• 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 measuring jug or cylinder / 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 heavy an apple is / how much juice is in a carton / how warm the classroom is) → how heavy an apple isPrompt: 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? (a measuring jug / a metre stick (long ruler) / weighing scales / a thermometer) → 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. 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.
2. Aisha measures how fast sugar dissolves in water at different temperatures. What does she measure? (the colour of the sugar / the temperature of the water / 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 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. 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 / She should not measure the bounce / The drop height should be the same) → The drop height should be the samePrompt: What is she trying to compare?
2. Which question can be answered with a fair test? (What is your favourite plant? / Who is the best scientist? / Is a rainbow beautiful? / Does a heavier parachute fall faster?) → Does a heavier parachute fall faster?Prompt: A fair test changes one thing and measures another.

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