Year 7 Science · AC9S7I03
Select equipment and record precise data
Quantity → range/capacity → resolution → safety/setting → recording.
Learning intention & success
Students select equipment that matches the quantity and expected range, explain resolution, distinguish precision from accuracy, use digital tools critically, and record raw data with correct units and justified decimal places.
Model the selection decision
Scenario: measure 15 mL of liquid. Compare a 1 L beaker, 100 mL cylinder and 25 mL cylinder.
Model: The 25 mL cylinder has sufficient capacity and usually finer graduations, so it gives more useful resolution for 15 mL.
Precision, accuracy & errors
- Resolution: smallest readable increment.
- Precision: fineness/repeatability of measurement.
- Accuracy: closeness to an accepted/reference value.
- Calibration/zero error: can shift readings systematically.
- Parallax: read analogue scales at eye level.
- Reaction time: limits manually timed short events.
More decimal places do not create accuracy. Record only precision justified by the instrument.
Digital tools
Stopwatches, balances, temperature/light/pH/soil-moisture sensors and data loggers can improve resolution or automate sampling, but still require calibration, sensible sampling intervals, battery/setup checks and verification of unusual outputs.
Recording data
Keep raw readings. Put quantity and unit in headings, for example Temperature (°C). Use consistent units and decimal places justified by resolution. Flag missing/anomalous readings rather than silently changing them. Separate measured values from qualitative observations.
Guided → independent
We do: choose between thermometers with different ranges and resolutions for 20–70 °C water.
You do: design a raw-data table for temperature every 30 s for 5 min, then justify a suitable sensor and sampling interval.
Exit ticket: explain one way a very precise measurement could still be inaccurate.