Practical skills
Required Practicals Revision
Know the method, variables, hazards, and evaluation for every practical
Why This Matters
the exam board has 21 required practicals across Biology, Chemistry, and Physics (8 Biology, 8 Chemistry, 10 Physics for Separate Sciences; fewer for Combined). Questions about required practicals appear on every paper and can account for 15% of the total marks. You don’t repeat the experiments in the exam — but you must know the method, the variables, the equipment, the hazards, how to improve accuracy, and how to evaluate the results. These are some of the most predictable marks on the paper if you revise them properly.
Step-by-Step Method
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1
List all required practicals — Use the specification to create a checklist of every required practical for your course. Tick each one off as you revise it. Don’t rely on memory — use the spec.
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2
For each practical, write a summary covering — (a) Aim: what the practical tests; (b) Method: step-by-step procedure; (c) Variables: independent, dependent, and control variables; (d) Equipment: key apparatus including resolution; (e) Hazards and precautions; (f) Expected results and how to process data; (g) How to improve accuracy and reliability.
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3
Draw the set-up from memory — Many practicals require a labelled diagram in the exam. Practise drawing the apparatus set-up with labels until you can do it quickly and accurately.
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4
Answer past paper practical questions — AQA reuses practical contexts. Practise questions from past papers that are based on required practicals — you’ll see the same practical tested in different ways.
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5
Learn the key vocabulary — Examiners expect precise terminology: “reproducible” (different people get the same results), “repeatable” (same person gets same results), “resolution” (smallest interval on a measuring instrument), “anomalous” (a result that doesn’t fit the pattern).
When and How Often
Cover 2–3 practicals per revision session (30 minutes). Cycle through all 21 over 2–3 weeks, then review the ones you found hardest.
Biology
- Microscopy — using a light microscope to observe cells
- Microbiology — effect of antiseptics/antibiotics on bacterial growth
- Osmosis — effect of sugar solutions on plant tissue
- Food tests — testing for starch, glucose, protein, and lipids
- Enzymes — effect of pH on enzyme activity (amylase)
- Photosynthesis — effect of light intensity on rate of photosynthesis
- Reaction time — measuring the effect of a factor on reaction time
- Plant responses — effect of light or gravity on seedling growth
Chemistry
- Making salts — preparation of a pure, dry sample of a soluble salt
- Electrolysis — electrolysis of aqueous solutions
- Temperature changes — investigating exothermic and endothermic reactions
- Rates of reaction — effect of concentration on rate (e.g. sodium thiosulfate)
- Chromatography — separating and identifying substances using paper chromatography
- Water purification — analysis and purification of water samples
- Identifying ions — flame tests and chemical tests for ions
- Titration — finding the concentration of an acid or alkali (Higher/Separate only)
Physics
- Specific heat capacity — measuring the specific heat capacity of a material
- Thermal insulation — investigating the effectiveness of different materials
- Resistance — investigating factors affecting resistance of a wire
- I-V characteristics — for a filament lamp, diode, and fixed resistor
- Density — measuring the density of regular and irregular objects
- Force and extension — investigating Hooke’s law
- Acceleration — investigating the effect of force on acceleration
- Waves — measuring the frequency, wavelength, and speed of waves in a ripple tank
- Light — investigating reflection and refraction of light
- Radiation — investigating how the amount of infrared radiation absorbed/emitted depends on surface colour
| Component | Detail |
|---|---|
| Aim | Investigate the effect of sugar solution concentration on the mass of potato cylinders |
| Independent variable | Concentration of sugar solution (e.g. 0.0, 0.2, 0.4, 0.6, 0.8, 1.0 mol/dm³) |
| Dependent variable | Change in mass of potato cylinder |
| Control variables | Volume of solution, size/type of potato cylinder, temperature, time left in solution |
| Equipment | Potato, cork borer, balance (0.01 g), boiling tubes, sugar solutions, ruler |
| Hazard | Sharp cork borer — cut away from body on a cutting board |
| Expected results | In dilute solutions: potato gains mass (water enters by osmosis). In concentrated solutions: potato loses mass (water leaves by osmosis). At the isotonic point: no change. |
| Improving accuracy | Repeat 3 times per concentration and calculate mean. Blot potato dry before weighing. Use same potato for consistency. |
Common Mistakes
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Confusing independent and dependent variables — The independent variable is what you change; the dependent variable is what you measure. Get these the wrong way round and you lose marks on the very first line.
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Forgetting control variables — Every practical has variables that must be kept the same for a fair test. “To make it a fair test” is not enough — you must name the specific variables you controlled.
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Not mentioning repeats — “Repeat 3 times and calculate the mean” is expected in almost every practical method. It improves reliability and helps identify anomalies.