• Quick retrieval from earlier learning (Alpha, beta and gamma radiation). Students answer on mini whiteboards.
• Show answers together and note who needs support in the main task.

1. Which type of radiation: an electromagnetic wave? (alpha (α) / beta (β) / gamma (γ)) → gamma (γ)Prompt: The more ionising the radiation, the less penetrating it is.
2. Smoke detectors contain a source that emits alpha particles. Why alpha? (Alpha passes through walls / Alpha ionises the air strongly but is stopped by smoke and cannot leave the detector / Alpha is an electromagnetic wave / Alpha has the longest range) → Alpha ionises the air strongly but is stopped by smoke and cannot leave the detectorPrompt: Smoke blocks the particles, changing the current.
3. Nuclear radiation: which statement is NOT true? (Beta particles are helium nuclei. / Radioactive decay is random. / Background radiation comes from natural and man-made sources. / Gamma rays are part of the electromagnetic spectrum.) → Beta particles are helium nuclei.Prompt: Which radiation needs lead to stop it?

• Show the periodic table and ask what patterns students can see before anything is explained.
• Share the objective: Nuclear fission and fusion. Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: Fission or fusion: used in today's nuclear power stations?
• Step 1: Fission splits a large nucleus into two smaller ones, releasing neutrons and energy.
• Step 2: So the answer is: fission
• Answer: fission
• Pause after each step and ask a student to say what comes next.

• Do these together. Students try each step on whiteboards before you reveal it.
• Use the hints as prompts rather than giving the answer.

1. Fission or fusion: needs extremely high temperature and pressure? (fission / fusion) → fusionPrompt: Fission splits; fusion joins.
2. What starts a chain reaction in uranium-235? (gamma rays splitting protons / electrons jumping between atoms / neutrons released by one fission go on to cause more fissions / heat melting the fuel) → neutrons released by one fission go on to cause more fissionsPrompt: Each fission releases two or three neutrons.

• Students work on the student sheet. Circulate and check the first two answers of every student early.
• Students who finish: write a question of their own for a partner, with the answer.

The 8 questions are on the student sheet below, with answers in the key.

• Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

1. Fission and fusion: which statement is NOT true? (Fission products are usually radioactive. / Fusion releases energy in the Sun. / A nuclear reactor uses a moderator to slow neutrons down. / Today's nuclear power stations use fusion.) → Today's nuclear power stations use fusion.Prompt: Which process do working power stations use?
2. In 2022 a US laser facility (the National Ignition Facility) reported a fusion milestone. What was it? (more fusion energy came out of the fuel than the laser energy delivered to it / uranium was fused into gold / fusion was achieved at room temperature / a fusion power station started supplying homes) → more fusion energy came out of the fuel than the laser energy delivered to itPrompt: It was a scientific gain, not yet electricity for the grid.

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-11.