Apparatus and techniques across biology, chemistry and physics
Practical Skills (PS) is examined directly in the CCEA written practical paper and threads through every Biology, Chemistry and Physics unit. Marks are routinely lost not for getting the wrong answer but for poor apparatus choice, missing units or unsafe procedure.
Choosing the right apparatus
| Quantity | Best apparatus | Resolution |
|---|---|---|
| Volume of liquid (rough) | Measuring cylinder | ±1 cm³ |
| Volume of liquid (titration) | Burette / pipette | ±0.05 cm³ / ±0.1 cm³ |
| Mass | Top-pan balance | 0.01 g (or 0.001 g) |
| Length | Ruler / vernier callipers | 1 mm / 0.02 mm |
| Time | Stopwatch | 0.01 s (read to 0.1 s — reaction time) |
| Temperature | Liquid-in-glass thermometer | 1 °C (digital probe 0.1 °C) |
| Current / pd | Ammeter / voltmeter | depends on range |
Reading scales correctly
Read at eye level (no parallax error). For liquids, read the bottom of the meniscus — except mercury (read top). Always quote a reading to the resolution of the instrument: 24.5 cm³, not 24 cm³.
Common safety rules across the three sciences
- Wear safety goggles whenever heating, mixing acids/alkalis, or handling living micro-organisms.
- Tie back hair, no loose clothing, stand for hot/practical work in chemistry.
- Use heatproof mats; place hot apparatus on a tripod, never on the bench.
- Acids and alkalis: dilute and rinse spills with water; report to the teacher.
- Electrical: low-voltage DC supplies only; switch off before changing components.
Standard techniques
- Filtration (separating insoluble solid from liquid) — folded filter paper in funnel; the residue stays in the paper, the filtrate passes through.
- Evaporation / crystallisation — heat in an evaporating basin; stop when the saturation point is reached, then leave to cool to crystallise.
- Pipetting — fill to the mark, deliver and touch the tip on the inside of the conical flask. Never blow out the last drop.
CCEA tip
When a written practical paper asks you to "describe a method", award yourself one mark per distinct, ordered step (apparatus → measurement → repeat → control → result). Aim for 5-6 numbered steps to bank QWC marks.
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