1. Chemical Reactions Unit Learning Goal #1: Identify evidence of chemical reactions and differentiate between the different types of reactions.

2. Evidence for a Chemical Reaction Precipitation Precipitation –A solid formed from a solution can result from a chemical change.

3. Evidence for a Chemical Reaction Gas Production Gas Production –Fizzing, bubbling Color Changes Color Changes Odor Changes Odor Changes

4. Evidence for a Chemical Reaction Energy Changes Energy Changes –Exothermic  Heat is released (feels hot) –Endothermic  Heat is absorbed (feels cold) –Light can be absorbed or released also without a temperature change.

6. Predicting Whether a Reaction Will Occur Most common Driving Forces. Most common Driving Forces. –Formation of a solid –Formation of water –Transfer of electrons –Formation of a gas

7. Predicting What Will Be Formed From a Reaction Solids Forms Solids Forms –Precipitation  Reaction where a solid is formed. –Ionic Compounds  Contains only two types of ions.  Anion and cation  Strong Electrolyte: A substance that dissolved in water produces ions.

8. Steps for predicting precipitates Step 1 – Write the reactants as they actually exist before any reaction occurs. Step 1 – Write the reactants as they actually exist before any reaction occurs. Step 2 – Consider the various solids that could form. Step 2 – Consider the various solids that could form. Step 3 – Use the solubility rules to decide whether a solid forms, and, if so, to predict the identity of the solid. Step 3 – Use the solubility rules to decide whether a solid forms, and, if so, to predict the identity of the solid.

9. –Soluble Solid  Solid that readily dissolves in water. –Insoluble solid and slightly soluble solid  Very small amount dissolves in water, the majority stays solid.

12. Types of Reactions Decomposition Reactions Decomposition Reactions –A compound breaks down into two or more simpler substances. –AB  A + B

13. Types of Reactions Synthesis Reactions Synthesis Reactions –Two or more substances combine to form a single product. –A + B  AB Zn + I  ZnI

14. Types of Reactions Single-displacement (replacement) Reactions Single-displacement (replacement) Reactions –One element takes the place of another in a compound. –A + BC  B + AC

15. Acids React with Active Metals Acids react with active metals to form salts and hydrogen gas. Mg + 2HCl  MgCl 2 + H 2 (g) Zn + 2HCl  ZnCl 2 + H 2 (g) Mg + H 2 SO 4  MgSO 4 + H 2 (g)

16. Double-displacement (replacement) Reactions Double-displacement (replacement) Reactions –The positive portions of two ionic compounds are interchanged. –AB + CD  CB + AD Types of Reactions

17. Acid/Base Reaction Acid/Base Reaction –Reaction between an acid and a base that produces water. Types of Reactions HCl + NaOH  NaCl + H 2 O H 2 SO 4 + 2NaOH  Na 2 SO 4 + 2H 2 O 2HNO 3 + Mg(OH) 2  Mg(NO 3 ) 2 + 2H 2 O

18. Types of Reactions Combustion Combustion –The vigorous and exothermic oxidation- reduction reaction that takes place between certain substances and oxygen. –Results in a flame. Methane Oxygen Carbon Dioxide Water

19. Combustion Reactions Combustion Reactions –One in which a substance rapidly combines with oxygen to form one or more oxides. –A + O  AO (oxide) Types of Reactions

20. Oxidation-Reduction Reaction Oxidation-Reduction Reaction –A reaction that involves a transfer of electrons.