1. Unit 5 Chemical Reactions Chapter 8 Sec. 1

2. Objectives Indications of Chemical Reactions -How do you know a chemical reaction has happened? Chemical Equations -How do you give/get information from a chemical equation Balancing Equations -Matter is not created or destroyed

3. Chemical Reactions To prove that one or more substances have undergone a change in identity...Need Chemical Analysis BUT in the meantime Observed Changes can strongly indicate a chemical reaction

4. Indications of a Chemical Reaction 1)Production of Heat 2)Production of Light 3)Production of a gas 4)Production of a precipitate

5. A solid that is produced in a chemical reaction and separates from solution Vocab: Precipitate

6. Chemical Equations Represent the identities and relative amounts of reactants and products in a chemical reaction with symbols and formulas Reactants Products “yield”

7. Chemical Equation Example Zn (s) + HCl (aq) --> ZnCl 2(aq) + H 2(g) Reactants “yield” Products Zinc -solid Hydrochloric Acid -aqueous solution Zinc Chloride - solution Hydrogen - gas

8. Important Symbols pg. 246 “yields” -indicates results reversible reaction-can go both ways (s) (l) (aq) (g) substance in the solid state substance in the liquid state substance in the aqueous state (water solution) substance in the gaseous state heat 2 atm 0 oC MnO 2 Reaction needs heat to get started Reaction occurs at the pressure indicated Reaction occurs at the temperature indicated Reaction needs a catalyst to get started

9. Clean-Up This Mess! Zn (s) + HCl (aq) --> ZnCl 2(aq) + H 2(g) ZnCl 2(aq) + Na(OH) (aq) --> Zn(OH) (s) + NaCl (s) + H 2 O Zinc Chloride + Sodium Hydroxide --> Zinc Hydroxide + Sodium Chloride + Water

10. Practice Word & Formula Equations Methane + Oxygen --> Carbon Dioxide + Water CH 4(g) + O 2(g) --> CO 2(g) + H 2 O (l) Predict the Products “OMG! Where’d that 2 come from?!”

11. Memorize KNOW this... The following elements exist as diatomic molecules: Hydrogen= H 2 (g) Nitrogen= N 2 (g) Oxygen= O 2 (g) Fluorine= F 2 (g) Chlorine= Cl 2 (g) Bromine= Br 2 (l) Iodine= I 2 (s) When using ANY of the listed elements in a chemical equation USE AS DIATOMIC MOLECULES

12. Naming Compounds Review Determine Compound Type Ionic Covalent Metallic Use metal name Ex: Zn = Zinc Cu 2 = Copper Transition Metal & Non Metal Cation & Anion -Use prefixes Ex: CO = carbon monoxide N 2 O 2 = dinitrogen dioxide -Use Reverse criss-cross method to determine charge on metal -Use roman numerals to indicate that charge Ex: Fe 2 O 3 = Iron (III) Oxide -Use criss-cross method to determine ratio of ion subscripts Add -ide to anion Ex: MgCl 2 = Magnesium Chloride

13. More Practice Word & Formula Equations On your own, write the word and formula equation for each of the following chemical reactions. 1) Hydrogen peroxide in an aqueous solution decomposes to produce oxygen and water. 2) Solid copper metal reacts with aqueous silver nitrate to produce solid silver metal and aqueous copper nitrate. 3) Solid zinc metal reacts with aqueous copper sulfate to produce solid copper metal and aqueous zinc sulfate.

14. More Practice Word & Formula Equations On your own, translate the following chemical equation into a sentence: 1) 2ZnO (s) + C (s) --> 2Zn (s) + CO 2(g) 2) Na 2 O (s) + 2CO 2(g) + H 2 0 (g) --> 2NaHCO 3

15. Chemical Equations Cont. 1) MUST show ALL reactants and products 2) MUST contain correct formulas 3) MUST follow The Law of Conservation of Mass