AQA GCSE Physics Physics Paper 1 (Foundation), June 2022: Question 10

✅ Correct Answer / Level 3 Criteria (5–6 Marks)

A full-mark response requires a logical, sequential method covering mass measurement, volume measurement of an irregular solid, and the final density calculation.

• Measure the mass of the rock using a balance (scales).
• Fill a displacement can (Eureka can) with water up to the spout, or part-fill a measuring cylinder.
• Place the rock completely into the water and measure the volume of displaced water (or final volume minus initial volume).
• Use the formula: density = mass ÷ volume .

💡 Key Knowledge

Irregular objects cannot use geometric formulas (like length × width × height). Instead, they rely on Archimedes' principle of displacement: the volume of water displaced equals the volume of the submerged object.

🧠 Exam Technique

Write your method in clear, numbered bullet points or chronological sentences. Examiners look for explicit instructions: what equipment is used, how it is set up, and what readings are recorded.

❌ Common Errors

• Forgetting to state that the Eureka can must be filled right up to the level of the spout before adding the rock.
• Failing to link the displaced water volume directly to the volume of the rock.
• Omitting the final density calculation step.

✅ Correct Answers

Maximum density = 2.65 g/cm³

Minimum density = 2.45 g/cm³

📐 Working Out

1. Identify the given measured value: 2.55 g/cm³
2. Identify the uncertainty: ± 0.10 g/cm³
3. Maximum: 2.55 + 0.10 = 2.65 g/cm³
4. Minimum: 2.55 − 0.10 = 2.45 g/cm³

🧠 Exam Technique

Both values must be correct to secure the single mark. Double-check your addition and subtraction with the given uncertainty value.

✅ Correct Answer

Tick: Chalk or flint

💡 Key Knowledge

Compare the calculated range from question 10.2 ( 2.45 to 2.65 g/cm³ ) against the density ranges given in Table 3:

• Basalt: 2.90 ± 0.10 (2.80–3.00) — No overlap
• Chalk: 2.35 ± 0.15 (2.20–2.50) — Overlaps at 2.45–2.50
• Flint: 2.60 ± 0.10 (2.50–2.70) — Overlaps at 2.50–2.65
• Sandstone: 2.20 ± 0.20 (2.00–2.40) — No overlap
• Slate: 2.90 ± 0.20 (2.70–3.10) — No overlap

✅ Correct Answers (Any 2 points)

• A mean (average) can be calculated.
• This reduces the effect of random errors.
• Allow: Anomalies can be identified and removed.

💡 Key Knowledge

Random errors cause individual readings to scatter unpredictably above and below the true value. Repeating measurements and calculating a mean helps smooth out these variations.

❌ Common Errors

Students often incorrectly state that repeating measurements "reduces systematic errors" or "improves accuracy" without explaining how (i.e., through calculating a mean or spotting anomalies). Systematic errors (like a zero error on a balance) cannot be fixed by repetition!