* Water boiling: This is a physical change. Water changes state from liquid to gas (steam), but its chemical composition (H₂O) remains the same.
* Nails rusting: This is a chemical reaction. Iron (Fe) in the nail reacts with oxygen (O₂) in the air and water (H₂O) to form iron oxide (Fe₂O₃), commonly known as rust. The chemical composition of the nail changes.
* Sugar dissolving: This is a physical change. Sugar molecules disperse throughout the water, but they don't change their chemical structure (C₁₂H₂₂O₁₁). It's a change in the arrangement of the sugar molecules, not their composition.
* Wax melting: This is a physical change. Wax changes state from solid to liquid, but its chemical composition remains the same.
In summary:
* Chemical Reaction: Nails rusting
* Physical Changes: Water boiling, sugar dissolving, wax melting
