The same pieces, a different object

Can a bridge become a tower without gaining or losing pieces?

Submit: Three-stage inventory and an evidence-based account of the reconstruction.

Related lesson: Changes in Matter

This is a teacher-led extension beyond the short lesson. The task supplies a performance opportunity; completion alone does not certify mastery, full NGSS coverage or state alignment.

Build the idea

An object can be made of smaller pieces. The arrangement gives the whole object a shape and a use. Taking it apart and arranging the same pieces differently can create a new object. Observing the pieces before and after helps us explain what changed and what stayed the same.

Evidence and model inputs

Example inventory: six long blocks, four short blocks and two flat blocks make a bridge. After disassembly, the same inventory makes a tower. This is a planning example; use the actual set provided and make an inventory that matches it.

Keep actual observations, published findings and invented model cases labeled separately. If a source or required equipment is unavailable, pause that part with a teacher; do not invent results.

Materials and preparation

Large interlocking blocks or construction pieces, tray, paper or camera. Use pieces appropriate to the child’s age.

Grade-level scope

Observe disassembly and reassembly; do not substitute an unsupported abstract conservation statement for observations.

Do the work

1. Sort a safe set of large building pieces by visible type and draw an inventory.
2. Build an object and describe its purpose. Photograph or sketch it.
3. Take the object apart into a tray. Check that the inventory still matches.
4. Build a different object using the same pieces, with no pieces added or discarded.
5. Explain how the new arrangement changes the object while the component set remains the same.

Learner worksheet

Write on paper or type here and print. Entries stay in this page’s memory and are lost when you leave or reload; they are not saved or submitted.

Check your reasoning

1. What changes when the bridge becomes a tower?
2. What stays the same in this task?
3. How can you support that claim?
4. Does building a new shape create new material?

Teacher review guide

Review the actual deliverable and discuss the reasoning. For each criterion, use 0 when evidence is absent or fundamentally incorrect, 1 when partly supported with a material error or omission, and 2 when accurate, supported and complete for the stated task. Maximum 8 points is a task score, not a proficiency certification. Give feedback and allow revision.

1. Records the original component set.
2. Builds, disassembles and rebuilds two distinct objects.
3. Uses observations to track the same pieces throughout.
4. Explains arrangement versus material identity.

Sources and standard reference

• Official NGSS 2-PS1-3 performance expectation — inspect the practice, core idea, crosscutting concept and assessment boundary.

Instructional text and hypothetical cases are original. Linked source readings supply published evidence where specified. Teachers should judge fit with their course and state requirements.