• Quick retrieval from earlier learning (One material, many objects; one object, many materials). Students answer on mini whiteboards.
• Show answers together and note who needs support in the main task.

1. Which of these is usually made of wood? (a pillowcase / a curtain / a cricket or baseball bat / a drinking glass) → a cricket or baseball batPrompt: Think about how each object feels and what it needs to do.
2. Three of these are usually made of wood. Which one is NOT? (a pencil / a cricket or baseball bat / a garden fence / a pillowcase) → a pillowcasePrompt: Name the usual material of each object.
3. Why are cricket and baseball bats often made of wood rather than glass? (Wood is tough and will not shatter when it hits a ball. / Wood is see-through. / Glass is too bendy. / Glass is too light.) → Wood is tough and will not shatter when it hits a ball.Prompt: What happens to glass when it is hit hard?

• Pass round objects made of different materials and ask why each one was chosen.
• Share the objective: Build, take apart and rebuild with the same pieces. Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: Ben builds a house from 32 building bricks, then takes it apart and uses every brick to build a bridge. How many bricks are in the new model?
• Step 1: The same pieces are just arranged differently.
• Step 2: So the answer is: 32
• Answer: 32
• 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. Ava builds a tower from 22 building bricks, then takes it apart and uses every brick to build a bridge. How many bricks are in the new model? → 22Prompt: Were any bricks added or lost?
2. A model castle is made of 8 wooden blocks. Each block has a mass of 10 g. The castle is taken apart and rebuilt as a boat with all the same blocks. What is the mass of the boat? → 80 gPrompt: Does changing the shape change how much material there is?

• 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 6 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. A model castle is made of 15 wooden blocks. Each block has a mass of 5 g. The castle is taken apart and rebuilt as a boat with all the same blocks. What is the mass of the boat? → 75 gPrompt: Does changing the shape change how much material there is?
2. A puzzle is broken up into 100 pieces and put back together. Which is TRUE? (It has the same pieces and the same mass as before. / It has more pieces. / It is made of a new material. / It is now heavier.) → It has the same pieces and the same mass as before.Prompt: Nothing was added or taken away.

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-2.