Physical vs. Chemical Change

Review – Physical Changes 1. A physical property – Can be observed or measured without changing the composition of the substance. 2. What happens during a physical change? Some properties change but the composition does not. 3. Examples of physical changes: Phase changes (melting, freezing, etc.), cutting, crushing,

Review – Physical Changes 4. Physical changes can be classified as reversible or irreversible 5. Ex. of reversible physical change: Melting 6. Ex. of irreversible physical change: Cutting

Review – Chemical Changes 7. Define chemical property: Ability of a substance to undergo a chemical change; Only observed during a chemical change. Ex. Flammability or reactivity 8. Words associated with chemical change: burning rotting, rusting, decomposing, fermenting, exploding, corroding

Review – Chemical Changes 9. What always happens during a chemical change? Composition of matter always changes; reactants change and new products are always formed. 10. Examples of chemical changes: Burning charcoal, burning magnesium, bike metal rusting

Review – Chemical Changes 10. How do you know that a chemical change took place? Matter changes to something new. 11. A chemical change is also called a chemical: reaction. 12. Reactants are: Substances present at the start of the reaction. 13. Products are: Substances formed in a reaction.

4 Possible Clues of Chemical Change 15. Real-life Examples Transfer of energy = Change in color = Gas production = Precipitate forms =

The law of Conservation of Mass 16. The Law of Conservation of Mass states that: matter can not be created or destroyed in a chemical reaction (rxn.) In other words: Mass of reactants = Mass of products