If you're sitting AQA Combined Science: Trilogy (spec code 8464), there are 21 required practicals you need to know across Biology, Chemistry and Physics. The spec numbers them 1 to 21 in one continuous run: Biology takes practicals 1 to 7, Chemistry 8 to 13, and Physics 14 to 21. You won't carry any of them out in the exam, but questions about method, variables, results and conclusions turn up on every one of the six papers. For OCR, we have separate guides for Gateway (spec A) and Twenty First Century (spec B).
This guide walks through all 21 practicals in AQA's numbering, flags which paper each sits under, and reconciles exactly which practicals get dropped if you're on Trilogy rather than the Triple separate sciences. Different boards use different language for the same thing: AQA says "required practicals", Edexcel says "core practicals", OCR says "PAGs" (Practical Activity Groups). This article is AQA Trilogy only. If you're on Edexcel 1SC0, use our Edexcel Combined Science core practicals guide instead.
This article was last checked against the AQA Combined Science: Trilogy (8464) specification on **14 October 2026**. Specifications and assessment detail change often, so cross-check the current AQA specification page before relying on any specific detail.
Trilogy is the double-award version of AQA GCSE Science. You come out with two grades (from 9-9 down to 1-1) on one certificate. If you're on the Triple route, you sit three separate GCSEs with 28 required practicals in total: 10 Biology, 8 Chemistry, 10 Physics. The maths is in the Combined vs Triple reconciliation section below.
All 21 AQA Trilogy required practicals
The table below lists every required practical on AQA 8464, in the specification's own 1 to 21 numbering. Each one is tied to a topic area, and exam questions will usually appear within that topic's section of the paper. Papers are 1 hour 15 minutes long, 70 marks each, and each paper accounts for 16.7% of the overall grade.
| No. | Required practical | Science | Paper |
|---|---|---|---|
| 1 | Microscopy: observe, draw and label plant or animal cells with a scale | Biology | 1 |
| 2 | Osmosis: effect of sugar or salt solutions on plant tissue mass | Biology | 1 |
| 3 | Food tests: Benedict's, iodine, Biuret and the ethanol emulsion test | Biology | 1 |
| 4 | Enzymes: effect of pH on amylase activity | Biology | 1 |
| 5 | Photosynthesis: effect of light intensity on the rate of photosynthesis | Biology | 1 |
| 6 | Reaction time: effect of a factor on human reaction time | Biology | 2 |
| 7 | Field investigations: measuring population size using sampling | Biology | 2 |
| 8 | Making salts: pure, dry sample of a soluble salt from an insoluble oxide or carbonate | Chemistry | 1 |
| 9 | Electrolysis of aqueous solutions using inert electrodes | Chemistry | 1 |
| 10 | Temperature changes: variables affecting energy change in reacting solutions | Chemistry | 1 |
| 11 | Rates of reaction: effect of concentration on rate (gas volume or turbidity) | Chemistry | 2 |
| 12 | Chromatography: separating mixtures and calculating R<sub>f</sub> values | Chemistry | 2 |
| 13 | Water analysis: pH, dissolved solids and distillation of water samples | Chemistry | 2 |
| 14 | Specific heat capacity of one or more materials | Physics | 1 |
| 15 | Resistance: factors affecting the resistance of electrical circuits | Physics | 1 |
| 16 | I–V characteristics: filament lamp, diode and a resistor at constant temperature | Physics | 1 |
| 17 | Density: densities of regular and irregular solids and of liquids | Physics | 1 |
| 18 | Force and extension of a spring | Physics | 2 |
| 19 | Acceleration: force vs acceleration and mass vs acceleration | Physics | 2 |
| 20 | Waves: frequency, wavelength and speed in a ripple tank and in a solid | Physics | 2 |
| 21 | Infrared: absorption and emission by different surfaces | Physics | 2 |
A few patterns worth noticing. Biology Papers 1 and 2 split the practicals cleanly: practicals 1 to 5 sit on Paper 1 (Cell biology, Organisation, Infection and response, Bioenergetics), and 6 and 7 sit on Paper 2 (Homeostasis and response; Inheritance, variation and evolution; Ecology). Chemistry Paper 1 covers practicals 8 to 10 (Atomic structure, Bonding, Quantitative chemistry, Chemical changes, Energy changes), while Paper 2 covers 11 to 13 (Rates and extent, Organic, Chemical analysis, Earth atmosphere, Using resources). Physics Paper 1 covers 14 to 17 (Energy, Electricity, Particle model, Atomic structure), and Paper 2 covers 18 to 21 (Forces, Waves, Magnetism and electromagnetism).
How practical skills are assessed
There's no separate practical exam for AQA Combined Science. Instead, AQA weaves practical-skills questions through all six written papers. Across the full qualification, 20% of marks sit under AO3 (analyse information and ideas; evaluate; develop and improve experimental procedures), and AQA writes at least 15% of marks across the papers so that they specifically assess practical skills. In practice that means a handful of questions on every paper that look like method descriptions, variable identification, data analysis or evaluation of an unfamiliar experiment.
The four questions AQA keeps coming back to for every required practical are the same ones:
- Describe the method. List the steps in order, name the equipment, state the quantities. Vague answers like "test it with a chemical" score zero.
- Identify the variables. Name the independent variable (what you change), the dependent variable (what you measure), and at least two control variables. Say how you'd control each one.
- Explain the results. Use scientific knowledge to say why the data came out that way. For example, a potato gaining mass in a dilute sugar solution because water moved in by osmosis, from higher water potential to lower water potential.
- Evaluate the method. Spot weaknesses and suggest improvements. The usual trio: more precise equipment (accuracy), more repeats with a mean (reliability), better control of a variable (validity).
Six-mark extended-response questions sometimes focus entirely on one required practical. Those need a logical structure: method, science, link to the context.
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Combined vs Triple reconciliation
This is the single thing students get wrong when they revise from a Triple-focused resource. Trilogy drops seven practicals that are present on the three separate GCSEs. Triple totals: 10 Biology + 8 Chemistry + 10 Physics = 28. Trilogy totals: 7 + 6 + 8 = 21. The seven that get dropped are the "biology only", "chemistry only" or "physics only" practicals, i.e. the ones that sit in topics that only appear on the separate GCSEs.
| Science | Dropped from Triple → Trilogy | Why it's dropped |
|---|---|---|
| Biology | Microbiology: effect of antiseptics or antibiotics on bacterial growth | Content is biology only within Cell biology |
| Biology | Plant responses: effect of light or gravity on seedling growth | Content is biology only within Homeostasis and response |
| Biology | Decay: effect of temperature on the rate of decay of fresh milk by measuring pH change | Content is biology only within Ecology |
| Chemistry | Titration of a strong acid with a strong alkali | Chemistry-only content within Chemical changes / Quantitative chemistry |
| Chemistry | Chemical tests for ions (flame tests, hydroxide precipitates, carbonate, halide and sulfate tests) | Chemistry-only content within Chemical analysis |
| Physics | Thermal insulators: effect of insulation on energy transfer | Physics-only content within Energy |
| Physics | Light: reflection off a plane mirror and refraction through a rectangular glass block | Physics-only content within Waves |
If you're on Trilogy, don't revise titration, antiseptic plates, phototropism, thermal insulators, decay (pH change in fresh milk), chemical tests for ions, or reflection and refraction as required practicals. They aren't required for you. The underlying science of some of them (waves, for example) does appear in Trilogy, just not as a required practical you need to describe end to end.
Study tips for the 21 practicals
Reading through the method isn't enough. Required practicals test whether you can think like a scientist, not whether you can recite a recipe. A few things that work:
Write the method out from memory for each practical, then check it against your notes. The steps you forgot are the ones that would have cost you marks. Pay particular attention to the small details AQA loves: incubating microbiology plates at 25 degrees Celsius rather than 37 (so dangerous pathogens don't thrive), taping agar lids rather than sealing them, inverting plates, controlling the volume of solution in osmosis experiments, blotting potato cylinders before weighing.
Practise drawing results tables with the correct headings, units and number of decimal places. AQA frequently asks you to complete or draw a table, and marks are awarded just for correct headings-with-units, consistent decimal places and the independent variable in the left column.
Sketch the graphs you'd expect for each practical. For osmosis, a line showing percentage change in mass against concentration that crosses zero at the isotonic point. For photosynthesis, a curve that rises and then plateaus. For force vs extension of a spring, a straight line through the origin until the limit of proportionality. Plotting accurately and labelling axes correctly is worth marks on its own.
Work through past paper questions on each practical. AQA recycles similar wording and structures year on year, and the mark schemes are a goldmine for the exact phrases they want. Our GCSE mock exams guide explains how to use mock periods to test your recall across all 21 practicals.
When the exam asks you to suggest improvements to a method, think in threes: how to improve accuracy (more precise equipment), how to improve reliability (more repeats and a mean), and how to improve validity (better control of variables).
How Cognito helps
Our AQA GCSE Combined Science courses cover every one of the 21 required practicals through short video lessons, worked examples and exam-style questions. Each practical gets its own lesson walking through the method, the variables, the results and the exam language. You can jump straight into the Combined Science Biology course, the Combined Science Chemistry course or the Combined Science Physics course and track your progress through the whole spec.
If you want a wider revision framework around the required practicals, our guide on how to revise for GCSE Science covers paper structure, timing, and how to layer required practicals into a week-by-week plan.
