Scientific Inquiry and Practical Skills
Scientific Inquiry and Practical Skills
This domain tests how you plan fair investigations, choose and use instruments, record data, analyse results and work safely. Questions may describe a practical setup and ask for variables, a control, a risk assessment or a conclusion.
Core rules and concepts
- A fair test changes one independent variable, measures one dependent variable, and keeps all other variables constant. A control is a comparison treatment without the active factor; a control variable is held constant.
- Hypotheses must be testable. Predictions follow from hypotheses. Repeat readings and calculate a mean to reduce random error; check for zero error and parallax to reduce systematic error.
- Measurement: use SI units (m, kg, s, K, A, mol, cd). Read a measuring cylinder at the bottom of the meniscus at eye level. Record to the precision of the instrument and include the unit.
- Safety: identify hazards, assess risk, and use controls - goggles, fuses, sand bucket, fume cupboard, heatproof mat, hand washing. Never taste chemicals or point a test tube at anyone.
Worked example
A learner investigates the effect of light intensity on photosynthesis by counting oxygen bubbles from pondweed. Identify the variables and a flaw. Independent variable: light intensity (lamp distance). Dependent variable: bubble rate (count per minute). Controlled: temperature, carbon dioxide concentration, pondweed length, water. Flaw: changing lamp distance also changes temperature, so temperature is confounded with light. Improve by using a heat filter or water bath and repeating at each distance. Reasoning: a fair test requires that only light intensity differs; otherwise the result cannot be attributed to light.
Traps that cost marks
Calling any hands-on activity an inquiry; confusing accuracy with precision; reading a meniscus at the top; forgetting units or significant figures; failing to identify a hazard; treating a correlation as proof of cause; using a control group but not controlling variables.