Physical Change:
* Definition: A change in the form or appearance of a substance, but not its chemical composition.
* Examples:
* Breaking a piece of chalk: The chalk changes shape, but it's still calcium carbonate (CaCO3).
* Crushing a rock: The rock becomes smaller pieces, but its chemical makeup remains the same.
* Melting ice: Water changes from solid to liquid, but it's still H2O.
Chemical Change:
* Definition: A change that results in the formation of new substances with different chemical compositions.
* Examples:
* Burning wood: Wood reacts with oxygen, producing ash, carbon dioxide, and other products.
* Digesting food: Complex molecules in food are broken down into simpler substances.
* Rusting metal: Iron reacts with oxygen and water to form iron oxide (rust).
To determine if breaking down something is a physical or chemical change, consider:
* Does the substance's chemical makeup change? If yes, it's a chemical change. If not, it's a physical change.
* Is energy released or absorbed? Chemical changes often involve energy changes (heat, light).
* Is it reversible? Physical changes are often reversible. Chemical changes are usually not reversible without further chemical reactions.
For example, if you are breaking down a piece of paper, it's a physical change if you tear it into smaller pieces. However, it's a chemical change if you burn it.
