AQA · Chemistry · 8462
GCSE Chemistry: Chemical measurements
Quantitative chemistry · AQA GCSE Chemistry (8462), specification point 4.3.1.4. Cards are generated from the exam board's own specification for "Chemical measurements", and every card links back to the page it came from. Specification © AQA — used with attribution.
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Whenever a measurement is made there is always some ? about the result obtained.
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uncertainty
Can a chemical measurement ever be made with zero uncertainty?
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No — every measurement carries some uncertainty about the result obtained.
Which statistic of a set of repeated measurements is used as a measure of uncertainty?
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The range of the measurements about the mean.
The uncertainty of a set of repeated measurements is estimated from the ? of the results about the mean.
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range
How is the range of a set of measurements calculated?
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Largest value minus smallest value.
Repeated titres have a mean of 25.0 cm³ and a range of 0.4 cm³. State the result with its uncertainty.
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25.0 ± 0.2 cm³ — the uncertainty is half the range about the mean.
Why represent the distribution of a set of repeated results?
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To show how spread out the results are, which allows the uncertainty to be estimated.
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