GCSE Physics resources

AQA GCSE Particle model of matter

Density Required Practical

Measure mass with a balance. For a regular object, calculate volume from dimensions; for an irregular object, use water displacement. Read scales at eye level and remove trapped air bubbles.

AQA 8463AQA 8464 GCSE PhysicsCombined Science: Trilogy FoundationHigher

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The revision snapshot

Measure mass with a balance. For a regular object, calculate volume from dimensions; for an irregular object, use water displacement. Read scales at eye level and remove trapped air bubbles.

By the end, you should be able to:

  • Explain measuring density of regular and irregular objects.
  • Apply the particle model of matter model, evidence or method to an unfamiliar exam context.
  • Recognise and correct this wrong turn: Using centimetres and metres inconsistently.

Before you revise

Diagnostic question

Choose an answer from memory. Your result tells you what to watch for in the guide.

Which statement correctly summarises density required practical?

Core revision guide

Learn the model, then use it

Density Required Practical questions become manageable when the central model, evidence and exam method are kept together. Read the explanation, test the misconception and then apply the idea without looking back.

Measuring density of regular and irregular objects

Measure mass with a balance. For a regular object, calculate volume from dimensions; for an irregular object, use water displacement. Read scales at eye level and remove trapped air bubbles.

Build the physics picture

For a regular object, calculate volume from measured dimensions. For an irregular object, the rise in water level is its volume. Read the bottom of the meniscus at eye level, make sure the object is fully submerged and remove bubbles that would make the volume look too large.

The relationship for this guide

Density: ρ = m ÷ V (kg/m³, kg, m³). Choose each relationship from the physical change described, convert quantities into compatible units and keep the unit beside the final answer.

Regular solid, irregular solid and liquid density methods use dimensions, displacement and a known volume respectively.
Choose the volume method for the sample, find mass with a balance and calculate density as mass divided by volume.Open the full-size exam diagram
Densityρ = m ÷ Vkg/m³, kg, m³

Misconception clinic

Replace the tempting answer

Read each belief, say what is wrong with it, then compare your correction.

Tempting idea: Using centimetres and metres inconsistently.

Use instead: Measure mass with a balance. For a regular object, calculate volume from dimensions; for an irregular object, use water displacement. Read scales at eye level and remove trapped air bubbles.

Tempting idea: Forgetting to subtract initial water level.

Use instead: For a regular object, calculate volume from measured dimensions. For an irregular object, the rise in water level is its volume. Read the bottom of the meniscus at eye level, make sure the object is fully submerged and remove bubbles that would make the volume look too large.

Tempting idea: Not identifying the volume method for the object shape.

Use instead: Give apparatus, measurements, equation, unit conversion, repeats and one uncertainty or validity improvement.

Retrieval practice

Quick checks

1. Which exam method is most reliable for density required practical?

2. Which statement correctly applies density required practical to a question?

3. A pupil writes: “Using centimetres and metres inconsistently.” Which replacement is accurate?

Worked examples

See the method being built

These examples expose the difference between a secure measuring density of regular and irregular objects method and the common error “Using centimetres and metres inconsistently.”.

Example 1 · Regular-object method

Describe how to find the density of a metal cuboid.

  1. Measure mass with a balance.
  2. Measure length, width and height with a ruler/calipers.
  3. Calculate V then ρ = m/V.
Show the answer

Measure mass and dimensions, calculate volume = lwh, then divide mass by volume using consistent units.

Example 2 · Irregular-object method

Describe how to find density of an irregular stone.

  1. Measure mass on a balance.
  2. Record water-level increase when fully submerged.
  3. Use ρ = m/V.
Show the answer

The displaced-water volume equals the stone volume; divide its mass by this volume.

Example 3 · Spot a systematic issue

Air bubbles cling to a submerged object. Explain the effect.

  1. Bubbles increase apparent displacement.
  2. Apparent volume is too large.
  3. Use ρ = m/V.
Show the answer

The calculated density is too small because mass is divided by an overestimated volume.

Exam precision

Exam technique: Measuring density of regular and irregular objects

Do this: Give apparatus, measurements, equation, unit conversion, repeats and one uncertainty or validity improvement.

Independent practice

Exam-style questions

Write an answer before opening the marking guidance. Then edit the exact phrase or step that would gain the next mark.

1. Name the apparatus used to measure mass in the density practical.

[1 mark]
Show marking guidance and model answer

Marking guidance: Award one mark for the precise statement shown in the model answer.

Model answer: A balance.

2. State how to calculate the volume of a cuboid.

[3 marks]
Show marking guidance and model answer

Marking guidance: Award one mark for the correct relationship, one for a valid substitution and one for the final answer with its unit.

Model answer: Length × width × height.

3. State how to find an irregular object’s volume.

[3 marks]
Show marking guidance and model answer

Marking guidance: Award one mark for the correct relationship, one for a valid substitution and one for the final answer with its unit.

Model answer: Use the increase in water volume on submersion.

4. An object has mass 0.16 kg and volume 2.0 × 10⁻⁵ m³. Calculate density.

[3 marks]
Show marking guidance and model answer

Marking guidance: Award one mark for the correct relationship, one for a valid substitution and one for the final answer with its unit.

Model answer: ρ = 0.16 ÷ 2.0 × 10⁻⁵ = 8000 kg/m³.

5. Give one control/quality step for a displacement method.

[1 mark]
Show marking guidance and model answer

Marking guidance: Award one mark for the precise statement shown in the model answer.

Model answer: Ensure the object is fully submerged with no air bubbles and read at eye level.

6. Explain why repeated measurements of dimensions help.

[3 marks]
Show marking guidance and model answer

Marking guidance: Award up to 3 marks for distinct physics points joined into a clear cause-and-effect chain.

Model answer: They reduce random uncertainty; a mean gives a more reliable volume.

Questions pupils ask

Density Required Practical FAQs

What is the main idea in Density Required Practical?

Measure mass with a balance. For a regular object, calculate volume from dimensions; for an irregular object, use water displacement. Read scales at eye level and remove trapped air bubbles.

What mistake should I avoid in Density Required Practical?

Using centimetres and metres inconsistently. For a regular object, calculate volume from measured dimensions. For an irregular object, the rise in water level is its volume. Read the bottom of the meniscus at eye level, make sure the object is fully submerged and remove bubbles that would make the volume look too large.

Useful next steps

Connect this guide to your next task

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