• 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 long a toy car takes to roll down a ramp? (a stopwatch or timer / weighing scales / a thermometer / a ruler or tape measure) → a stopwatch or timerPrompt: Is it a length, a temperature, a mass, a time or an amount of liquid?
2. What could you measure with a measuring jug or cylinder? (how hot a cup of tea is / how warm the classroom is / how much water a plant is given / how long it takes to run 50 metres) → how much water a plant is givenPrompt: 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 stopwatch / a ruler / 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. Mateo wants to know if plants grow better with more light. Which plan is fair? (Same plant type, same water, different amounts of light / More water for the plant in the light / Different plants, different water, different light / Same light for every plant) → Same plant type, same water, different amounts of lightPrompt: Only the thing being tested should change.
2. Omar tests how the length of a guitar string changes its note. He uses strings of different lengths. What else should stay the same? (how tight and thick the strings are / the length of the strings / the note he hears / nothing else matters) → how tight and thick the strings arePrompt: Tightness and thickness also change the note.

• 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. Priya tests which surface a toy car rolls furthest on. What must she keep the same? (the type of surface / nothing / how far the car rolls / the height of the ramp) → the height of the rampPrompt: Only the surface should change.
2. Fair tests: which statement is true? (One try is always enough. / In a fair test you change only one thing. / If a result surprises you, you should hide it. / A fair test means everyone gets a turn.) → In a fair test you change only one thing.Prompt: Think about what makes a test fair.

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