• 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: stopped by a few mm of aluminium? (alpha (α) / beta (β) / gamma (γ)) → beta (β)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 has the longest range / Alpha is an electromagnetic wave) → 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? (Gamma rays are part of the electromagnetic spectrum. / Background radiation comes from natural and man-made sources. / We can predict exactly when a particular nucleus will decay. / Alpha radiation is the most dangerous if the source is inside the body.) → We can predict exactly when a particular nucleus will decay.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: used in today's nuclear power stations? (fission / fusion) → fissionPrompt: Fission splits; fusion joins.
2. What starts a chain reaction in uranium-235? (electrons jumping between atoms / neutrons released by one fission go on to cause more fissions / heat melting the fuel / gamma rays splitting protons) → 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 6 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? (Fusion releases energy in the Sun. / Fusion splits large nuclei. / A nuclear reactor uses a moderator to slow neutrons down. / Fission products are usually radioactive.) → Fusion splits large nuclei.Prompt: Which process do working power stations use?
2. Why is fusion so hard to achieve on Earth? (Fusion only works with uranium / Fusion releases no energy / There is no hydrogen on Earth / Nuclei repel each other, so extremely high temperatures and pressures are needed) → Nuclei repel each other, so extremely high temperatures and pressures are neededPrompt: Both nuclei are positively charged.

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