Investigating Volume 3:

Does changing the shape of an object change its volume?

Plan Investigating Volume 3

What if you had a bucket of sand, and you made a sandcastle with it. What would happen if you scooped up all that sand and made a sand dragon instead? Would the dragon have the same volume as the castle?

In this investigation, students grapple with the idea that volume can remain constant when an object changes its shape. First they arrange eight wooden cubes into different shapes and determine that the volumes of the different objects are the same. Then they repeat the activity using plastic modeling clay.

As they squeeze and poke the plastic modeling clay into irregular shapes — and can no longer count the cubes — they are left to wonder: Same volume or different?

Learning Goals

  • to consider whether changing the shape of an object also changes its volume
Sequence of experiences
1. Ask the question Small Groups 15 Mins
2. Explore shape and volume with wooden cubes Small Groups 10 Mins
3. Explore shape and volume with plastic modeling clay cubes Small Groups 20 Mins
4. Make meaning All Class 10 Mins

Materials and Preparation

For the class:
  • Post the investigation question in a place where all students can see it
  • Class volume line from the previous sessions
For each student:
  • 1 plastic knife
  • 1 small plate
  • 8 centimeter cubes
  • Approximately 10 cubic centimeters of plastic modeling clay

Concept Cartoon

Darwin from the Concept Cartoons

The Volume Concept Cartoon is typically used as a formative assessment at the end of this investigation.

Formative Assessment
Formative Assessment icon

Do students understand that the volume of 8cc of plastic modeling clay stays the same even if you change the shape?

Listen to the students' discussion of their new 8cc plastic modeling clay shapes as evidence of their current understanding of volume. Joan listens for these ideas as she interprets their responses to her questions. Note that all the sculptures on Joan's tray have the same 8cc volume.

  • The volume is the same even if you change the shape, because you haven't added any plastic modeling clay or taken any away.
  • Even though the shapes look different, the volume of the plastic modeling clay is still the same - 8 ccs.
  • The volumes are not the same because the new shape looks like it takes up more space (inaccurate).

As a next step, Joan shows a tray holding all of the 8cc objects and asks, "If I made a volume line, where would we put each of these objects?"