Here's why:

* Physical properties are characteristics of a substance that can be observed or measured without changing the substance's chemical composition.

* Chemical properties describe how a substance reacts with other substances or changes its chemical composition.

Luster describes how light reflects off the surface of a material. It doesn't involve any chemical change. For example, gold is shiny (lustrous) whether it's in a nugget or a thin sheet. Its chemical composition remains the same.

Here are some examples of physical properties:

* Color

* Density

* Melting point

* Boiling point

* Hardness

Here are some examples of chemical properties:

* Flammability

* Reactivity with acids

* Oxidation