• 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 heavy a pet hamster is? (a stopwatch or timer / weighing scales / a measuring jug or cylinder / a thermometer) → weighing scalesPrompt: 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 rainwater was collected / how much juice is in a carton / how far a paper plane flew / the mass of a bag of flour) → the mass of a bag of flourPrompt: 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 thermometer / a metre stick (long ruler) / weighing scales / a measuring jug) → 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. Leo tests which paper towel soaks up the most water. What should he change? (the time he waits / the type of paper towel / the amount of water / the size of the towel) → the type of paper towelPrompt: In a fair test you change only one thing: the thing you are testing.
2. Aisha measures how fast sugar dissolves in water at different temperatures. What does she measure? (the type of cup / the colour of the sugar / the time for the sugar to dissolve / the temperature of the water) → 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. Mateo wants to know if plants grow better with more light. Which plan is fair? (More water for the plant in the light / Same light for every plant / Same plant type, same water, different amounts of light / Different plants, different water, different light) → Same plant type, same water, different amounts of lightPrompt: Only the thing being tested should change.
2. Fair tests: which statement is true? (You should change as many things as possible. / A fair test means everyone gets a turn. / One try is always enough. / A prediction says what you think will happen.) → A prediction says what you think will happen.Prompt: Think about what makes a test fair.

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