* Physical properties are characteristics of a substance that can be observed or measured without changing the substance's chemical composition. Melting point is a direct result of the substance's internal structure and forces between atoms, not a change in its chemical makeup.
* Chemical properties describe how a substance reacts with other substances or how it changes its chemical composition.
In summary: Melting sodium at 98°C changes its state of matter (solid to liquid) but doesn't change its chemical formula (Na).
