* Physical Changes: These are changes in the form or appearance of matter, but not its chemical composition. The molecules themselves stay the same.
* Examples:
* Freezing water: Liquid water (H₂O) becomes solid ice (H₂O), but the molecules are still water.
* Boiling water: Liquid water turns into water vapor (gas), but the molecules are still H₂O.
* Cutting paper: The paper is divided into smaller pieces, but it's still paper (cellulose).
* Melting ice cream: The ice cream softens, but it's still the same mixture of ingredients.
* Chemical Changes: These changes involve a change in the chemical composition of matter, forming new substances.
* Examples:
* Burning wood: Wood reacts with oxygen to produce ash, carbon dioxide, and water.
* Baking a cake: Ingredients react chemically to form a cake.
* Rusting iron: Iron reacts with oxygen and water to form iron oxide (rust).
Key Takeaway: Physical changes are reversible (you can often reverse them), while chemical changes are usually not reversible.
