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3.8 Guidance on Internal Assessment

Introduction

The GCE Sciences share a common approach to centre assessment. This is based on the belief that assessment should encourage practical activity in science, and that practical activity should encompass a broad range of activities. This section must be read in conjunction with information in the Teacher Resource Bank.

Practical and Investigative Skills are assessed in Unit 3 and Unit 6, worth, respectively, 20% of the AS Award (and 10% of the Advanced Level Award) and 10% of the full Advanced Level Award.

There are two routes for the assessment of Practical and Investigative Skills

Both routes to assessment are available at AS and A2.

3.8.1 Centre Assessed

Route T (PSA/ISA)

Each centre assessed unit comprises

The PSA consists of the centre's assessment of the candidate's ability to demonstrate practical skills throughout the course; thus, candidates should be encouraged to carry out practical and investigative work throughout the course of their study. This work should cover the skills and knowledge of How Science Works (Section 3.7) and in Sections 3.3 and 3.6.

The ISA has two stages where candidates

Each stage must be carried out under controlled conditions but may be scheduled at a time convenient to the centre. The written test must be completed in a single, uninterrupted session.

The ISA is set externally by AQA, but internally marked, with marking guidelines provided by AQA.

In a given academic year two ISAs at each of AS and A2 level will be provided.

Practical Skills Assessment (PSA)

Candidates are assessed throughout the course on practical skills, using a scale from 0 to 12. The mark submitted for practical skills should be judged by the teacher. Teachers may wish to use this section for formative assessment and should keep an ongoing record of each candidate's performance but the mark submitted should represent the candidate's practical abilities over the whole course.

The nature of the assessment

Since the skills in this section involve implementation, they must be assessed while the candidate is carrying out practical work. Practical activities are not intended to be undertaken as formal tests and supervisors can provide the level of guidance that would normally be given during teaching. In order to provide appropriate opportunities to demonstrate the necessary skills, instructions provided must not be too prescriptive but should allow candidates to make decisions for themselves, particularly concerning the conduct of practical work, their organisation and the manner in which equipment is used.

The tasks

Tasks are provided in the three areas of chemistry; inorganic, physical and organic chemistry.

AS level candidates should undertake at least two of the tasks from each of the three areas of chemistry. Each task will score a maximum of 2 marks aggregating to a total score out of 12 marks. Only marks arising from those tasks designated as AS tasks may be submitted for AS Chemistry.

A2 level candidates should undertake at least two of the tasks from each of the three areas of chemistry. Each task will score a maximum of 2 marks aggregating to a total score out of 12 marks. Only marks arising from those tasks designated as A2 tasks may be submitted for A2 Chemistry.

At both AS and A2, centres may choose to carry out all of the available tasks, in which case, the best two marks from each area for each candidate should be counted towards the final mark.

A list of the AS and A2 PSA tasks is given in Sections 3.3 and 3.6, respectively. Detailed marking guidance including descriptors for 0, 1 and 2 marks for each PSA task is provided in Section 3.8.3.

Candidates should be awarded marks which reflect their level of performance over the whole course.

AQA may wish to ask for further supporting evidence from centres in relation to the marks awarded for the PSA. Centres should therefore keep records of their candidates' performances in their practical activities throughout the course. (For example, a laboratory diary, log or tick sheet.)

Further guidance for the awarding of marks for the PSA will be provided in the Teacher Resource Bank.

Use of ICT during the PSA

Candidates are encouraged to use ICT where appropriate in the course of developing practical skills, for example in collecting and analysing data.

Investigative Skills Assignment (ISA)

The Investigative Skills Assignment carries 38 marks and has two stages.

Stage 1: Collection and Processing of data

Candidates carry out practical work following an AQA task sheet. Centres may use the task sheet as described or may make minor suitable modifi cations to materials or equipment, following AQA guidelines.

Any modifi cations made to the task sheet must be agreed in writing with the AQA Assessment Adviser.

The task may be conducted in a normal timetabled lesson but must be under controlled conditions.

Candidates collect raw data and represent it in a table of their own design or make observations that are recorded on the Candidate Results Sheet. The candidates' work must be handed to the teacher at the end of the session. The teacher assesses the candidates' work following AQA marking guidelines.

There is no specified time limit for this stage.

Stage 2: The ISA written test

The ISA test should be taken as soon as convenient after completion of Stage 1, and under controlled conditions. Each candidate is provided with an ISA test and the candidate's completed material from Stage 1. The teacher uses the AQA marking guidelines to assess the ISA test. The ISA test is in two Sections.

Section A

This consists of a number of questions relating to the candidate's own data.

Section B

At the start of this section, candidates are supplied with additional data on a related topic. A number of questions relating to analysis and evaluation of the data then follow. The number of marks allocated to each section may vary slightly with each ISA test.

Use of ICT during the ISA

ICT may be used during the ISA Stages 1 and 2 but teachers should note any restrictions in the ISA marking guidelines or Teachers Notes. Use of the internet is not permitted.

Candidates absent for the practical work

A candidate absent for the practical work (Stage 1) should be given an opportunity to carry out the practical work before they sit the ISA test. This may be with another group or at a different time. In extreme circumstancs, when such arrangements are not possible, the teacher may supply a candidate with class data. In this case candidates cannot be awarded marks for Stage 1, but can still be awarded marks for Stage 2 of the assessment.

Material from AQA

For each ISA, AQA will provide:

This material must be kept under secure conditions within the centre. If it is to be used in more than one session, then the centre must ensure security of the material between sessions. Further details regarding this material will be provided.

Security of assignments

Completed ISAs should be treated like examination papers and kept under secure conditions until the publication of results.

General Information

Route T Administration

In any year a candidate may attempt either or both of the two ISAs.

For each candidate, the teacher should submit to AQA a total mark comprising:

The ISA component of this mark must come from one ISA only, i.e. the marks awarded for stages of different ISAs cannot be combined.

Candidates may make only one attempt at a particular ISA. Redrafting is not permitted at any stage during the ISA.

The total mark must be submitted to AQA by the due date in the academic year for which the ISA was published.

Work to be submitted

For each candidate in the sample the following materials must be submitted to the moderator by the deadline issued by AQA.

In addition each centre must provide

Working in groups

For the PSA candidates may work in groups provided that any skills being assessed are the work of individual candidates. For the ISA further guidance will be provided in the Teacher Notes.

Other information

Section 6 of this specification outlines further guidance on the supervision and authentication of centre assessed units.

Section 6 also provides information in relation to the internal standardisation of marking for these units.

Please note that the marking of both the PSA and the ISA must be internally standardised as stated in Section 6.4.

Further support

AQA supports the units in a number of ways.

The Assessment Advisers can provide guidance on

Any amendments to the ISA task sheet must be discussed with the Assessment Adviser and confirmation of the amendments made must be submitted to the AQA moderator.

3.8.2 Externally Marked Route X

(PSV/EMPA)

The practical and investigative skills will be assessed through

The PSV requires teachers to verify their candidates' ability to demonstrate safe and skilful practical techniques and make valid and reliable observations.

The EMPA has two stages where candidates

Each stage must be carried out under controlled conditions but may be at a time convenient to the centre. The written test must be completed in a single uninterrupted session.

The EMPA is set and marked by AQA. Only one EMPA at AS and one at A2 will be provided in a given academic year. AQA will stipulate a period of time during which the EMPA (task and written test) must be completed.

Practical Skills verification

Candidates following this route must undertake the practical activities outlined in sections 3.3 for AS or 3.6 for A2 in order to allow candidates suitable opportunities to demonstrate safe and skilful practical techniques and to make reliable and valid observations. The teacher will confirm on the

Candidate Record Form, for each candidate that this requirement has been met. Failure to complete the tick box will lead to a mark of zero being awarded to the candidate for the whole of this unit. Knowledge and understanding of the skills in Section 3.3 and 3.6 will be assessed in Section C of the EMPA written tests.

Tasks are provided in the three areas of chemistry; inorganic, physical and organic chemistry. Candidates should undertake at least two of the task form from each of the three areas of chemistry. In order to provide appropriate opportunities to demonstrate the necessary skills, teachers must not be too prescriptive to the instructions they provide but should allow candidates to make decisions for themselves, particularly concerning the conduct of practical work, their organisation and the manner in which equipment is used.

Candidates should be encouraged to carry out practical and investigative work throughout the course. This work should cover the skills and knowledge of How Science Works (Section 3.7) and in Sections 3.3 and 3.6. Alternative practical activities may be used provided that candidates are given the opportunity to develop the same skills identified in Section 3.3 or 3.6.

Further guidance for conducting practical activities for the PSV will be provided in the Teacher Resource Bank.

ICT

Candidates may use ICT where appropriate in the course of developing practical skills, for example in collecting and analysing data.

Externally Marked Practical Assignment (EMPA)

The Externally Marked Practical Assignment carries 50 marks and has two stages.

Stage 1: Themed task, collection and processing of data

Candidates carry out practical work following an AQA task sheet. The tasks may be conducted in a normal timetabled lesson and at a time convenient to the centre. Candidates collect raw data and represent it in a table of their own design or make observations that are recorded on the Candidate Result Sheet. The candidates' work must be handed to the teacher at the end of each session.

Centres may use the task sheets, as described, or may make minor suitable modifi cations to materials or equipment following AQA guidelines. Any modifi cations made to the task sheet must be agreed in writing with the Assessment Adviser and details must be provided to the AQA Examiner. The task may be conducted in a normal timetabled lesson. There is no specified time limit for this stage.

Stage 2: The EMPA written test

The EMPA test should be taken as soon as convenient after completion of Stage 1 and under controlled conditions. Each candidate is provided with an EMPA test and the candidate's completed material from Stage 1.

The EMPA test is in three Sections.

Section A

Section B

Section C

Use of ICT during the EMPA

ICT may be used during the EMPA Stages 1 and 2 but teachers should note any restrictions in the Teachers' Notes. Use of the internet is not permitted.

Candidates absent for the practical work

A candidate absent for the practical work (Stage 1) should be given an opportunity to carry out the practical work before they sit the EMPA test. This may be with another group or at a different time. In extreme circumstances, when such arrangements are not possible the teacher may supply a candidate with class data. This must be noted on the Candidate Record Form. In this case the candidate cannot be awarded marks for Stage 1, but can still be awarded marks for Stage 2 of the assessment.

Material from AQA

For each EMPA, AQA will provide:

When received, this material must be kept under secure conditions. If it is to be used in more than one session, then the centre must ensure security of material between sessions. Further details regarding this material will be provided.

Security of assignments

Completed EMPAs should be treated like examination papers and kept under secure conditions until sent to the Examiner.

General Information

Route X Administration

Only one EMPA will be available in any year at AS and at A2. AQA will stipulate a period of time during which the EMPA (task and test) must be completed. Candidates may make only one attempt at a particular EMPA and redrafting is not permitted at any stage during the EMPA.

Work to be submitted

The material to be submitted to the examiner for each candidate consists of

In addition each centre must provide

Working in groups

For the PSV candidates may work in groups provided that any skills being assessed are the work of individual candidates. For the EMPA further guidance will be provided but the opportunity for group work will not be a common feature.

Other information

Section 6 of this specification outlines further guidance on the supervision and authentication of Internally assessed units.

Further support

AQA supports centres in a number of ways.

Adviser and confirmation of the amendments made must be submitted to the AQA Examiner.

3.8.3 General Marking Guidance for each PSA

Centres should bear in mind that satisfactory completion of a PSA task by the candidate should be judged in the context of an ability to work safely and in an organised manner, when demonstrating appropriate manipulative skills. Each task should be graded on a three point scale (0, 1 or 2 marks) with the following general guidelines for the award of each point on the scale.

Further support

AQA supports the centre assessed units in a number of ways.

3.8.4 General Marking Guidance for each PSA

Centres should bear in mind that satisfactory completion of a PSA task by the candidate should be judged in the context of an ability to work safely and in an organised manner, when demonstrating appropriate manipulative skills.

Each task should be graded on a three point scale (0, 1 or 2 marks) with the following general guidelines for the award of each point on the scale.

Assessment Descriptors

2 marks

Candidates are able to follow a set of instructions for the task in a safe and organised way. Measurements are precise and within the expected range. Candidates require minimal additional guidance to carry out the task in a competent manner and are able to produce an outcome which is within the expected tolerance for the activity or produce a set of results, most of which are correct.

1 mark Candidates are able to follow a set of instructions for the task in a reasonably safe way, but could be better organised. Measurements are imprecise or outside the expected range. Candidates require some additional guidance to carry out the task to a standard which is considered appropriate and produce an outcome, which, whilst acceptable, may not be within the expected tolerance for the activity or produce a set of results, only some of which are correct.

0 marks

Candidates have significant difficulty in following a set of instructions for the task and their work is poorly organised or unsafe. Measurements are imprecise or outside the expected range. Candidates require significant additional guidance to carry out the task to a standard which is considered appropriate and produce an outcome which is significantly outside the expected tolerance for the activity or produce a set of results, few of which are correct.

The following sections detail, for AS and A2, possible contexts and marking guidance for each area of chemistry.

Practical Skills Assessment: AS Inorganic Chemistry

Task and possible context Specific marking guidance

Make up a volumetric solution

For example: The preparation of a standard solution of sodium carbonate

2 marks: All areas of the task are carried out competently. The weighing is precise and within the required range. The transfer of solid to a graduated flask is done with care. The solution is made up to the mark, accurately.

1 mark: One of the areas of the task is performed poorly. The weighing is imprecise or outside the required range OR The transfer of solid to the graduated flask is careless OR The solution is made up inaccurately. (e.g. the flask is over-filled)

0 marks: At least two of the areas of the task are performed poorly. The weighing is imprecise or outside the required range. The transfer of solid to the graduated flask is careless. The solution is made up inaccurately.

Carry out a simple acid-base titration

For example: Determine the concentration of unknown hydrochloric acid by titration

2 marks: All areas of the task are carried out competently. The burette is filled safely with the correct reagent (including below the tap). The pipette and filler, burette and conical flask are all used correctly. The titration results are concordant and the average titre is judged accurate.

1 mark: One of the areas of the task is performed poorly. The burette is filled with the incorrect reagent or the funnel is left in or the burette is not filled below the tap OR One of either, the pipette, pipette filler, burette or conical flask is not used correctly OR The titration results are not concordant or the average titre is inaccurate.

0 marks: At least two of the areas of the task are performed poorly. The burette is filled with the incorrect reagent or the funnel is left in or the burette is not filled below the tap. One of either, the pipette, pipette filler, burette or conical flask is not used correctly. The titration results are not concordant or the average titre is inaccurate.

Carry out some inorganic tests

For example: Tests for anions

2 marks: All areas of the task are carried out competently. The quantities of reagents are appropriate. The tests (heating, shaking etc.) are carried out safely and with due care. Most of the observations are correct.

1 mark: One of the areas of the task is performed poorly. The quantities of reagents are inappropriate OR The tests (heating, shaking etc.) are carried out in a careless manner OR Only some of the observations are correct.

0 marks: At least two of the areas of the task are performed poorly. The quantities of reagents are inappropriate. The tests (addition, heating, shaking etc.) are carried out in a careless manner. Few of the observations are correct.

Practical Skills Assessment: AS Physical Chemistry

Task and possible context Specific marking guidance

Measure an enthalpy change

For example: Use Hess's law to find anunknown enthalpy change, such as the reaction of anhydrous copper(II) sulfate with water to produce hydrated crystals

2 marks: All areas of the task are carried out competently. Masses and volumes are measured precisely and within the required range. Initial/final temperatures are measured precisely and mixing is complete. The results lead to an enthalpy change which is within the expected range.

1 mark: One of the areas of the task is performed poorly. Masses or volumes are measured imprecisely or not in the required range OR Temperatures are measured imprecisely or mixing is incomplete OR The results lead to an enthalpy change which is outside the expected range.

0 marks: At least two of the areas of the task are performed poorly. Masses or volumes are measured imprecisely or not in the required range. Temperatures are measured imprecisely or mixing is incomplete. The results lead to an enthalpy change which is outside the expected range.

Determine the Mr of a volatile liquid or the Mr of a gas

For example: Determine the Mr of hexane or the Mr of carbon dioxide

2 marks: All areas of the task are carried out competently. The apparatus is weighed precisely and handled carefully. The transfer of liquid or gas is carried out safely and with due care. The apparatus is equilibrated and all necessary measurements taken.

1 mark: One of the areas of the task is performed poorly. The apparatus is weighed imprecisely or handled without due care OR The transfer of liquid or gas is not carried out safely or with due care OR The apparatus has not equilibrated or some measurements are not taken.

0 marks: At least two of the areas of the task are performed poorly. The apparatus is weighed imprecisely or handled without due care. The transfer of liquid or gas is not carried out safely or with due care. The apparatus has not equilibrated or some measurements are not taken.

Investigate how the rate of a reaction changes with temperature

For example: Investigate the rate of reaction of sodium thiosulfate with acid at different temperatures

2 marks: All areas of the task are carried out competently. The quantities of reagents are appropriate and the apparatus is safe. Heating is carried out with due care and only as long as necessary. The change in the measured rate is within the expected range.

1 mark: One of the areas of the task is performed poorly. The quantities of reagents are inappropriate or the apparatus is unsafe OR Heating is carried out with insufficient care or longer than necessary OR The change in the measured rate is not within the expected range.

0 marks: At least two of the areas of the task are performed poorly. The quantities of reagents are inappropriate or the apparatus is unsafe. Heating is carried out with insufficient care or longer than necessary. The change in the measured rate is not within the expected range

Practical Skills Assessment: AS Organic Chemistry

Task and possible context Specific marking guidance

Distil a product from a reaction

For example: The preparation of ethanal from the oxidation of ethanol or the preparation of cyclohexene from cyclohexanol

2 marks: All areas of the task are carried out competently. The apparatus set-up is safe and appropriate. Heating is carried out with due care and only as long as necessary. The yield of product is appropriate.

1 mark: One of the areas of the task is performed poorly. The apparatus set-up is inappropriate OR Heating is carried out with inSufficient care or longer than necessary OR The yield of product is inappropriate.

0 marks: At least two of the areas of the task are performed poorly. The apparatus set-up is inappropriate. Heating is carried out with inSufficient care or longer than necessary. The yield of product is inappropriate.

Carry out some organic tests

For example: Tests for alkene, alcohol, acid, aldehyde

2 marks: All areas of the task are carried out competently. The quantities of reagents are appropriate. The tests (heating, shaking etc.) are carried out safely and with due care. Nearly all of the observations are correct.

1 mark: One of the areas of the task is performed poorly. The quantities of reagents are inappropriate OR The tests (heating, shaking etc.) are carried out in a careless manner OR Only some of the observations are correct.

0 marks: At least two of the areas of the task are performed poorly.

The quantities of reagents are inappropriate. The tests (addition, heating, shaking etc.) are carried out in a careless manner. Few of the observations are correct.

Investigate the combustion of alcohols

For example: Use a calorimetric method to measure the enthalpies of combustion in an homologous series

2 marks: All areas of the task are carried out competently. Masses and volumes are measured precisely and within the required range. Initial/final temperatures are measured precisely. The range and trend in enthalpies is as expected for the series.

1 mark: One of the areas of the task is performed poorly. Masses or volumes are measured imprecisely or not in the required range OR Temperatures are measured imprecisely OR The range or trend in enthalpies is not as expected for the series.

0 marks: At least two of the areas of the task are performed poorly. Masses or volumes are measured imprecisely or not in the required range. Temperatures are measured imprecisely. The range or trend in enthalpies is not as expected for the series.

Practical Skills Assessment: A2 Inorganic Chemistry

Task and possible context Specific marking guidance

Carry out a redox titration

For example: The analysis of iron tablets by titration using acidified potassium manganate(VII)

2 marks: All areas of the task are carried out competently. The burette is filled safely with the correct reagent (including below the tap) The pipette and filler, burette and conical flask are all used correctly. The titration results are concordant and the average titre is accurate.

1 mark: One of the areas of the task is performed poorly. The burette is filled with the incorrect reagent or the funnel is left in or the burette is not filled below the tap OR One of either the pipette, pipette filler, burette or conical flask is used incorrectly OR The titration results are not concordant or the average titre is inaccurate.

0 marks: At least two of the areas of the task are performed poorly. The burette is filled with the incorrect reagent or the funnel is left in or the burette is not filled below the tap. One of either the pipette, filler, burette or conical flask is used incorrectly. The titration results are not concordant or the average titre is inaccurate.

Investigate the chemistry of transition metal compounds in a series of experiments

For example: The chemistry of copper compounds

2 marks: All experiments are carried out competently. The quantities of reagents are appropriate. All experiments are carried out safely and with due care. Nearly all of the observations are correct.

1 mark: One of the areas of the task is performed poorly. The quantities of reagents are inappropriate OR Some of the experiments are carried out in a careless manner OR Only some of the observations are correct.

0 marks: At least two of the areas of the task are performed poorly. The quantities of reagents are inappropriate. Many of the experiments are carried out in a careless manner. Few of the observations are correct.

Prepare an inorganic complex

For example: The preparation of hexaamminecobalt(III) chloride

2 marks: All areas of the task are carried out competently. The quantities of reagents are appropriate for the preparation. The apparatus set-up for the preparation is safe and appropriate. The experiment is carried out safely and produces an appropriate quantity and quality of product.

1 mark: One of the areas of the task is performed poorly. The quantities of reagents are inappropriate for the preparation OR The apparatus set-up for each experiment is unsafe or inappropriate OR The experiments are carried out with inSufficient care or the yield is poor.

0 marks: At least two of the areas of the task are performed poorly. The quantities of reagents are inappropriate for the preparation. The apparatus set-up for each experiment is unsafe or inappropriate. The experiments are carried out with inSufficient care or the yield is poor.

Practical Skills Assessment: A2 Physical Chemistry

Task and possible context Specific marking guidance

Carry out a kinetic study to determine the order of a reaction

For example: An iodine clock experiment e.g. the reaction of sulfite ions with iodate(V) ions

2 marks: All areas of the task are carried out competently. The quantities of reagents are measured precisely. Times are measured accurately and recorded precisely. Sufficient values are on a good straight line and the order of reaction is in the expected range.

1 mark: One of the areas of the task is performed poorly. The quantities of reagents are measured imprecisely ORTimes are measured inaccurately or recorded imprecisely OR The values are scattered or the order is not in the expected range.

0 marks: At least two of the areas of the task are performed poorly.The quantities of reagents are measured imprecisely. Times are measured inaccurately or recorded imprecisely. The values are scattered or the order is not in the expected range.

Determine an equilibrium constant

For example: Determine a value of Kc for the reaction of ethanol with ethanoic acid

2 marks: All areas of the task are carried out competently. The quantities of reagents are measured precisely. The titrations are carried out with due care and data recorded precisely. The value of the equilibrium constant is in the expected range.

1 mark: One of the areas of the task is performed poorly. The quantities of reagents are measured imprecisely OR Titrations are carried out with inSufficient care or data recorded imprecisely OR The value of the equilibrium constant is not in the expected range.

0 marks: At least two of the areas of the task are performed poorly. The quantities of reagents are measured imprecisely. Titrations are carried out with insufficient care or data recorded imprecisely.

The value of the equilibrium constant is not in the expected range.

Investigate how pH changes when a weak acid reacts with a strong base or when a strong acid reacts with a weak base

For example: Determine the pH curve for ethanoic acid reacting with sodium hydroxide

2 marks: All areas of the task are carried out competently. The apparatus is used correctly. The pH values are recorded correctly. The pH changes are in the expected range.

1 mark: One of the areas of the task is performed poorly. The apparatus is used incorrectly OR The pH values are recorded incorrectly OR The pH changes are not in the expected range.

0 marks: At least two of the areas of the task are performed poorly. The apparatus is used incorrectly. The pH values are recorded incorrectly. The pH changes are not in the expected range.

Practical Skills Assessment: A2 Organic Chemistry

Task and possible context Specific marking guidance

Prepare a solid organic compound

For example: The preparation of aspirin

2 marks: All areas of the task are carried out competently. The quantities of reagents are appropriate for the preparation. The apparatus set-up for the preparation is safe and appropriate. The experiment is carried out safely and produces an appropriate quantity and quality of product.

1 mark: One of the areas of the task is performed poorly. The quantities of reagents are inappropriate for the preparation OR The apparatus set-up for each experiment is unsafe or inappropriate OR The experiment is carried out with inSufficient care or the yield is poor.

0 marks: At least two of the areas of the task are performed poorly. The quantities of reagents are inappropriate for the preparation. The apparatus set-up for each experiment is unsafe or inappropriate. The experiment is carried out with inSufficient care or the yield is poor.

Purify an organic solid

For example: The recrystallisation of impure benzenecarboxylic acid from hot water

2 marks: All areas of the task are carried out competently. The quantity of solvent is appropriate. The recrystallisation process is carried out safely and with due care. The quantity and quality of recrystallised product are both appropriate.

1 mark: One of the areas of the task is performed poorly. The quantity of solvent is inappropriate OR The recrystallisation process is carried out with insufficient care OR Either the quantity or quality of recrystallised product is inappropriate.

0 marks: At least two of the areas of the task are performed poorly. The quantity of solvent is inappropriate. The recrystallisation process is carried out with insufficient care. Either the quantity or quality of recrystallised product is inappropriate

Test the purity of an organic solid

For example: Determine the melting point of benzenecarboxylic acid

2 marks: All areas of the task are carried out competently. The quantity used and the preparation of the solid are appropriate (e.g. dry, powder). The apparatus set-up is safe and appropriate. Heating is carried out with due care and only as long as necessary, giving an accurate value for the melting point.

1 mark: One of the areas of the task is performed poorly. Either the quantity used or the preparation of the solid is inappropriate OR The apparatus set-up is unsafe or inappropriate OR Heating is longer than necessary and the m.p. is inaccurate.

0 marks: At least two of the areas of the task are performed poorly. Either the quantity used or the preparation of the solid is inappropriate. The apparatus set-up is unsafe or inappropriate. Heating is longer than necessary and the m.p. is inaccurate.