• Quick retrieval from earlier learning (Evaluating experiments (research summaries)). Students answer on mini whiteboards.
• Show answers together and note who needs support in the main task.

1. Experiment 1: Seeds were kept at 10 °C, 20 °C and 30 °C, all watered daily, and the number that germinated was counted. Experiment 2: Seeds were kept at 20 °C and given 0, 5 or 10 mL of water a day. In Experiment 2, which variable was changed on purpose? (the temperature / the colour of the pots / the volume of water / the number of seeds that germinated) → the volume of waterPrompt: Look only at the description of Experiment 2.
2. Experiment 1: Seeds were kept at 10 °C, 20 °C and 30 °C, all watered daily, and the number that germinated was counted. Experiment 2: Seeds were kept at 20 °C and given 0, 5 or 10 mL of water a day. Which variable was kept constant in Experiment 2 but changed in Experiment 1? (the number of seeds that germinated / the colour of the pots / the temperature / the volume of water) → the temperaturePrompt: What was tested in Experiment 1?
3. Hypothesis: "Plants grow faster in blue light than in red light." Which experiment tests it best? (Plants in blue light only / Different species under the same lamp / One plant in blue light outdoors and one in red light indoors / Identical plants under blue or red lamps of equal brightness, same water and temperature) → Identical plants under blue or red lamps of equal brightness, same water and temperaturePrompt: Only the colour of light should differ.

• Show a simple experiment with one thing changed and ask what makes it a fair test.
• Share the objective: Comparing scientific explanations (conflicting viewpoints). Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: Two students explain why a ball rolling on a flat floor eventually stops. Student 1: Objects naturally slow down and stop when nothing keeps pushing them. Student 2: Friction and air resistance act against the motion; with no resistive forces, the ball would keep moving at a steady speed. Which student's view agrees with Newton's first law?
• Step 1: Newton's first law: an object keeps moving at constant velocity unless a resultant force acts.
• Step 2: So the answer is: Student 2
• Answer: Student 2
• 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. What makes a scientific explanation stronger than another? (It explains more of the evidence and makes predictions that are confirmed / It is older / It is more complicated / More people like it) → It explains more of the evidence and makes predictions that are confirmedPrompt: Scientists judge ideas by evidence.
2. Two scientists explain why the Moon shows phases. Scientist 1: Earth's shadow covers different amounts of the Moon during the month. Scientist 2: Half of the Moon is always lit by the Sun; as the Moon orbits Earth, we see different amounts of the lit half. Which scientist's explanation is accepted by astronomers today? (neither / Scientist 2 / both / Scientist 1) → Scientist 2Prompt: Read each viewpoint and underline its key claim.

• 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. Two scientists explain why some lakes have fewer fish than ten years ago. Scientist 1: Farm fertiliser washed into the lakes caused algae to grow; when the algae died, bacteria used up the oxygen in the water. Scientist 2: Warmer water from climate change holds less dissolved oxygen, so fewer fish survive. A lake far from any farm also lost fish as it warmed. This supports… (neither scientist / Scientist 1 / Scientist 2 / only that fertiliser is harmless) → Scientist 2Prompt: Read each viewpoint and underline its key claim.
2. A new observation contradicts a well-tested theory. What usually happens? (Science stops / The observation is always thrown away / Scientists check the observation, then improve or replace the theory if it holds up / The theory is never changed) → Scientists check the observation, then improve or replace the theory if it holds upPrompt: Science changes when evidence changes.

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