A student is investigating how the temperature of water changes when it is heated. They record the temperature every 30 seconds. Explain how the student should ensure their results are reliable and how they should identify and deal with any anomalous results.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A student heats 100 cm³ of water and records the temperature at 30-second intervals. They want to make sure their investigation produces reliable results.
Model answer (5 marks)
1. Repeat the experiment at least three times to obtain repeat readings.
2. Calculate a mean (average) from the repeat readings to improve reliability.
3. Identify an anomalous result as one that does not fit the pattern or trend of the other results.
4. Identify anomalous results by comparing each result to the others or to the overall trend.
5. Exclude anomalous results from the calculation of the mean, or repeat the experiment to replace the anomalous result.
2. Calculate a mean (average) from the repeat readings to improve reliability.
3. Identify an anomalous result as one that does not fit the pattern or trend of the other results.
4. Identify anomalous results by comparing each result to the others or to the overall trend.
5. Exclude anomalous results from the calculation of the mean, or repeat the experiment to replace the anomalous result.
Examiner tips
- Use the command word ‘explain’ to describe the steps, not just list them. Show the calculation of a mean if you mention it. Explain why repetition and averaging improve reliability.
Common mistakes
- Failing to mention that the experiment should be repeated at least three times. Not defining what an anomalous result is. Including anomalous data in the mean instead of excluding it.
Mark scheme (5 marks)
- The student should repeat the experiment (at least three times) to obtain repeat readings
- Calculate a mean (average) from the repeat readings to improve reliability
- An anomalous result is one that does not fit the pattern/trend of the other results
- Anomalous results should be identified by comparing each result to the others / to the overall trend
- Anomalous results should be excluded from the calculation of the mean / the experiment should be repeated to replace the anomalous result
Key terms in this question
Related
- All OCR A-Level Chemistry A (H432) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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