OCR CHEMISTRY (SALTERS)

A2 – INDIVIDUAL INVESTIGATION

Additional Guidance for Teachers

The notes below are intended to complement the sections about the A2 Individual Investigation within the OCR publication ‘Notes for the Guidance of Teachers on the Assessment of Practical Skills, Chemistry (Salters), 3887, 7887’, published in Spring 2000.

Some General Points

Candidates can base their investigation on any aspect of chemistry. The choice of topic, however, should allow them to demonstrate their abilities against the descriptors in all four, skill areas.

The investigation must contain a significant synoptic component. That is, candidates must draw together chemical ideas from different parts of the specification and apply them in the context of the investigation. To satisfy level 5 in planning and analysing, candidates must make use of ideas drawn from different parts of the specification. To satisfy level 8 the candidate must make use of ideas drawn from more than one module. Here, module means the work covered for each of the units of assessment i.e. Chemistry for Life (2850), Minerals to Medicines (2851) etc., it does not mean individual teaching units in the course such as EL, DF etc. To satisfy level 11 the candidate must make use of ideas drawn from both the AS and A2 parts of the specification. These requirements are clearly indicated in the OCR specification. The wording of in the ‘Notes for the Guidance of Teachers in the Assessment of Practical Skills’ is less specific about the meaning of the synoptic requirement. The wording in the OCR specification should be followed.

Many investigations will fulfil the synoptic requirement automatically. It is necessary, however, for candidates to explicitly show how they fulfil this requirement within their written report and for teachers to check on this while marking it.

Changing a number of variables in an investigation will often help satisfy the synoptic requirement. It is not, however, essential to do this. If a candidate uses a range of chemical ideas from different parts of the specification in an investigation which focuses on a single variable then this is equally acceptable and may often be the preferred approach.

The teacher assessment of the investigation should take account of the level of demand of the activities undertaken by the candidate. Investigations that make few demands on the manipulative and thinking skills of candidates will not easily allow them to access the higher mark levels.

Every investigation should generate a body of evidence that can be processed and evaluated. In most cases this means that the investigation will contain a significant quantitative component. It is likely that investigations comprised largely of organic synthesis will not provide sufficient opportunities for candidates to demonstrate their abilities when measured against the descriptors in the four skill areas.

There is significant emphasis within the assessment descriptors on the need for the evidence collected by the candidate to be accurate and reliable. It is vital, therefore that candidates critically review each set of data as soon as it has been collected to help decide, for example, whether additional data points are required or whether particular experiments should be repeated. To achieve the highest mark levels, candidates should concentrate on the quality rather than the quantity of the evidence gathered.

The nature of the conclusions drawn in the analysis skill area will depend on the type of investigation undertaken. Investigations of reaction kinetics, for example, may lead to precise conclusions about order of reaction, activation enthalpy or reaction mechanism. Analytical investigations may lead to conclusions about the composition of materials. Other types of investigation may lead to more general conclusions about the patterns identified in the evidence collected.

When a teacher is assessing an individual investigation it is not necessary for a detailed mark scheme to be drawn up, as is the case in the assessment of AS Experimental Skills. Teachers should base their assessment on the general descriptors found in Appendix E of the OCR Chemistry (Salters) specification, bearing in mind that this assessment is part of the A2 component of the specification.

Each skill area is made up of two assessment strands. Different investigations may place greater emphasis on one or other of the strands in a particular skill area but the candidate must show some achievement in each both strands of all skill areas.

Teachers should annotate the written report to identify where it meets particular descriptors. A particularly helpful strategy to ensure the award of an appropriate mark is for teachers to add a brief comment at the end of each skill area indicating why a particular mark has been awarded and why a higher mark was not appropriate. So, for example, where a teacher feels that a planning section should be awarded a mark of 10, moderators would expect to see several of the annotations 2a, 2b, 5a, 5b, 8a, 8b at various places on the plan and also a few 11a and/or 11b annotations with a final note to indicate why a mark of 10 and not 11 was awarded.

What is needed by students in the planning section to access the whole mark range

This section should start with a statement of the aims of the investigation.

The main bulk of this section will be made up of a detailed account of practical work carried out by the candidate. This will have been updated during the course of the investigation to include any modifications made in procedures.

Sufficient theory should be included to explain why particular experiments are planned and to indicate the useful evidence that they should generate.

An explanation should also be included of why particular amounts of materials have been used and why particular choices in the plan, for example, numbers of experiments and repeated experiments, have been made to ensure accurate and reliable data.

It is necessary for the candidate to show that they have met the synoptic requirement of this assessment component. A straight forward way of doing this is for them to construct a table linking the chemical ideas which they have used to the modules of the specification in which these ideas are covered.

A risk assessment must be included in the plan. This should identify the hazards associated with materials used or produced and the procedures used during the investigation and should indicate the precautions that should be taken because of these hazards.

The planning section should end with a bibliography in which the resources that have been used in devising the plan are listed in sufficient detail so that someone else could easily look them up. Sections of the plan should be linked to the appropriate reference in the bibliography, for example by a system of numbers.

What is needed by students in the implementing section to access the whole mark range

Teachers should assess the candidates’ manipulative skills by direct observation in the laboratory during the course of the investigation. Teachers should make a written note of these observations that can be used to support the mark awarded under this strand of the assessment.

Candidates should record their results in clearly labelled tables using appropriate units. It may well be helpful to link the tables to relevant sections of the plan using explanatory sub-headings. All measurements and observations should be included, not simply averaged values.

What is needed by students in the analysis section to access the whole mark range

Steps in calculations should be clearly shown and explained rather than an answer emerging from a jumble of figures.

Graphs should be appropriate to the activity with clearly labelled axes and appropriate units.

Conclusions should be drawn from the evidence gathered using chemical ideas described in the planning section.

What is needed by students in the evaluation section to access the whole mark range

Candidates should try to estimate how accurate and reliable is the evidence that they have collected.

Percentage errors should be calculated for all measurements where this is possible.

Errors associated with procedures should be identified and the effects that they might have on the overall results considered.

A comparison of the magnitude of errors should lead to a view about which of them is likely to have the most significant impact on the evidence collected.

Candidates should suggest ways in which they could improve their investigation where this is appropriate. This should not include modifications that could have been made by the candidate during the course of the investigation and they should be realistic in the context of the facilities available to the candidate. Alternatively, the candidate should identify those aspects of the investigation that were vital in ensuring that the evidence collected was accurate and reproducible.

1