Density Curriculum

Section 1—Lesson 1: How Can Objects of the Same Volume Differ in Mass?

Understanding Goals

Objects that are made of different materials can have the same mass and different volumes, or the same volumes but different mass. This is because of a property called "density."
All matter has density.
We can come up with different models for visualizing density.
One way to think about density that students often find helpful is to think about how crowded or packed a material is. Many models use various illustrations of crowdedness (or more or less packed in) as a way of conveying density.
Denser things are more crowded or more tightly packed.

Density is non-obvious. You can only detect differences in density by controlling for mass or for volume.
You can't measure the density of an object directly. You can only figure it out by knowing the relationship between its mass and its volume.
When we are looking for the causes, we often focus on only obvious ones because they are easiest to notice.
People often miss the role that density plays in the real world. Instead, they make the mistake of thinking only about mass or volume.