• 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 much juice is in a carton? (a ruler or tape measure / a thermometer / a measuring jug or cylinder / weighing scales) → a measuring jug or cylinderPrompt: 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 cold the water in a pond is / how heavy an apple is / how much milk is in a glass / how warm the classroom is) → how much milk is in a glassPrompt: 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. Mateo wants to know if plants grow better with more light. Which plan is fair? (Different plants, different water, different light / Same light for every plant / More water for the plant in the light / Same plant type, same water, different amounts of light) → 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 time for the sugar to dissolve / the temperature of the water / the colour of the sugar) → 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. Fair tests: which statement is true? (If a result surprises you, you should hide it. / One try is always enough. / You should change as many things as possible. / In a fair test you change only one thing.) → In a fair test you change only one thing.Prompt: Think about what makes a test fair.
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 / the length of the strings / how tight and thick the strings are / nothing else matters) → 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.