AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Density of materials: Required practical activity 17: use appropriate apparatus to make and record the measurements needed to determine the densities of regular and irregular solid objects and liquids. Volume should be determined from the dimensions of regularly shaped objects, and by a displacement technique for irregularly shaped objects. Dimensions to be measured using appropriate apparatus such as a ruler, micrometer or Vernier callipers.
In this required practical you determine density using ρ = m ÷ V. For a regular solid such as a rectangular block, measure length, width and height with a ruler, micrometer or Vernier callipers,…
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Study notes
From the checked teaching notes for this specification point.
The idea
In this required practical you determine density using ρ = m ÷ V. For a regular solid such as a rectangular block, measure length, width and height with a ruler, micrometer or Vernier callipers, calculate volume, then measure mass with a balance and divide. For an irregular solid such as a stone, find mass on a balance, then use a displacement technique: record the starting volume of water in a measuring cylinder, lower the object in fully, and record the new volume; the volume of the object is the difference. For a liquid, measure the mass of an empty measuring cylinder, add a known volume of liquid, measure the new mass, and divide the mass of the liquid by its volume. Repeat readings and calculate a mean to reduce random error.
What earns the marks
- Selects a ruler, micrometer or Vernier callipers for the dimensions of a regular solid and records each measurement with a sensible unit.
- Calculates the volume of a regular solid from its measured dimensions, for example V = length × width × height.
- Uses a displacement technique for an irregular solid, reading the volume before and after immersion and finding the difference.
- Measures mass with a balance and calculates density using ρ = m ÷ V.
- For a liquid, measures the mass of the empty container, then the mass of container plus liquid, and uses the difference as the mass of the liquid.
- Repeats measurements and calculates a mean to reduce the effect of random error.
Common mistakes and how to put them right
Forgetting to subtract the initial water volume when using displacement.
Put it right by recording the start volume and the final volume and using the difference.
Using the mass of the container plus liquid as the mass of the liquid.
Put it right by subtracting the mass of the empty container.
Mixing units, such as using grams with centimetres cubed and then quoting kg/m³.
Put it right by converting consistently before calculating.
Exam tips
- Write a clear method with the apparatus named and the measurements you would take.
- State how you would improve reliability, such as repeating readings and calculating a mean.
- Show the equation ρ = m ÷ V and substitute values with units before giving the final answer.
Try the lesson
The start of the Density of materials: Required practical activity 17: use appropriate apparatus to make and record the measurements needed to determine the densities of regular and irregular solid objects and liquids. Volume should be determined from the dimensions of regularly shaped objects, and by a displacement technique for irregularly shaped objects. Dimensions to be measured using appropriate apparatus such as a ruler, micrometer or Vernier callipers. lesson, made from checked teaching notes for this specification point.
Have a go first
A student measures the mass of a regular solid cube as 54 g. The cube has a side length of 3 cm. What is the density of the cube?
Listen
In this required practical you determine density using ρ = m ÷ V. For a regular solid such as a rectangular block, measure length, width and height with a ruler, micrometer or Vernier callipers, calculate volume, then measure mass with a balance and divide. For an irregular solid such as a stone, find mass on a balance, then use a displacement technique: record the starting volume of water in a measuring cylinder, lower the object in fully, and record the new volume; the volume of the object is the difference. For a liquid, measure the mass of an empty measuring cylinder, add a known volume of liquid, measure the new mass, and divide the mass of the liquid by its volume. Repeat readings and calculate a mean to reduce random error. A strong answer earns marks for these points. Selects a ruler, micrometer or Vernier callipers for the dimensions of a regular solid and records each measurement with a sensible unit. Calculates the volume of a regular solid from its measured dimensions, for example V = length × width × height. Uses a displacement technique for an irregular solid, reading the volume before and after immersion and finding the difference. Measures mass with a balance and calculates density using ρ = m ÷ V. A common slip: Forgetting to subtract the initial water volume when using displacement. Instead, recording the start volume and the final volume and using the difference. Exam tip: Write a clear method with the apparatus named and the measurements you would take.
Key words
Say what each word means before you turn the card.
Displacement technique
Try answering aloud or in your head before turning the card.
Density
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Repeat readings
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Regular solid
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See every definition
- Displacement technique
- A way of finding the volume of an irregularly shaped object by recording the starting volume of water in a measuring cylinder, lowering the object in fully, and recording the new volume.
- Density
- Calculated from measured mass and volume using ρ = m ÷ V.
- Repeat readings
- Taking measurements more than once and calculating a mean to reduce the effect of random error.
- Regular solid
- An object whose volume is determined from its measured dimensions, for example V = length × width × height.
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Test your understanding of Density of materials: Required practical activity 17: use appropriate apparatus to make and record the measurements needed to determine the densities of regular and irregular solid objects and liquids. Volume should be determined from the dimensions of regularly shaped objects, and by a displacement technique for irregularly shaped objects. Dimensions to be measured using appropriate apparatus such as a ruler, micrometer or Vernier callipers.
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