• Quick retrieval from earlier learning (Choosing a measuring tool). Students answer on mini whiteboards.
• Show answers together and note who needs support in the main task.

1. Which tool would you use to measure how heavy an apple is? (weighing scales / a stopwatch or timer / a measuring jug or cylinder / a thermometer) → weighing scalesPrompt: Is it a length, a temperature, a mass, a time or an amount of liquid?
2. What could you measure with a stopwatch or timer? (the mass of a bag of flour / how far a paper plane flew / how long it takes to run 50 metres / how warm the classroom is) → how long it takes to run 50 metresPrompt: What does this tool measure: length, temperature, mass, time or volume?
3. Kofi wants to find out which ball bounces highest. Which tool helps most? (weighing scales / a thermometer / a metre stick (long ruler) / a measuring jug) → a metre stick (long ruler)Prompt: Bounce height is a length.

• Show a simple experiment with one thing changed and ask what makes it a fair test.
• Share the objective: Planning a fair test. Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: Leo tests which paper towel soaks up the most water. What should he change?
• Step 1: He is testing types of paper towel, so that is the only thing he changes.
• Step 2: So the answer is: the type of paper towel
• Answer: the type of paper towel
• 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. Why is it a good idea to repeat a test several times? (To change the answer / To make the test unfair / Because the first try never counts / To check the results are reliable) → To check the results are reliablePrompt: What if one result was a mistake?
2. Which question can be answered with a fair test? (Is a rainbow beautiful? / Does a heavier parachute fall faster? / What is your favourite plant? / Who is the best scientist?) → Does a heavier parachute fall faster?Prompt: A fair test changes one thing and measures another.

• 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. Omar tests how the length of a guitar string changes its note. He uses strings of different lengths. What else should stay the same? (nothing else matters / the length of the strings / the note he hears / how tight and thick the strings are) → how tight and thick the strings arePrompt: Tightness and thickness also change the note.
2. Mateo wants to know if plants grow better with more light. Which plan is fair? (Different plants, different water, different light / More water for the plant in the light / Same light for every plant / Same plant type, same water, different amounts of light) → Same plant type, same water, different amounts of lightPrompt: Only the thing being tested should change.

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-3.