1. Chemical vs. Physical Changes

2.  the substances are not altered chemically, but are merely changed to another phase (i.e. gas, liquid, solid) or separated or combined. No change occurs in the identity of the substance Physical Change

3. Chemical change   the substances are altered chemically and display different physical and chemical properties after the change.   Atoms in the reactants are rearranged to form one or more different substances   Old bonds are broken; new bonds form

4. Indicators/Signs of a Chemical Change (these are not fool proof) Chemists Get Practice Trying Labs Chemists Get Practice Trying Labs –Color change –Gas/bubbles –Precipitate, ppt (a solid forms) –Temperature change Exothermic (hot) or endothermic (cold) Exothermic (hot) or endothermic (cold) –Light given off   Typically, more than one indicator will be seen.

5. Learning Check Classify each of the following as a Classify each of the following as a 1) physical change or 2) chemical change 1) physical change or 2) chemical change A. ____ a burning candle B. ____ melting ice C. ____ toasting a marshmallow C. ____ toasting a marshmallow D. ____ cutting a pizza D. ____ cutting a pizza E. ____ Tarnished silver E. ____ Tarnished silver

6. Solution Classify each of the following as a Classify each of the following as a 1) physical change or 2) chemical change 1) physical change or 2) chemical change A. __2__ a burning candle B. __1_ melting ice C. __2__ toasting a marshmallow C. __2__ toasting a marshmallow D. __1__ cutting a pizza D. __1__ cutting a pizza E. __2__ tarnished silver E. __2__ tarnished silver

7. Chemical Reaction A process in which at least one new substance is produced as a result of chemical change.

8. In a chemical reaction The way atoms are joined is changed The way atoms are joined is changed Atoms aren’t created or destroyed. Atoms aren’t created or destroyed. Can be described several ways: Can be described several ways: –In a sentence Copper reacts with chlorine to form copper (II) chloride. Copper reacts with chlorine to form copper (II) chloride. –In a word equation Copper + chlorine  copper (II) chloride Copper + chlorine  copper (II) chloride –Formulas Cu+ Cl 2  CuCl 2 Cu+ Cl 2  CuCl 2

9. A Chemical Equation Reactants Products Reactants Products

10. Conservation of Mass and Energy Mass and Energy cannot be created or destroyed, but can change form Mass and Energy cannot be created or destroyed, but can change form

11. Symbols used in equations  separates the reactants from products  separates the reactants from products –Read as “reacts to form” or “yields” + read as “and” or “reacts with” + read as “and” or “reacts with” (s) after the formula -solid (s) after the formula -solid (g) after the formula -gas (g) after the formula -gas (l) after the formula –liquid (l) after the formula –liquid (aq) after the formula- aqueous solution (aq) after the formula- aqueous solution –Dissolved in water.

12. More Symbols used in Equations  used after a product indicates a gas; same as (g)  used after a product indicates a gas; same as (g)  used after a product indicates a solid or ppt (precipitate); same as (s)  used after a product indicates a solid or ppt (precipitate); same as (s)

13. Even More Symbols used in Equations indicates a reversible reaction (More later) indicates a reversible reaction (More later) shows that heat is supplied to the reaction shows that heat is supplied to the reaction is used to indicate a catalyst used supplied, in this case, platinum. is used to indicate a catalyst used supplied, in this case, platinum.

14. What is a catalyst? A substance that speeds up a reaction without being changed by the reaction. A substance that speeds up a reaction without being changed by the reaction. Enzymes are biological or protein catalysts. Enzymes are biological or protein catalysts.

15. Diatomic elements There are 8 elements that never want to be alone. There are 8 elements that never want to be alone. If they are not with another element, they form diatomic molecules. If they are not with another element, they form diatomic molecules. H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2, and At 2 H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2, and At 2 Brother HON CLIF Brother HON CLIF 1 + 7 pattern on the periodic table 1 + 7 pattern on the periodic table

17. Sulfur & Phosphorus Sulfur, when alone, exists as S 8 Phosphorus, when alone, exists as P 4