AQA GCSE Physics · Particle Model of Matter
Density required practical
Determine the densities of regular and irregular solid objects and of liquids.
Density is mass ÷ volume. You find volume by measuring a regular solid, by displacement for an irregular one, or with a measuring cylinder for a liquid.
Equipment
- Top-pan balance
- Ruler (or vernier calipers)
- Eureka (displacement) can and measuring cylinder
- Regular solid (e.g. an aluminium block) and an irregular object (e.g. a stone)
- Liquid (e.g. water)
- Cotton thread
Variables
- Independent you change
- The object or liquid being tested
- Dependent you measure
- Its density (from mass and volume)
- Control you keep the same
- Same balance, zeroed each time
- Read the measuring cylinder at eye level
Method
- 1
Regular solid: measure its mass on a balance, then its length, width and height. Volume = length × width × height.
- 2
Irregular object: measure its mass. Fill a eureka can with water up to the spout.
- 3
Lower the object in on a thread and collect the displaced water in a measuring cylinder. Its volume is the volume of water displaced.
- 4
Liquid: put an empty measuring cylinder on the balance and zero it. Pour in the liquid and record its mass and volume.
- 5
Calculate density = mass ÷ volume for each.
- 6
Repeat each measurement and take a mean.
Worked example
Three objects measured with the same balance.
| Object | Mass (g) | Volume (cm³) | Density (g/cm³) |
|---|---|---|---|
| Aluminium block (5 × 3 × 2 cm) | 81.0 | 30.0 | 2.70 |
| Stone (displacement) | 119.6 | 46.0 | 2.60 |
| Water | 50.0 | 50.0 | 1.00 |
Working
Block volume = 5.0 × 3.0 × 2.0 = 30.0 cm³
Density = mass ÷ volume = 81.0 ÷ 30.0 = 2.70 g/cm³
To convert to kg/m³, multiply by 1000: 2.70 g/cm³ = 2700 kg/m³
Conclusion
The aluminium block has a density of 2.70 g/cm³ (2700 kg/m³), the stone 2.60 g/cm³ and water 1.00 g/cm³. Objects denser than water sink; less dense ones float.
Risks
- Spilt water on the floorMop it up straight away.
- Dropping heavy objects into the canLower them gently on a thread.
Common mistakes
- Dropping the object into the eureka can. It splashes water out, so the measured volume is too big.
- Not filling the eureka can right up to the spout first.
- Mixing units. Keep mass in g with volume in cm³ (g/cm³), or kg with m³ (kg/m³).
Better results
- Use vernier calipers or a micrometer for more precise length measurements.
- Use a smaller measuring cylinder for the displaced water, so the scale is more precise.
- Repeat each measurement and calculate a mean.
Launching November 2026
7 exam questions on this practical.
Practise the method, the variables, the maths and what the results mean, then revise the Particle Model of Matter flashcards. It opens to students soon: join the waitlist and we’ll email you once, when it does.