Density Curriculum

Section 2—Lesson 5: Why Is Density Considered a Property of a Particular Kind of Matter?

Understanding Goals

Subject Matter

• Density is not affected by the size or shape of the object.
• The density of a certain substance or kind of matter does not change if the amount of matter in a given object changes. You can have more or less matter without affecting density, as long as the substance stays the same.
• Specific densities are assigned to specific elements. These are numbers that define the density of the elements under standard conditions of temperature and pressure.
• The density of a substance can be used to help identify that substance.

Causality

• Because density is determined by a relationship, if you cut an object in half so that you have less volume, you also have less mass, so the relationship—the density—stays the same.
• One of the reasons that it is hard to realize that cutting an object in half doesn't change its density is that we forget to focus on the relationship between mass and volume and instead focus on either mass or volume.