• 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 rainwater was collected? (weighing scales / a thermometer / a ruler or tape measure / a measuring jug or cylinder) → 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 stopwatch or timer? (how much rainwater was collected / how long an ice cube takes to melt / how much milk is in a glass / how long a worm is) → how long an ice cube takes to meltPrompt: 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 magnifying glass / a ruler / a thermometer / a measuring jug) → 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. Leo tests which paper towel soaks up the most water. What should he change? (the size of the towel / the type of paper towel / the time he waits / the amount of water) → 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 time for the sugar to dissolve / the temperature of the water / the type of cup / 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? (You should keep everything else the same. / If a result surprises you, you should hide it. / One try is always enough. / A fair test means everyone gets a turn.) → You should keep everything else the same.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 / nothing else matters / how tight and thick the strings are) → 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.