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Students lose marks in the AQA GCSE Combined Science: Trilogy (8464) exam for predictable, avoidable reasons. This lesson catalogues the most common mistakes — drawn from examiner reports and mark schemes — and shows you exactly how to avoid each one.
AQA publishes examiner reports after every exam series. These reports highlight the same errors year after year. By learning what these mistakes are, you can avoid them and pick up marks that most students leave behind.
Exam Tip: Many students have the knowledge to score higher but lose marks through avoidable errors. This lesson could be worth 10–20 extra marks across your six papers.
This is the number one source of lost marks according to every examiner report.
| Error | Example | What to do instead |
|---|---|---|
| Answering a different question from the one asked | Question says "Explain why…" but student writes "Describe…" | Underline the command word and check your answer matches it |
| Ignoring information given in the question | Question provides data but student does not refer to it | Read the question twice and use the data provided |
| Writing about the wrong topic | Question asks about respiration but student writes about photosynthesis | Underline key scientific terms in the question |
Exam Tip: Read the question at least twice. Underline the command word and any key terms. Check your answer addresses exactly what was asked.
| Error | Consequence | What to do |
|---|---|---|
| Only writing the final answer | If the answer is wrong, you get 0 marks | Write the equation → substitute → calculate → state the unit |
| Showing incomplete working | You may miss method marks | Show every step, even if it seems obvious |
| Not including units | You lose the unit mark (often worth 1 mark) | Always write the unit next to your answer |
Question: "Calculate the kinetic energy of a 1200 kg car travelling at 15 m/s."
Poor layout: "1200 × 15² ÷ 2 = 135000"
Good layout: "KE = ½ × m × v² KE = ½ × 1200 × 15² KE = ½ × 1200 × 225 KE = 135,000 J"
Exam Tip: The good layout earns marks for the equation (1 mark), correct substitution (1 mark) and correct answer with unit (1 mark). The poor layout only earns marks if the final number is correct.
This has been covered in Lesson 2, but it is so common that it deserves repeating.
| Command | What to do | Example answer |
|---|---|---|
| Describe | Say what happens — use data if available | "The rate of reaction increased as concentration increased." |
| Explain | Say what happens and why — use scientific reasoning | "The rate increased because higher concentration means more particles per unit volume, leading to more frequent collisions." |
Exam Tip: If you write "because" in a describe answer, you are probably explaining. If you do not write "because" in an explain answer, you are probably only describing.
Examiners award marks for precise scientific terminology. Vague language does not score.
| Vague (no marks) | Precise (marks awarded) |
|---|---|
| "The stuff moves through the body" | "Oxygenated blood is pumped from the left ventricle through the aorta" |
| "It gets hotter" | "The temperature of the solution increased by 12°C" |
| "Energy is lost" | "Energy is transferred to the thermal energy store of the surroundings by heating" |
| "The particles move faster" | "The particles have greater kinetic energy, so they collide more frequently" |
Exam Tip: In AQA science, energy is transferred or dissipated, not "lost" or "used up". Using the correct terminology shows the examiner you understand the concept.
| Common unit errors | Correct unit |
|---|---|
| Energy in "w" or "W" | Energy is in J (joules); power is in W (watts) |
| Force in "j" | Force is in N (newtons) |
| Density in "g" | Density is in kg/m³ or g/cm³ |
| No unit at all | Always write the unit, even if the question does not explicitly ask |
| Error | How to fix it |
|---|---|
| Axes the wrong way round | IV on x-axis, DV on y-axis — every time |
| No axis labels or units | Write the variable name and the unit in brackets |
| Joining the dots | Draw a line of best fit (straight or curved) |
| Using a tiny scale that wastes the grid | Use more than half the grid in each direction |
| Inaccurate plotting | Double-check each point against both axes |
When comparing, you must write about both items. A statement about only one does not score.
| One-sided (no marks) | Two-sided (marks) |
|---|---|
| "Arteries have thick walls." | "Arteries have thick walls whereas veins have thinner walls." |
| "Diamond is hard." | "Diamond is hard because each carbon is bonded to four others, whereas graphite is soft because the layers can slide over each other." |
Some questions have multiple parts within a single box on the paper. A common error is answering only the first part.
Example: "Describe the results shown in the graph and explain the pattern."
This requires:
Exam Tip: Count the command words in the question. If there are two, your answer needs two parts.
Examiners specifically look for — and penalise — misconceptions:
| Misconception | Correct understanding |
|---|---|
| "Energy is created / destroyed" | Energy is transferred between stores; it is conserved (never created or destroyed) |
| "Atoms are alive / want to be stable" | Atoms are not alive; they react because of electrostatic forces and energy changes |
| "Electricity flows out of both ends of a battery" | Current flows in a complete circuit from one terminal through the components and back |
| "Heavier objects fall faster" | In a vacuum, all objects fall at the same rate (9.8 m/s²); air resistance can differ |
| "Evolution happens because organisms want to change" | Evolution occurs through random mutations and natural selection — there is no intention |
| "Metals conduct electricity because they have electrons" | Metals conduct because they have delocalised (free) electrons that can carry charge |
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