1. Chemical Change Reactants Products What happens to bonds in a chemical reaction? Broken, form new bonds

2. Some examples: Word equations Iron + Oxygen iron (III) oxide (word equation for the rusting of iron) Hydrogen peroxide water + oxygen (what happens when you pour this on an open cut? Bubbles of oxygen gas rapidly appear)

3. Methane + oxygen carbon dioxide + water (major component of natural gas)

4. Chemical Equations Fe(s) + O 2 (g) Fe 2 O 3 (s) (rusting of iron) Symbols are used to represent states

5. Chemical Equations H 2 O 2 (aq) MnO2 H 2 O(l) + O 2 (g) Catalyst: a substance that speeds up the rate of a reaction but that is not used up in the reaction. It is neither a reactant nor a product. It is written above the arrow in an equation because it is not part of the reaction.

6. Symbols used in chemical equations (see Table)

7. Review: Write a skeleton outline for the following chemical reaction (include appropriate symbols): -solid sodium hydrogen carbonate reacts with hydrochloric acid to produce the aqueous sodium chloride, water, and carbon dioxide gas. NaHCO 3 (s) + HCl(aq) NaCl(aq) + H 2 O(l) +CO 2 (g)

8. Review: sulfur burns in oxygen to form sulfur dioxide S(s) + O 2 (g) SO 2 (g)

9. Balancing Chemical Equations Use an example of building a bicycle 4 components: frames, wheels, handlebars, and pedals Frame + wheel + handlebar + pedal bicycle (reactants) (product) (why is this word equation inadequate?) F + W + H + P FW 2 HP 2 (this is called an unbalanced equation, in order to balance, the amount of reactants must equal the amount of products)

10. Balancing Chemical Equations coefficient: a small whole number that appears in front of a formula in a balanced chemical equation F + 2W + H + 2P FW 2 HP 2 Balancing a chemical equation is necessary so that it obeys the law of conservation of mass. balanced equation: each side of the equation has the same number of atoms of each element

11. Let’s try a few: H 2 (g) + O 2 (g) H 2 O(l) how would you balance this equation?

12. “Rules for Balancing Equations” count the number of each atom: hydrogen is balanced but oxygen is not put a coefficient of 2 in front of H 2 O, the oxygen is balanced but there are twice as many hydrogen atoms in the product as there are in the reactants to correct this, put a coefficient of 2 in front of H 2 2H 2 (g) + O 2 (g) 2H 2 O(l)

13. Review: Balance the following equations: AgNO 3 + H 2 S Ag 2 S + HNO 3 2AgNO 3 + H 2 S Ag 2 S + 2HNO 3 MnO 2 + HCl MnCl 2 + H 2 O +Cl 2 MnO 2 + 4HCl MnCl 2 + 2H 2 O + Cl 2

14. Demo: Copper(II) chloride with aluminum Activity: “Balancing Chemical Equations”