• 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 an apple is? (a ruler or tape measure / a stopwatch or timer / a thermometer / weighing scales) → weighing scalesPrompt: Is it a length, a temperature, a mass, a time or an amount of liquid?
2. What could you measure with a thermometer? (how hot a cup of tea is / how long a toy car takes to roll down a ramp / the mass of a pumpkin / how much rainwater was collected) → how hot a cup of tea isPrompt: 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? (weighing scales / a ruler / a stopwatch / a thermometer) → 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. Mateo wants to know if plants grow better with more light. Which plan is fair? (Different plants, different water, different light / More water for the plant in the light / Same plant type, same water, different amounts of 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 type of cup / the temperature of the water / the colour of the sugar / 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. Which question can be answered with a fair test? (Does a heavier parachute fall faster? / What is your favourite plant? / Is a rainbow beautiful? / Who is the best scientist?) → Does a heavier parachute fall faster?Prompt: A fair test changes one thing and measures another.
2. Why is it a good idea to repeat a test several times? (Because the first try never counts / To check the results are reliable / To make the test unfair / To change the answer) → To check the results are reliablePrompt: What if one result was a mistake?

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