1. Classifying Changes of Matter: Physical vs. Chemical

2. Physical Physical Change  A change in matter from one form to another without changing its chemical properties  (most can be reversed)  No change in atoms/molecules

3. Physical Change Examples =  Change in state or phase change  Dissolving  Compressing  Light emission/absorption  Electrons passing through metals

4. Physical Change More Examples = boiling of a liquidboiling of a liquid melting of a solidmelting of a solid dissolving a solid in a liquid to give a homogeneous mixturedissolving a solid in a liquid to give a homogeneous mixture making a solutionmaking a solution

5. Chemical Chemical Change Bonds are made / broken Change in oxidation states Bonds are made / broken Change in oxidation states Cl -1 2121 Li +1

6. Examples of Chemical Change Chemical change or chemical reaction — transformation of one or more atoms or molecules into one or more different molecules. Chemical change or chemical reaction — transformation of one or more atoms or molecules into one or more different molecules. Burning hydrogen (H 2 ) in oxygen (O 2 ) gives H 2 O.Burning hydrogen (H 2 ) in oxygen (O 2 ) gives H 2 O.

7. Sure Signs of a Chemical Change Heat Heat Light Light Gas Produced (not from boiling!) Gas Produced (not from boiling!) Precipitate – a solid formed by mixing two liquids together Precipitate – a solid formed by mixing two liquids together

8. Physical vs. Chemical Change Examples: ▫melting ▫flame produced ▫paper cut ▫dissolving salt in water ▫tarnishes in air physical chemical physical chemical

9. Examples: ▫rusting iron ▫mixing mud and water ▫burning a log ▫freezing water ▫grinding spices Physical vs. Chemical Change chemical physical chemical physical

10. A difference between physical change and chemical change is that 1. chemical change involves energy while physical change does not. 2. physical change involves energy while chemical change does not. 3. different kinds of molecules are present after a physical change but not after a chemical change. 4. different kinds of molecules are present after a chemical change but not after a physical change

11. In making a pizza, which process involves a chemical change? 1.Mixing spices for the sauce 2.Slicing pepperoni for the topping 3.Spreading cheese on the pizza 4.Baking the dough to form the crust In making a pizza, which process involves a chemical change? 1.Mixing spices for the sauce 2.Slicing pepperoni for the topping 3.Spreading cheese on the pizza 4.Baking the dough to form the crust