# Materials Concept Cartoon

This cartoon was developed to assess students’ beginning understanding of density as an intrinsic property of different materials. Students have previously investigated 8 cubes that have identical volumes, compared their weights, their properties such as color, and observed that when cubes are cut in half they look the same inside and out and are solid all the way through. This concept cartoon shows if students can use these experiences as evidence to evaluate different proposed explanations of the weight differences of the cubes. It is typically used after Investigating Materials 4, How can we sort cubes that are all the same size?.

## Things to look for in student responses

### Sam:

Sam explains that the pine cube is lighter because it is hollow, an idea initially appealing to many students because of everyday experiences with solid looking objects that are very light because they are hollow inside (e.g., boxes, soup cans). Can students see that this idea can’t explain the weight differences of the density cubes, because they have observed a pine cube cut in half first–hand and found that it is solid all the way through?

### Jose:

Jose posits that the difference is due to an intrinsic difference in materials themselves (pine is a lighter kind of material than copper). Do students agree with Jose, noting that this explanation is consistent with what they have observed about the cubes?

### Napoleon:

Napoleon thinks the cubes may be hollow and filled with objects of different weights, a variant on Sam’s idea that is also appealing to students based on their everyday experiences. Can students use their prior experiences with the cubes to argue against this idea, noting that the pine is pine “all the way through” and the copper is copper “all the way through.”