• 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 hot a cup of tea is? (a stopwatch or timer / a thermometer / a ruler or tape measure / a measuring jug or cylinder) → a thermometerPrompt: 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? (how much milk is in a glass / how long a worm is / how tall a sunflower has grown / how long an ice cube takes to melt) → how long an ice cube takes to meltPrompt: 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? (a ruler / a thermometer / a stopwatch / weighing scales) → 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 / Nothing, it is fair / The drop height should be the same / She should not measure the bounce) → The drop height should be the samePrompt: What is she trying to compare?
2. Omar tests how the length of a guitar string changes its note. He uses strings of different lengths. What else should stay the same? (how tight and thick the strings are / the note he hears / the length of the strings / nothing else matters) → how tight and thick the strings arePrompt: Tightness and thickness also change the note.

• 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. Fair tests: which statement is true? (You should change as many things as possible. / One try is always enough. / If a result surprises you, you should hide it. / Repeating a test helps you check your results.) → Repeating a test helps you check your results.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 amount of water / the type of paper towel / the time he waits) → 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.