• 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 the width of a leaf? (a ruler or tape measure / weighing scales / a thermometer / 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 a stopwatch or timer? (how long a worm is / how tall a sunflower has grown / how cold the water in a pond is / how long a toy car takes to roll down a ramp) → how long a toy car takes to roll down a rampPrompt: What does this tool measure: length, temperature, mass, time or volume?
3. Which is the best tool to find out how long it takes a snail to cross a table? (a thermometer / a ruler / a stopwatch / a rain gauge) → a stopwatchPrompt: "How long it takes" is about time.

• 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. Leo tests which paper towel soaks up the most water. What should he change? (the size of the towel / the amount of water / the time he waits / the type of paper towel) → the type of paper towelPrompt: In a fair test you change only one thing: the thing you are testing.
2. Which question can be answered with a fair test? (What is your favourite plant? / Is a rainbow beautiful? / Does a heavier parachute fall faster? / 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 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. Leo tests which paper towel soaks up the most water. What should he change? (the size of the towel / the amount of water / the time he waits / the type of paper towel) → the type of paper towelPrompt: In a fair test you change only one thing: the thing you are testing.
2. Fair tests: which statement is true? (A fair test means everyone gets a turn. / You should change as many things as possible. / You should keep everything else the same. / If a result surprises you, you should hide it.) → You should keep everything else the same.Prompt: Think about what makes a test fair.

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