• 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 thermometer / a stopwatch or timer / weighing scales / a measuring jug or cylinder) → 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 heavy a pet hamster is / how much water a plant is given / how cold the water in a pond is / how long it takes to run 50 metres) → how heavy a pet hamster isPrompt: What does this tool measure: length, temperature, mass, time or volume?
3. Which tool would show that the water in a bowl is getting colder? (a thermometer / a measuring jug / a magnifying glass / a ruler) → a thermometerPrompt: Colder means the temperature is going down.

• 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. 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. 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. Isla tests which ball bounces highest. She drops one ball from 1 m and another from 2 m. What is wrong? (Nothing, it is fair / She should not measure the bounce / The drop height should be the same / She should use only one ball) → The drop height should be the samePrompt: What is she trying to compare?
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? (the note he hears / nothing else matters / how tight and thick the strings are / the length of the strings) → how tight and thick the strings arePrompt: Tightness and thickness also change the note.

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