Frame the lesson clearly: "Today you plan and run your own fair test — this is assessed." Connect the two threads students have built: the fair-test planning from Lesson 1 and the foil-conducts-electricity result from Lesson 11.
Pose the investigation context: a foil ribbon can carry electricity in a circuit, but does changing the foil change how well the circuit works? Model turning that into a testable question, thinking aloud through the three variable roles:
Model a reasoned prediction: "I predict a longer foil ribbon will make the globe dimmer, because the electricity has further to travel." Emphasise the "...because..." and remind students how to record method and safety.
Co-plan one example investigation on the board using the planner structure, then hand the planning to the groups. Together, fill in:
- Testable question: "Does the length of the foil ribbon affect how brightly the globe glows?"
- Variable to change / to measure / to control;
- Prediction with reasoning;
- Method steps and one safety note.
Show how to record results in a simple table (foil length vs brightness rating or lights/doesn't light). Stress measuring brightness consistently (e.g. a 0–3 scale) so results are comparable.
Groups complete the Foil circuit investigation planner and, once their plan is approved, run the test:
- write the testable question and identify the change / measure / control variables;
- record a reasoned prediction and the method, with a safety note;
- get the plan approved by the teacher before connecting anything;
- build the circuit, change only the chosen variable, and record results in the table.
Circulate to approve plans and check tests stay fair. Keep each group's planner and results — they are the assessment evidence and feed into Lessons 13–14.
Close: each group states their result in one sentence and whether it matched their prediction.