* Chemical Reaction: Involves the formation of new substances with different chemical compositions.
* Physical Change: Alters the form or appearance of a substance but not its chemical makeup.
Here's what happens when water boils:
1. Heat Energy: Adding heat provides energy to the water molecules.
2. Increased Vibration: The molecules vibrate faster and move further apart.
3. Change of State: The water molecules gain enough energy to overcome the forces holding them together as a liquid.
4. Steam: They escape as gas (water vapor or steam), which is still chemically H₂O but in a different state.
Key Point: The chemical formula of water (H₂O) remains the same, both as a liquid and as a gas (steam). This means no new substances are formed, making it a physical change.
