Classifying Changes of Matter: Physical vs. Chemical

1. Classifying Changes of Matter:Physical vs. Chemical

2. Physical Change Physical • 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 liquid • melting of a solid • dissolving a solid in a liquid to give a homogeneous mixture • making a solution

5. 2 1 Chemical Change Chemical • Bonds are made / broken • Change in oxidation states Li +1 Cl-1 Cl-1

6. Examples of Chemical Change • Burning hydrogen (H2) in oxygen (O2) gives H2O. • Chemical change or chemical reaction — transformation of one or more atoms or molecules into one or more different molecules.

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

8. Physicalvs. Chemical Change • physical • chemical • physical • physical • chemical • Examples: • melting • flame produced • paper cut • dissolving salt in water • tarnishes in air

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

10. A difference between physical change and chemical change is that • chemical change involves energy while physical change does not. • physical change involves energy while chemical change does not. • different kinds of molecules are present after a physical change but not after a chemical change. • 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? Mixing spices for the sauce Slicing pepperoni for the topping Spreading cheese on the pizza Baking the dough to form the crust