* Chemical Change: A chemical change involves the formation of new substances with different chemical properties.

* Physical Change: A physical change alters the form or appearance of a substance, but not its chemical composition.

What Happens When You Heat NaCl:

* Melting: NaCl has a high melting point (801°C). When you heat it, you're providing enough energy to overcome the attractive forces between the ions, causing it to melt into a liquid state. The chemical composition (NaCl) remains the same.

* Sublimation (at higher temperatures): At even higher temperatures, NaCl can sublimate directly from a solid to a gas. Again, the chemical composition remains unchanged.

No New Substance is Formed:

The heating of NaCl does not break the ionic bonds between the sodium (Na+) and chloride (Cl-) ions. The ions are simply rearranged, leading to a change in physical state (solid to liquid to gas), but not a change in the chemical formula.

Conclusion:

Heating sodium chloride is a physical change as it only affects the state of matter, not the chemical composition.