Here's why:

* Chemical property: A chemical property describes how a substance reacts or changes its composition when interacting with other substances or under specific conditions.

* Density: Density is a measure of mass per unit volume. It's an intrinsic property of a substance, meaning it's constant for a given substance under specific conditions (like temperature and pressure).

While density is often used in physical calculations, it's directly related to a substance's molecular structure and composition. For example:

* Different densities of water and oil: Water molecules are more tightly packed than oil molecules, leading to a higher density for water. This difference in density causes oil to float on water.

* Density changes in chemical reactions: If a chemical reaction creates a new substance with a different molecular structure, its density will also change.

Therefore, density is a chemical property because it's a characteristic that is determined by the substance's chemical composition and molecular structure.