* Physical properties are characteristics of a substance that can be observed or measured without changing the substance's chemical composition. Examples include color, odor, density, melting point, and boiling point.
* Chemical properties describe how a substance reacts with other substances or how it changes its chemical composition. Examples include flammability, reactivity with acids, and the ability to rust.
Since the colorlessness of neon gas doesn't involve any chemical change, it's a physical property.
