideration the apparatus used;? use and record the correct units for all measurements taken;? provide simple conclusions based on the observations made.Quantitative Tasks (15 marks)Candidates should be able to:? carry out quantitative experiments with appropriate care and precision;? make and record measurements reliably and accurately;? perform calculations, based on their practical work;? use units accurately;? use appropriate numbers of significant figures consistent with their least accurate measurement;? construct and interpret appropriate graphs from data collected or provided;? reach a valid conclusion based upon the data obtained from experiments.Evaluative Tasks (15 marks)Candidates should be able to:? recognise anomalous results on the basis of measurements taken or provided;? identify the limitations of accuracy in experimental procedures;? recognise that some errors may be inherent in the apparatus used;? calculate percentage errors involved in measurements taken using:(i) volumetric flasks, pipettes and burettes,(ii) measuring cylinders, thermometers and balances;? evaluate both the procedural and measurement errors associated with a particular experiment and comment on the most significant errors;? suggest sensible improvements to experimental procedures and the taking of measurements based on their laboratory experience? reach a valid conclusion based upon the data obtained from experiments.Useful termsAccuracy is a measure of the closeness of agreement between an individual test result and the accepted reference value. If a test result is accurate, it is in close agreement with the accepted reference value.Error (of measurement) is the difference between an individual measurement and the true value (or accepted reference value) of the quantity being measured.Precision is the closeness of agreement between independent measurements obtained under the same conditions. It depends only on the distribution of random errors (i.e. the spread of measurements) and does not relate to the true value.Uncertainty is an estimate attached to a measurement which characterises the range of values within which the true value is asserted to lie. This is normally expressed as a range of values such as 44.0 ± 0.4.Reliability is the opposite of uncertainty, i.e. if the uncertainty is great; the measurement is not very reliable.How accurate are measurements?When using a digital measuring device (such as a modern top pan balance or ammeter),? record all the digits shown.When using a non-digital device (such as a ruler or a burette),? record all the figures that are known for certain plus one that is estimated.As a general rule, the uncertainty is often taken to be half a division on either side of the smallest unit on the scale you are using. However, the accuracy of measurements does also depend on the quality of the apparatus used, such as a balance, thermometer or glassware.For example, a 100 cm3 measuring cylinder is graduated in divisions every 1 cm3.? A Class A measuring cylinder has a maximum error of half a division or 0.5 cm3? A Class B measuring cylinder has a maximum error of a whole division or 1 cm3.Because of this variability, assessed Tasks will state the maximum error in any measurement thatis being made.Examples of maximum errorsWhen glassware is manufactured there will always be a maximum error. This is usually marked on the glassware.Some examples are shown below. Note that the actual maximum error on a particular item of glassware may differ from the values given below.Volumetric or standard flask (Class B)? A 250 cm3 volumetric flask has a maximum error of 0.2 cm3 or 0.08%.Pipette (Class B)? A 25 cm3 pipette has a maximum error of 0.06 cm3 or 0.24%.Burette (Class B)? A pipette has a maximum error of 0.05 cm3 in each measurement.Some examplesThe significance of the maximum error in a measurement depends upon how large a quantity isbeing measured. It is useful to quantify this error as a percentage error.Percentage error = maximum error / quantity measured × 100%For example, a two-decimal place balance may have a maximum error of 0.005 g.For a mass measurement of 2.56 g,? percentage error = 0.005/2.56 ×100% = 0.20%? For a mass measurement of 0.12 g, the percentage error is much greater:Percentage error = 0.005/0.12 ×100% = 4.2%Multiple measurementsFor multiple measurements using the same two-decimal place balance, there will be a maximum error of 0.005 g for each measurement.For two mass measurements that give a resultant mass by difference, there are two maximum errors:Percentage error = 2 × maximum error in each measurement/quantity measured × 100%For example, using the same two-decimal place balance,Mass of crucible + crystals before heat = 23.45 g maximum error = 0.005 gMass of crucible + crystals after heat = 23.21 g maximum error = 0.005 gMass lost = 0.23 g maximum overall error = 2 x 0.005 gThere is a negligible percentage error in each mass measurement but the overall error in mass loss is much greater:Percentage error in mass loss = 2 × 0.005/0.23 × 100% = 4.3%Reading burettesA burette is graduated in divisions every 0.1 cm3.A burette is a non-digital device, so we record all figures that are known for certain plus one that is estimated.Using the half-division rule, the estimation is one of 0.05 cm3. We therefore record burette measurements to two decimal places with the last figure either ‘0’ or ‘5’.The maximum error in each measurement = 0.05 cm3.The overall maximum error in any volume measured always comes from two measurements, sothe overall maximum error = 2 x 0.05 cm3 = 0.1 cm3.In a titration, a burette will typically deliver about 25 cm3 so the percentage error is small.? Percentage error = 2 × 0.05/25.00 × 100% = 0.4%For small volumes, the percentage error becomes more significantFor delivery of 2.50 cm3,? percentage error = 2 × 0.05/2.50 × 100% = 4%Recording volumes during titrationsAs shown above, each burette measurements should be recorded to two decimal places with the last figure either ‘0’ or ‘5’.During a titration, it is expected that students will record both initial and final burette readings from which a titre is calculated by difference. It is usual practice to record titration results in a table of the type shown below.trial123final burette reading / cm3initial burette reading / cm3titre / cm3titres used to calculate mean (tick)mean titre / cm3When recording the titre, it is normal practice to use two decimal places. This is what will beexpected within the assessment Tasks.Mean titresWhen recording a mean titre, is usual practice to take an average of the concordant titres, i.e.those that agree to within 0.10 cm3. Where this is not possible, the two titres that have the closestagreement should be used.For example, three recorded titres are 25.80 cm3, 25.30 cm3 and 25.20 cm3.The mean titre is the average of the 2nd and 3rd titres which agree to within 0.1 cm3.? The mean titre is (25.30 + 25.20)/2 cm3 = 25.25 cm3The overall maximum error is 2 x 0.05 = 0.1 cm3.There is a case for arguing that the accumulated errors indicate that one decimal place is more appropriate but this should not be used. The maximum error is the worst-case scenario and it is likely that the actual titre will in reality be more accurate than one decimal place.A student obtaining concordant titres within 0.05 cm3 of one another may encounter a problemwhen calculating the mean titre. For example, a student may obtain three recorded titres of 25.80cm3, 25.25 cm3 and 25.20 cm3.The mean titre is (25.25 + 25.20)/2cm3 = 25.225 cm3This mean titre has a value that is more accurate than the burette can measure. The value of25.225 cm3 should more correctly be ‘rounded’ to 25.25 cm3 OR WHATEVER is asked for in the assessment.It would seem very unfair not to credit a mean titre of 25.225 cm3 in this case, especially as thisstudent has carried out the titration better than the first student.How many significant figures should be used?The result of a calculation that involves measured quantities cannot be more certain than the least certain of the information that is used. So the result should contain the same number of significant figures as the measurement that has the smallest number of significant figures.A common mistake by students is to simply copy down the final answer from the display of a calculator. This often has far more significant figures than the measurements justify.Rounding offWhen rounding off a number that has more significant figures than are justified (as in the example above), if the last figure is between 5 and 9 inclusive round up; if it is between 0 and 4 inclusive round down.For example, the number 350.99 rounded to:4 sig fig is 351.03 sig fig is 3512 sig fig is 3501 sig fig is 400Notice that when rounding you only look at the one figure beyond the number of figures to which you are rounding, i.e. to round to three sig fig you only look at the fourth figure.How do we know the number of significant figures?In the example above, 351 has been rounded to the 2 sig fig value of 350.However, if seen in isolation, it would be impossible to know whether the final zero in 350 issignificant (and the value to 3 sig figs) or insignificant (and the value to 2 sig figs).In such cases, standard form should be used and is unambiguous:? 3.5 x 102 is to 2 sig figs? 3.50 x 102 is to 3 sig figsWhen to round offIt is important to be careful when rounding off in a calculation with two or more steps.? Rounding off should be left until the very end of the calculation.? Rounding off after each step, and using this rounded figure as the starting figure for thenext step, is likely to make a difference to the final answer. This introduces a roundingerror.Students often introduce rounding errors in multi-step calculations.ExampleWhen 6.074 g of a carbonate is reacted with 50.0 cm3 of 2.0 mol dm–3 HCl(aq) (which is anexcess), a temperature rise of 5.5 °C is obtained. The specific heat capacity of the solution is 4.18J g–1 K–1,The heat produced = 50.0 × 4.18 x 5.5 for which a calculator gives 1149.5 J = 1.1495 kJSince the least certain measurement (the temperature rise) is only to 2 significant figuresthe answer should also be quoted to 2 significant figures.Therefore, the heat produced = 1.1 kJ? It should be noted however, that if this figure is to be used subsequently to calculate theenthalpy change per mole then the rounding off should not be applied until the final answerhas been obtained.For example, if the carbonate has a molar mass of 84.3 g mol–1, the enthalpy change per mole ofcarbonate can be calculated from the value above.Using the calculator value of 1.1495 kJ for the heat produced, ? enthalpy per mole = 15.95371255 kJ mol–1.? rounding to 2 sig figs gives 16 kJ mol–1Using the rounded value of 1.1 kJ for the heat produced,? enthalpy per mole = 15.26671057 kJ mol–1.? rounding to 2 sig figs gives 15 kJ mol–1 and we have a ‘rounding error’.Errors in procedureThe accuracy of a final result also depends on the procedure used. For example, in an enthalpyexperiment, the measurement of a temperature change may be precise but there may be largeheat losses to the surroundings which affect the accuracy of overall result.Anomalous readingsWhere an experiment uses repeated measurements of the same quantity, such as repeatedtitration readings, anomalous readings should be identified. If a titre is clearly outside the range ofall other readings, it can be judged as being anomalous and should be ignored when the mean titreis calculated.Similarly, if a plotted graph reveals that a value is anomalous, then it should be ignored. ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download