• 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 wooden table / a curtain / a drinking glass / a jam jar) → a wooden tablePrompt: 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 paperclip / a cricket or baseball bat / a garden fence / a wooden table) → a paperclipPrompt: Name the usual material of each object.
3. Why are cricket and baseball bats often made of wood rather than glass? (Glass is too bendy. / Glass is too light. / Wood is tough and will not shatter when it hits a ball. / Wood is see-through.) → 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. Hana builds a house from 14 building bricks, then takes it apart and uses every brick to build a bridge. How many bricks are in the new model? → 14Prompt: Were any bricks added or lost?
2. A model castle is made of 6 wooden blocks. Each block has a mass of 20 g. The castle is taken apart and rebuilt as a boat with all the same blocks. What is the mass of the boat? → 120 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. Hiro builds a car from 14 building bricks, then takes it apart and uses every brick to build a house. How many bricks are in the new model? → 14Prompt: Were any bricks added or lost?
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.