Does changing the shape of an object change its volume?
1. Ask the question
Drawing attention to the objects arrayed on the class volume line:
- How is volume different from shape?
It’s a tricky distinction, and students may struggle with it. What responses do they have? Encourage different formulations until you reach a consensus like this:
- Shape describes what an object looks like, or how it is arranged. Volume describes how much space it takes up.
Check for understanding:
- Can two objects have the same shape but have different volumes?
- Yes, for example a small cube and a large cube.
Once the class is clear about the distinction between shape and volume, introduce the investigation question:
What about compressible materials? This investigation deals with incompressible materials like wooden blocks. Simply rearranging the blocks into different shapes will not change their volumes. Compressible materials behave differently. For example, when you squeeze a slice of Wonder Bread, it loses volume.
Help them with the inquiry by presenting some scenarios:
- Say you made a robot out of 300 Lego pieces. What if you took the robot apart and made a spaceship instead, using all the Legos. Do you think the robot and the spaceship have different volumes?
- What if you and your best friend each have a liter of milk. If you pour all your milk into a big jar, and your friend pours all his milk into 16 glasses, who has more milk?
- Say you had a wall made of bricks. If you tore it down and built a whole different wall, using all the same bricks, would the new wall have the same volume as the old wall? Let’s find out.
