* Chemical reactions involve the formation of new substances with different chemical compositions. When water boils, it changes from liquid to gas (steam), but the chemical formula remains the same (H₂O). The molecules themselves don't change, just their arrangement and energy levels.
* Boiling is a physical change. It's a change in the state of matter due to changes in temperature and pressure. The water molecules are still the same, just spread out further apart in the gas phase.
Here's a simple analogy: Think about melting ice. Ice is just frozen water (H₂O). When it melts, it becomes liquid water, still H₂O. It's a physical change, not a chemical reaction. Boiling water is similar.
