A student uses a measuring cylinder to find the volume of a small irregularly shaped stone. Describe how the student would use the measuring cylinder to find the volume of the stone, and explain why taking the measurement more than once and calculating a mean reduces the uncertainty in the result.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
1. Fill the cylinder with water and note the initial level.
2. Submerge the stone completely, note the new level.
3. The stone’s volume = final level – initial level.
4. Repeating the measurement and taking the mean minimises random errors, lowering the percentage uncertainty and giving a more reliable result.
2. Submerge the stone completely, note the new level.
3. The stone’s volume = final level – initial level.
4. Repeating the measurement and taking the mean minimises random errors, lowering the percentage uncertainty and giving a more reliable result.
Examiner tips
- Use the word ‘difference’ to show the calculation of volume.
- Show that the mean reduces random error, not systematic error.
- Mention that the uncertainty is inversely proportional to the square root of the number of trials.
Common mistakes
- Failing to submerge the stone fully, giving an incorrect volume.
- Confusing mean with median or mode.
- Claiming that taking more measurements increases precision but not explaining the reduction of random error.
Mark scheme (4 marks)
- Partially fill the measuring cylinder with water and record the initial water level (volume reading)
- Submerge the stone completely in the water and record the new (final) water level
- The volume of the stone equals the difference between the final and initial water level readings
- Repeating measurements and calculating a mean reduces the effect of random errors / reduces the percentage uncertainty, giving a more reliable result
Key terms in this question
measuring cylinder · volume · mean
Related
- All Cambridge International IGCSE Physics (0625) revision notes →
- How to answer a "Describe and Explain" question →
- Decode the mark scheme abbreviations →
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