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GCSE Combined Science · key term
An electronic instrument that uses a probe placed in a solution to measure its pH and display a numerical reading.
Used by OCR
Specification C3.3k · Chemistry Paper 1
Revise: Measuring pHYou can estimate pH by observing the colour of universal indicator, or measure it electronically using a pH meter. Both methods are useful, but they provide different levels of detail.
Chemistry, Combined Science
An instrument with a probe that measures the pH of a solution and displays a numerical reading.
For a pH meter, state that you calibrate it, rinse the probe between samples and wait for a steady reading.
A pH meter gives a more precise numerical reading, not a guaranteed exact value. Correct calibration and careful use matter.
Universal indicator estimates pH; a pH meter gives a numerical reading. Compare indicator colours with the chart supplied.
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A pH meter uses a probe to give a numerical reading, avoiding the need to judge a colour. If necessary, calibrate it using a buffer solution of known pH. Rinse the probe with distilled water, place its sensing end in the sample and record the reading once it has stabilised.
