Practical skills
The four skills of the Physics practical paper: planning, measuring and observing, presenting data, and analysing and evaluating results.
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Before you begin
The practical paper tests four skills: planning an investigation, taking measurements, presenting data, and analysing and evaluating results. The G3 Physics and O-Level Physics papers test the same skills in the same way, so these lessons serve both courses. Learn each skill here, then use them in the practical investigations, starting with measurement and density.
Be comfortable with: range, resolution, parallax and zero error from measurement.
Learning goals
- Measurements of length, mass, temperature, time interval, volume of liquids/solids and force (e.g. weight) using appropriate instruments
- Determination of the resistance of a circuit component
Syllabus statements covered
- Measurements of length, time interval, volume, mass and weight, temperature, current and voltage using the listed instruments
- Determination of the density of a liquid, or of a regularly or irregularly shaped solid that sinks in water
- Determination of the value of the acceleration of free fall
- Investigation of the effects of balanced and unbalanced forces
- The principle of moments
- Determination of the position of the centre of gravity of a plane lamina
- Investigation of the factors affecting transfer of energy by thermal processes
- Determination of heat capacities of materials
- Latent heat of substances
- The law of reflection
- Determination of the position and characteristics of an optical image formed by a plane mirror or a thin converging lens
- The refraction of light through glass blocks
- The principle of total internal reflection
- The focal length of lenses
- Determination of the speed, wavelength and frequency of waves
- Determination of the resistance of a circuit
- Investigation of the magnetic effect of current in a conductor
- Investigation of the effects of electromagnetic induction
Lessons
Work through them in order.
Paper 3 skill areas
- Planning a physics investigationIdentify variables, select apparatus, write a reproducible method and match risks to precautions.PracticalSupporting
- Manipulation, measurement and observationFollow instructions, set up apparatus and record observations with justified precision.PracticalSupporting
- Presenting practical dataConstruct tables, process readings, choose graph scales and calculate a defensible gradient.PracticalSupporting
- Analysing conclusions and evaluating experimentsUse evidence for conclusions, identify significant errors and propose matched improvements.PracticalSupporting
Practical investigations
- Measurement and density investigationsChoose suitable instruments, correct readings and determine density from the mass and volume of the same sample.
- Investigating motion and balanceUse motion data to test forces and free fall, then use perpendicular distances and suspension lines to investigate balance.
- Thermal investigations and energy measurementsMake fair cooling comparisons and distinguish heat capacity, specific heat capacity and specific latent heat while evaluating energy losses.
- Investigating rays and optical imagesTrace rays from the normal, locate real and virtual images, and test total internal reflection and focal length.
- Measuring wavesMeasure spatial intervals and repeated cycles, match wavelength and frequency, and determine wave speed.
- Electrical and magnetic investigationsUse paired circuit readings to find resistance, then test field direction and induction by changing one factor at a time.
Practise and check
Or choose
Topic reference
Quick reference
| Skill area | What you do | Check before you move on |
|---|---|---|
| Planning | choose variables, apparatus and a method; say how the results answer the question | one variable changed, controls named, processing stated, a real hazard with its precaution |
| Measurement and observation | set up apparatus, take readings, record what you see | zero, range, unit, eye level, steady reading |
| Presentation of data | tables, graphs and gradients | quantity/unit headings, even scales, best-fit line, large gradient triangle |
| Analysis and evaluation | draw a conclusion; find errors and improvements | proportional means through the origin; source, effect and a matched fix |
Core knowledge to remember
- The practical paper lasts 1 h 50 min and has 40 marks, worth 20% of the course. Section A has 20 marks of practical work in one or two questions; Section B is one compulsory 20-mark question.
- Planning carries 15% of the paper’s marks; measurement and observation, presentation, and analysis and evaluation together carry 85%.
- Change one variable at a time, measure the effect, and keep the other variables that matter the same.
- Record readings to the precision of the instrument, with the unit in the column heading.
- A graph that is a straight line through the origin shows direct proportionality.
- Repeating readings reduces random errors but not systematic errors such as a zero error.
Common mistakes
- Writing “keep everything else constant” instead of naming the control variables.
- Recording more digits than the instrument can give.
- Joining plotted points dot to dot instead of drawing a best-fit line.
- Calling any rising straight line “directly proportional”.
- Writing “human error” or “repeat the experiment” as an improvement without naming the error it fixes.