1. Chemical Reactions

2. What is a chemical reaction? A chemical reaction is the process by which substances undergo change to produce different substances, with different properties These new substances have different properties from the original substances

3. Clues to chemical reactions Gas Formation Solid Formation Color change Energy change

5. Breaking and making bonds New substances are formed in chemical reactions because chemical bonds are broken, atoms rearranged, and new bonds form to form new substances

6. Chemical formulas Shorthand notation for a chemical compound Includes subscripts – number written below and to the right of the symbol to let you know the number of elements present

7. Chemical equations Shorthand description of a chemical reaction

8. Reacts yield products Reactants – starting materials in a chemical reaction Products – substances formed from a reaction Coefficient – number placed in front of a chemical symbol or formula

9. Type of Reaction Definition Equation Synthesis Decomposition Single Replacement Double Replacement A = Red B = Blue C = Green D = Yellow A + B → AB AB → A + B AB + C → AC + B AB + CD → AC + BD Two or more elements or compounds combine to make a more complex substance Compounds break down into simpler substances Occurs when one element replaces another one in a compound Occurs when different atoms in two different compounds trade places

10. Law of Conservation of Mass Mass is neither created nor destroyed in ordinary chemical and physical changes A chemical equation must show the same number and kind of atom on both sides of the arrow Balancing Equations

11. Energy released in exothermic reactions Exo means “exit” and thermic means “heat” or “energy” EXAMPLES:  Glow sticks  Flashlight  Campfire  Fireworks

12. Energy is absorbed in endothermic reactions Endo means “go in” and thermic means “heat” or “energy” Examples  Ice pack

13. Energy is conserved – It's a LAW! Law of Conservation of Energy Energy can be neither created nor destroyed