Here's why:
* Density is defined as the mass of a substance per unit volume. This means it tells you how much matter is packed into a given space.
* Higher density means more matter is packed into the same space, making the substance more concentrated.
* Lower density means less matter is packed into the same space, making the substance less concentrated.
For example:
* Lead is a very dense material, meaning it has a lot of mass packed into a small volume.
* Air is a less dense material, meaning it has less mass packed into the same volume.
Therefore, density is the key physical property that describes the concentration of matter.
