• 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 measuring jug or cylinder / a ruler or tape measure / weighing scales / a stopwatch or timer) → 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 cold the water in a pond is / how long a toy car takes to roll down a ramp / the mass of a pumpkin / how much milk is in a glass) → the mass of a pumpkinPrompt: 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 stopwatch / a thermometer / a ruler / 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. Why is it a good idea to repeat a test several times? (Because the first try never counts / To make the test unfair / To check the results are reliable / To change the answer) → To check the results are reliablePrompt: What if one result was a mistake?
2. Aisha measures how fast sugar dissolves in water at different temperatures. What does she measure? (the temperature of the water / the colour of the sugar / the type of cup / the time for the sugar to dissolve) → the time for the sugar to dissolvePrompt: She changes the temperature. What does she then look at?

• 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 fair test means everyone gets a turn. / One try is always enough. / You should change as many things as possible. / 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. Mateo wants to know if plants grow better with more light. Which plan is fair? (Same plant type, same water, different amounts of light / 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 lightPrompt: Only the thing being tested should change.

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