Practical Assessment - A-Levels Chemistry
7 AS practical assessment
Practical work is at the heart of chemistry, so we have placed it at the heart of this specification.
Assessment of practical skills in this AS specification will be by written exams only.
The practical endorsement does not apply to the AS specification. A rich diet of practical work is essential to develop students’ manipulative skills and understanding of the processes of scientific investigation. It also contributes to teaching and learning of the concepts within this specification.
Questions in the papers have been written in the expectation that students have carried out at least the 6 required practical activities in section 7.2.
15% of the marks in the papers will relate to practical work.
7.1 Use of apparatus and techniques
All students taking this specification are expected to have carried out the required practical activities in section 7.2. These develop skills in the use of many of the following apparatus and techniques. This list is a compulsory element of the full A-level course. It is introduced here for reference and to aid co-teaching the AS and A-level specifications.
| Apparatus and techniques | |
|---|---|
| AT a | Use appropriate apparatus to record a range of measurements (to include mass, time, volume of liquids and gases, temperature) |
| AT b | Use water bath or electric heater or sand bath for heating |
| AT c | Measure pH using pH charts, or pH meter, or pH probe on a data logger |
| AT d | Use laboratory apparatus for a variety of experimental techniques including: • titration, using burette and pipette • distillation and heating under reflux, including setting up glassware using retort stand and clamps • qualitative tests for ions and organic functional groups • filtration, including use of fluted filter paper, or filtration under reduced pressure |
| AT e | Use volumetric flask, including accurate technique for making up a standard solution |
| AT f | Use acid–base indicators in titrations of weak/strong acids with weak/strong alkalis |
| AT g | Purify: • a solid product by recrystallisation • a liquid product, including use of separating funnel |
| AT h | Use melting point apparatus |
| AT i | Use thin-layer or paper chromatography |
| AT j | Set up electrochemical cells and measuring voltages |
| AT k | Safely and carefully handle solids and liquids, including corrosive, irritant, flammable and toxic substances |
| AT l | Measure rates of reaction by at least two different methods, for example: • an initial rate method such as a clock reaction • a continuous monitoring method |
7.2 Required practical activities
The following practicals must be carried out by all students taking this course. Written papers will assess knowledge and understanding of these, and the skills exemplified within each practical.
| Required activity | Apparatus and technique reference |
|---|---|
| 1 Make up a volumetric solution and carry out a simple acid–base titration | a, d, e, f, k |
| 2 Measurement of an enthalpy change | a, d, k |
| 3 Investigation of how the rate of a reaction changes with temperature | a, b, k |
| 4 Carry out simple test-tube reactions to identify: • cations – Group 2, NH4+ • anions – Group 7 (halide ions), OH−, CO32−, SO42− | d, k |
| 5 Distillation of a product from a reaction | b, d, k |
| 6 Tests for alcohol, aldehyde, alkene and carboxylic acid | b, d, k |
Teachers are encouraged to vary their approach to these practical activities. Some are more suitable for highly structured approaches that develop key techniques. Others allow opportunities for students to develop investigative approaches. This list is not designed to limit the practical activities carried out by students. A rich practical experience for students will include more than the 6 required practical activities. The explicit teaching of practical skills will build students’ competence. Many teachers will also use practical approaches to the introduction of content knowledge in the course of their normal teaching.
7.3 Practical skills to be assessed in written papers
Overall, at least 15% of the marks for all AS Chemistry courses will require the assessment of practical skills.
In order to be able to answer these questions, students need to have been taught, and to have acquired competence in, the appropriate areas of practical skills as indicated in the tables of coverage below.
7.3.1 Independent thinking
| Practical skill | |
|---|---|
| PS 1.1 | Solve problems set in practical contexts |
| PS 1.2 | Apply scientific knowledge to practical contexts |
7.3.2 Use and application of scientific methods and practices
| Practical skill | |
|---|---|
| PS 2.1 | Comment on experimental design and evaluate scientific methods |
| PS 2.2 | Present data in appropriate ways |
| PS 2.3 | Evaluate results and draw conclusions with reference to measurement uncertainties and errors |
| PS 2.4 | Identify variables including those that must be controlled |
7.3.3 Numeracy and the application of mathematical concepts in a practical context
| Practical skill | |
|---|---|
| PS 3.1 | Plot and interpret graphs |
| PS 3.2 | Process and analyse data using appropriate mathematical skills as exemplified in the mathematical appendix for each science |
| PS 3.3 | Consider margins of error, accuracy and precision of data |
7.3.4 Instruments and equipment
| Practical skill | |
|---|---|
| PS 4.1 | Know and understand how to use a wide range of experimental and practical instruments, equipment and techniques appropriate to the knowledge and understanding included in the specification |
8 A-level practical assessment
Practical work is at the heart of chemistry, so we have placed it at the heart of this specification.
Practical assessments have been divided into those that can be assessed in written exams and those that can only be directly assessed whilst students are carrying out experiments.
A-level grades will be based only on marks from written exams.
A separate endorsement of practical skills will be taken alongside the A-level. This will be assessed by teachers and will be based on direct observation of students’ competency in a range of skills that are not assessable in written exams.
8.1 Use of apparatus and techniques
All students taking an A-level Chemistry qualification are expected to have had opportunities to use the following apparatus and develop and demonstrate these techniques. These apparatus and techniques are common to all A-level Chemistry specifications.
Carrying out the 12 required practicals in section 8.2 means that students will have experienced use of each of these apparatus and techniques. However, teachers are encouraged to develop students’ abilities by inclusion of other opportunities for skills development, as exemplified in the right-hand column of the content section of this specification.
| Apparatus and techniques | |
|---|---|
| AT a | Use appropriate apparatus to record a range of measurements (to include mass, time, volume of liquids and gases, temperature) |
| AT b | Use water bath or electric heater or sand bath for heating |
| AT c | Measure pH using pH charts, or pH meter, or pH probe on a data logger |
| AT d | Use laboratory apparatus for a variety of experimental techniques including: • titration, using burette and pipette • distillation and heating under reflux, including setting up glassware using retort stand and clamps • qualitative tests for ions and organic functional groups • filtration, including use of fluted filter paper, or filtration under reduced pressure |
| AT e | Use volumetric flask, including accurate technique for making up a standard solution |
| AT f | Use acid–base indicators in titrations of weak/strong acids with weak/strong alkalis |
| AT g | Purify: • a solid product by recrystallisation • a liquid product, including use of separating funnel |
| AT h | Use melting point apparatus |
| AT i | Use thin-layer or paper chromatography |
| AT j | Set up electrochemical cells and measuring voltages |
| AT k | Safely and carefully handle solids and liquids, including corrosive, irritant, flammable and toxic substances |
| AT l | Measure rates of reaction by at least two different methods, for example: • an initial rate method such as a clock reaction • a continuous monitoring method |
8.2 Required practical activities
The following practicals must be carried out by all students taking this course. Written papers will assess knowledge and understanding of these, and the skills exemplified within each practical.
| Required activity | Apparatus and technique reference |
|---|---|
| 1 Make up a volumetric solution and carry out a simple acid–base titration | a, d, e, f, k |
| 2 Measurement of an enthalpy change | a, d, k |
| 3 Investigation of how the rate of a reaction changes with temperature | a, b, k |
| 4 Carry out simple test-tube reactions to identify: • cations – Group 2, NH4+ • anions – Group 7 (halide ions), OH−, CO32−, SO42− | d, k |
| 5 Distillation of a product from a reaction | b, d, k |
| 6 Tests for alcohol, aldehyde, alkene and carboxylic acid | b, d, k |
| 7 Measuring the rate of reaction: • by an initial rate method • by a continuous monitoring method | a, k, l a, k, l |
| 8 Measuring the EMF of an electrochemical cell | j, k |
| 9 Investigate how pH changes when a weak acid reacts with a strong base and when a strong acid reacts with a weak base | a, c, d, k |
| 10 Preparation of: • a pure organic solid and test of its purity • a pure organic liquid | a, b, d, g, h, k b, d, g, k |
| 11 Carry out simple test-tube reactions to identify transition metal ions in aqueous solution | b, d, k |
| 12 Separation of species by thin-layer chromatography | i, k |
Teachers are encouraged to vary their approach to these practical activities. Some are more suitable for highly structured approaches that develop key techniques. Others allow opportunities for students to develop investigative approaches. This list is not designed to limit the practical activities carried out by students. A rich practical experience for students will include more than the 12 required practical activities. The explicit teaching of practical skills will build students’ competence. Many teachers will also use practical approaches to the introduction of content knowledge in the course of their normal teaching. Students’ work in these activities can also contribute towards the endorsement of practical skills.
8.3 Practical skills to be assessed in written papers
Overall, at least 15% of the marks for all A-level Chemistry courses will require the assessment of practical skills.
In order to be able to answer these questions, students need to have been taught, and to have acquired competence in, the appropriate areas of practical skills as indicated in the tables of coverage below.
8.3.1 Independent thinking
| Practical skill | |
|---|---|
| PS 1.1 | Solve problems set in practical contexts |
| PS 1.2 | Apply scientific knowledge to practical contexts |
8.3.2 Use and application of scientific methods and practices
| Practical skill | |
|---|---|
| PS 2.1 | Comment on experimental design and evaluate scientific methods |
| PS 2.2 | Present data in appropriate ways |
| PS 2.3 | Evaluate results and draw conclusions with reference to measurement uncertainties and errors |
| PS 2.4 | Identify variables including those that must be controlled |
8.3.3 Numeracy and the application of mathematical concepts in a practical context
| Practical skill | |
|---|---|
| PS 3.1 | Plot and interpret graphs |
| PS 3.2 | Process and analyse data using appropriate mathematical skills as exemplified in the mathematical appendix for each science |
| PS 3.3 | Consider margins of error, accuracy and precision of data |
8.3.4 Instruments and equipment
| Practical skill | |
|---|---|
| PS 4.1 | Know and understand how to use a wide range of experimental and practical instruments, equipment and techniques appropriate to the knowledge and understanding included in the specification |
8.4 Practical skills to be assessed via endorsement
8.4.1 Cross-board statement on practical endorsement
The assessment of practical skills is a compulsory requirement of the course of study for A-level qualifications in biology, chemistry and physics. It will appear on all students’ certificates as a separately reported result, alongside the overall grade for the qualification. The arrangements for the assessment of practical skills will be common to all awarding organisations.
These arrangements will include:
- A minimum of 12 practical activities to be carried out by each student which, together, meet the requirements of Appendices 5b (Practical skills identified for direct assessment and developed through teaching and learning) and 5c (Use of apparatus and techniques) from the prescribed subject content, published by the Department for Education (DfE). The required practical activities will be defined by each awarding organisation.
- Teachers will assess students against Common Practical Assessment Criteria (CPAC) issued jointly by the awarding organisations. The CPAC below are based on the requirements of Appendices 5b and 5c of the subject content requirements published by the DfE, and define the minimum standard required for the achievement of a pass.
- Each student will keep an appropriate record of their practical work, including their assessed practical activities.
- Students who demonstrate the required standard across all the requirements of the CPAC will receive a ‘pass’ grade.
- There will be no separate assessment of practical skills for AS qualifications.
- Students will answer questions in the AS and A-level exam papers that assess the requirements of Appendix 5a (Practical skills identified for indirect assessment and developed through teaching and learning) from the prescribed subject content, published by the DfE. These questions may draw on, or range beyond, the practical activities included in the specification.
8.4.2 Criteria for the assessment of practical competency in A-level Biology, Chemistry and Physics
| Competency | Practical mastery |
|---|---|
| In order to be awarded a Pass a student must, by the end of the practical science assessment, consistently and routinely meet the criteria in respect of each competency listed below. A student may demonstrate the competencies in any practical activity undertaken as part of that assessment throughout the course of study. Students may undertake practical activities in groups. However, the evidence generated by each student must demonstrate that they independently meet the criteria outlined below in respect of each competency. Such evidence: • (a) will comprise both the student’s performance during each practical activity and his or her contemporaneous record of the work that he or she has undertaken during that activity, and • (b) must include evidence of independent application of investigative approaches and methods to practical work. | |
| 1. Follows written procedures | (a) Correctly follows written instructions to carry out experimental techniques or procedures. |
| 2. Applies investigative approaches and methods when using instruments and equipment | (a) Correctly uses appropriate instrumentation, apparatus and materials (including ICT) to carry out investigative activities, experimental techniques and procedures with minimal assistance or prompting. (b) Carries out techniques or procedures methodically, in sequence and in combination, identifying practical issues and making adjustments where necessary. (c) Identifies and controls significant quantitative variables where applicable, and plans approaches to take account of variables that cannot readily be controlled. (d) Selects appropriate equipment and measurement strategies in order to ensure suitably accurate results. |
| 3. Safely uses a range of practical equipment and materials | (a) Identifies hazards and assesses risks associated with those hazards, making safety adjustments as necessary, when carrying out experimental techniques and procedures in the lab or field. (b) Uses appropriate safety equipment and approaches to minimise risks with minimal prompting. |
| 4. Makes and records observations | (a) Makes accurate observations relevant to the experimental or investigative procedure. (b) Obtains accurate, precise and sufficient data for experimental and investigative procedures and records this methodically using appropriate units and conventions. |
| 5. Researches, references and reports | (a) Uses appropriate software and/or tools to process data, carry out research and report findings. (b) Cites sources of information demonstrating that research has taken place, supporting planning and conclusions. |