O-Level Chemistry Measurement Accuracy Lab

TL;DR
SEAB’s MMO descriptors emphasise setting up apparatus correctly, recording measurements to appropriate precision, and making justified decisions about significant figures (SEAB 2026 syllabus, pp. 25–26).
Pair that with the mathematical requirements on rounding, unit conversions, and proportional reasoning (p. 32) and you get a high-value practice circuit: calibrate instruments, record data cleanly, and critique accuracy in ACE responses.
Use this lab to warm up before titrations, calorimetry, or gas-collection tasks so precision habits become automatic.

1 | Core measurement expectations

• Balances (0.01 g or better). Zero before weighing, record to two decimal places, state mass differences instead of raw readings when appropriate.
• Burettes (0.05 cm³). Read at eye level, include both initial and final readings, report titres to 2 decimal places (last digit 0 or 5).
• Pipettes (25 cm³). Use pipette filler, ensure drain time is consistent, blowout instructions only if pipette is marked “TD blowout”.
• Gas syringes & measuring cylinders. Note calibration increments; read meniscus at eye level; ensure plunger moves freely without leaks.
• Thermometers & data loggers. Stir before reading, allow temperature to stabilise, record to the nearest 0.5 °C (glass) or 0.1 °C (digital).
• Timing devices. Use stopwatches with 0.1 s precision; for slower reactions, note ±0.5 s uncertainty due to human reaction time.

2 | Planning statements for accuracy drills

1. Balance calibration. “Zero the electronic balance, place a standard 100.00 g mass, record deviation, and apply correction to subsequent measurements.”
2. Burette practice. “Rinse burette with solution, fill above zero, open tap to expel air bubbles, set meniscus to 0.00 cm³ ±0.02 cm³, record initial and final readings to 2 decimals.”
3. Pipette delivery test. “Deliver 25.00 cm³ of distilled water into a pre-weighed beaker, weigh to confirm mass ≈ 25.00 g at 25 °C, calculate percentage deviation.”
4. Thermometer cross-check. “Measure temperature of an ice–water mixture (expect 0 °C) and boiling water (100 °C at 1 atm), note systematic offset if readings differ.”
5. Gas syringe leak test. “Fill syringe with 50 cm³ air, leave plunger under load for 2 min, note changes; apply petroleum jelly to seal if drift exceeds 1 cm³.”

Include hazard notes: glass breakage, chemical exposure during rinses, hot water during thermometer checks.