• 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 tall a sunflower has grown? (a stopwatch or timer / weighing scales / a ruler or tape measure / a measuring jug or cylinder) → a ruler or tape measurePrompt: Is it a length, a temperature, a mass, a time or an amount of liquid?
2. What could you measure with weighing scales? (how much water a plant is given / how heavy an apple is / how much juice is in a carton / how long it takes to run 50 metres) → how heavy an apple isPrompt: What does this tool measure: length, temperature, mass, time or volume?
3. Zara wants to know if her bean plant grows taller each day. What should she use? (weighing scales / a thermometer / a stopwatch / a ruler) → a rulerPrompt: She wants to know how tall it is.

• 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. Isla tests which ball bounces highest. She drops one ball from 1 m and another from 2 m. What is wrong? (She should use only one ball / The drop height should be the same / Nothing, it is fair / She should not measure the bounce) → The drop height should be the samePrompt: What is she trying to compare?
2. Ben tests whether salt water or tap water freezes faster. Which must he keep the same? (the time each one takes to freeze / whether the water has salt / the type of water / the volume of water in each cup) → the volume of water in each cupPrompt: He is changing the type of water and measuring the time.

• 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. Fair tests: which statement is true? (A prediction says what you think will happen. / If a result surprises you, you should hide it. / A fair test means everyone gets a turn. / One try is always enough.) → A prediction says what you think will happen.Prompt: Think about what makes a test fair.
2. Leo tests which paper towel soaks up the most water. What should he change? (the size of the towel / the time he waits / the amount of water / the type of paper towel) → the type of paper towelPrompt: In a fair test you change only one thing: the thing you are testing.

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