7. Assessed scientific skills

Group related information, put sequences in a logical order and use a labelled table, list or graph when it reveals structure more clearly than prose.

Every presented value needs an unambiguous heading, unit and sensible precision. State the source or condition when it affects interpretation.

The words 'distance equals speed multiplied by time' translate to d = vt. A straight distance–time line with constant gradient translates to constant speed.

Translate back into the original form as a check. If the reverse statement changes the meaning or units, the translation is incomplete.

For race times 22.50 s and 23.20 s, the smaller time wins and the winning margin is 23.20 − 22.50 = 0.70 s.

Use 'directly proportional' only when the ratio is constant and the relationship would pass through the origin. A general increase alone is not enough.

Make the direction of cause and effect explicit: state the changed condition, the physical mechanism and the resulting change.

For a comparison, explain both sides or use an explicit 'greater because...' statement with the controlled condition.

Interpolation predicts within the measured range and is usually safer. Extrapolation predicts beyond it and assumes the relationship continues.

For a qualitative problem, trace how one change affects the next quantity through a physics principle. For a quantitative problem, the same reasoning selects the correct equation before arithmetic begins.

Unfamiliar wording does not require a new law. Identify the familiar quantities and relationships hidden in the context.

Identify hazards before starting, use the stated protective controls, keep the setup stable and follow the operating sequence so that safety and measurement validity are both preserved.

Read scales at eye level where parallax is possible, check zero before measuring, place the instrument correctly and record only precision justified by the scale.

Where calibration is required, use known fixed values and wait for a stable reading before marking the scale—for example melting ice for 0 °C and steam above boiling water for 100 °C on a thermometer.

State how results will be processed or graphed so the planned measurements actually answer the investigation aim.

For a uniform thermometer scale, use the fraction of the distance between the 0 °C and 100 °C fixed points. If the liquid is 8 mm below 0 °C and extends 64 mm above 0 °C while the fixed-point separation is 80 mm, the indicated temperature is (64/80) × 100 = 80 °C.

Qualitative observations also need precise language: record colour, motion, sound or state changes without adding an explanation to the observation column.

Use a best-fit line or curve to judge the overall relationship rather than joining points dot-to-dot. A scattered point should be investigated, not silently deleted.

A conclusion should state the supported relationship and its range, then acknowledge any limitation that materially weakens it.

Repeats reduce random uncertainty and help reveal anomalies; they do not remove a systematic zero error or heat loss.

Where possible, state the direction of bias. If energy lost to the surroundings is wrongly treated as heating the sample, a calculated specific heat capacity may be too high.

For direct proportion, doubling one quantity doubles the other; for inverse proportion, doubling one halves the other. A mathematical model must match the stated physical conditions.

The symbol Δ means a change: Δx = final x − initial x. It is not automatically the final value itself.

Write standard form as a × 10ⁿ with 1 ≤ |a| < 10. Preserve positive whole-number indices correctly in algebraic expressions.

For a scale diagram, state the scale, draw each length and direction accurately with ruler and protractor, construct the resultant, then convert its measured length back to the physical value.

Metric conversion factors must be raised to match the dimension: 1 cm = 10⁻² m, so 1 cm² = 10⁻⁴ m² and 1 cm³ = 10⁻⁶ m³.

Use N, S, E and W and specify clockwise or anticlockwise angles from a clear reference direction.

A graph reveals direction, shape and proportionality. Distinguish a straight relationship with non-zero intercept from direct proportionality.

A micrometer with 50 divisions across a 0.50 mm thimble movement has resolution 0.50/50 = 0.01 mm; record readings to that precision after checking zero error.

Calculate gradient = change in vertical quantity/change in horizontal quantity, using points on the best-fit line rather than necessarily raw data points. Give two or three significant figures and derive its unit from the axes.

To find the gradient of a curve at a chosen point, draw a tangent that just touches the curve there and follows its local direction. Choose two well-separated points on the tangent, then calculate Δy/Δx.

Use a large gradient triangle to reduce the percentage effect of reading uncertainty, and include the gradient unit formed from vertical-axis unit divided by horizontal-axis unit.