Density of materials — AQA GCSE Physics
Test yourself on Density of materials with AQA GCSE practice questions.
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Density of materials explained
Both methods start the same way: measure the mass on a balance and calculate density from ρ = m ÷ V.
Read the full explanation
For a regular solid, measure the sides with a ruler, or with a micrometer or Vernier callipers for small dimensions, and calculate the volume from those dimensions, so for a cube V = side³. For an irregular solid such as a small statue you cannot calculate the volume, so use displacement: fill a eureka can to the spout, lower the object in until it is fully submerged, and collect the displaced water in a measuring cylinder, because the volume of water displaced equals the volume of the object. For a liquid, find the mass of an empty measuring cylinder, add the liquid, reweigh, and subtract.
Your focus
- Describe, in a logical sequence, a method for finding the density of a regularly shaped solid.
- Describe how to find the volume of an irregular object by displacement and say why the two volumes are equal.
- Calculate a density from measured mass and volume data and give the answer in a correct unit.
Density of materials exam tips
Marking Points
- marked by levels out of 6, not by separate points: Level 1 = 1-2 marks, Level 2 = 3-4 marks, Level 3 = 5-6 marks for a method that would give a valid outcome with all key steps identified and logically sequenced
- credited within the level: measure the mass of the object on a balance
- credited within the level: find the volume of a regular object from its measured dimensions, using a ruler, a micrometer or Vernier callipers as the size requires
- credited within the level: lower an irregular object until it is fully submerged in a displacement can and collect the water that overflows in a measuring cylinder
- credited within the level: the volume of water displaced equals the volume of the object
- credited within the level: calculate the density from ρ = m ÷ V
Examiner Tips
- 💡Six-mark method answers are marked by levels, so put the steps in a logical order another person could follow.
- 💡Name the instrument for every measurement: balance, ruler or callipers, measuring cylinder.
- 💡Finish the method with the equation you would use, because the calculation step is part of the top level description.
Common Mistakes
- weighing the liquid in its container and forgetting to subtract the mass of the empty container
- using a ruler on an irregular object and calling the result its volume
- not submerging the object completely, so the volume displaced is too small
- mixing grams with cubic metres and reporting a density that is wrong by a factor of a thousand