3. Vocabulary Review  Physical Change – A change in size, shape, or state of an object, yet does not change the actual object.  Chemical Change – A change from one substance into another with different properties. Evidence includes: changes in color, odor, size, or energy either received or given off.

4. Vocabulary  Chemical Reaction – A process of chemical change occurring when compounds change bonds and creating new, different substances.  Chemical Equation – the explanation of a chemical reaction using symbols and numbers to show the atoms involved.  Reactants – Substances that exist before a reaction.  Products – Substances that are formed from a reaction.

5. Understanding Chemical Equations The point of a formula is to sum up and quickly explain a reaction that would otherwise be too long winded. The reactants of one molecule of methane and two oxygen molecules produces the products of one carbon dioxide molecule and two molecules of dihydrogen monoxide. produces CH 4 + O 2 + O 2  CO 2 + H 2 O + H 2 O Reactants Products

6. Understanding Chemical Equations CH 4 + O 2 + O 2  CO 2 + H 2 O + H 2 O Reactants Products is the same equation as 1 CH 4 + 2 O 2  1 CO 2 + 2 H 2 O is the same equation as CH 4 + 2O 2  CO 2 + 2H 2 O

7. CH 4 + 2O 2  CO 2 + 2H 2 0 Reactant SideAtomProduct Side Carbon Hydrogen Oxygen Counting Atoms in Reactions 11 44 4 4 2 + 2 =

8. 6) Are atoms created or destroyed in a chemical reaction? How do you know? What does the picture on the right represent? The products “balance” the reactants. There are exactly the same number of reactant atoms as there are product atoms. Furthermore, the mass on the left equals the mass on the right. Atoms are not created or destroyed. There is exactly the same number of each type of atom in the products as there are in the reactants.

9. 7) In a physical change, like changing state from a solid to a liquid, the substance itself doesn’t really change. Explain how is a chemical change different from a physical change? In a chemical change a new substance with different properties is formed, but in a physical change it only changes size, shape, or state.

10. C 3 H 8 + 5O 2  3 CO 2 + 4 H 2 O Reactant SideAtomProduct Side Carbon Hydrogen Oxygen More Counting Atoms 33 8 8 10 6 + 4 =

11. 1 C 4 H 10 + 13O 2  8 CO 2 + 10 H 2 O Reactant SideAtomProduct Side Carbon Hydrogen Oxygen 48 10 20 26 16 + 10 = When Balancing… YOU CAN NEVER CHANGE THE NUMBER IN THE SUBSCRIPTS. ONLY COEFFICIENTS

12. Conservation of Mass  When a chemical reaction happens, no atoms are created or destroyed.  The number of atoms in the reactants ALWAYS EQUALS the number of atoms in the products.  For a chemical equation to be correct, the equation must be balanced.

13. N 2 + H 2  NH 3 N H KClO 3  KCl + O 2 K Cl O Worked Examples

14. NaCl + F 2  NaF + Cl 2 Na Cl F H 2 + O 2  H 2 O H O Worked Examples

15. What is a chemical change? A chemical change is when a new substance with different properties is formed from the reaction of the REACTANTS.

16. H H H H O O Visualizing Equations 2 H 2 + 1O 2 2 H 2 O

17. H H H H O O Visualizing Equations 4 H 2 + 2 O 2 4 H 2 O H H H H O O

18. H H H H O O Visualizing Equations 6 H 2 + 3 O 2 6 H 2 O H H H H O O H H H H O O

19. H H H H O O Limiting Reactants 6 H 2 + 2 O 2 4 H 2 O + 2H 2 H H H H H H H H O O

20. H H H H O O Limiting Reactants 6 H 2 + 1 O 2 2 H 2 O + 4H 2 H H H H H H H H

21. O O CC H H HH O O C H O Na 1 C 2 H 2 O 2 + 1NaHCO 3 1 NaC 2 H 3 O 2 + 1CO 2 + 1H 2 O

22. O O CC H H HH O O C H O Na O O CC H H HH

23. Types of Reactions 1. Synthesis: (Building something) A+B  AB Example 2H 2 + O 2  2H 2 O End with 1 Product 2. Decomposition: (Destroying something) AB  A +B Example 2NH 3  N 2 + 3H 2 Begin with 1 Reactant

24. Types of Reactions 1. Single Replacement: AX + B  A + BX Example 2K + MgBr 2  2KBr + Mg Switch one partner 2. Double Replacement: AX + BY  AY + BX Example 2 AlBr 3 + 3 K 2 SO 4  6 KBr + Al 2 (SO 4 ) 3 Switch both Partners

25. Types of Reactions 1. Acid Base: Make a Salt and Water AOH + HB  AB + H 2 O Example – NaOH + HCl  NaCl + H 2 O 2. Combustion: Make CO 2 and Water C x H y + O 2  CO 2 + H 2 O Example – CH 4 + 2O 2  CO 2 + 2H 2 O

26. Heat Reactions  Exothermic – in these types of chemical reactions, heat is given off in the process. Example: Burning – Substance combines with Oxygen to form heat, Light, CO2 or Water. (Combustion) Temperature of products rises.  Endothermic – in these types of chemical reactions, heat is absorbed in the process. Example: A cold pack that dissolves a solution in water takes in heat from surrounding environment. Temperature of products lowers.

28.  Exothermic – Reaction in which heat energy is released. “Exo” means outside. Energy is released to the “outside.” Example: Burning – Substance combines with Oxygen to form heat, Light, CO 2 or Water. (Combustion) The Energy of products is lower than reactants, but the temperature of products is higher than reactants (with the excess heat generated)

29. Reaction Progress Exothermic Reaction -Releases energy -Energy of products is lower than reactants.

30.  Endothermic – Reaction in which heat energy is absorbed. “Endo” means “in.” Energy goes IN to the reaction. Example: A cold pack that dissolves a solution in water takes in heat from surrounding environment. The Energy of products is higher than reactants, but the temperature of the reactants is lower due to the absorbed energy.

31. EndoEndothermic Reaction -Absorbs energy -Energy of products is higher than reactants. Reaction Progress

32. Exo or endo? Reaction Progress Energy

33. Exo or endo? Reaction Progress Energy

34. Putting it all together! Remember Types of Reactions?  S = Synthesis:A + B  AB  D = Decomposition:AB  A + B  SR = Single Replacement:AX + B  A + BX  DR = Double replacement:AX + BY  AY + BX  C= Combustion C x H y + O 2  CO 2 + H 2 O

35. Exo or Endo? Reaction Progress Energy What “type” of reaction is this? C 3 H 8 + 5O 2 3CO 2 + 4H 2 O combustion

36. Exo or Endo? Reaction Progress Energy What “type” of reaction is this? 2H 2 + O 2 2H 2 O synthesis

37. Exo or Endo? Reaction Progress What “type” of reaction is this? 2AlBr 3 +3K 2 SO 4 6KBr + Al 2 (SO 4 ) 3 Double replacement

38. Exo or Endo? Reaction Progress What “type” of reaction is this? 2NaCl + F 2 2NaF + Cl 2 Single replacement

39. Exo or Endo? Reaction Progress Energy What “type” of reaction is this? 2KClO 3 2KCl + 3O 2 decomposition

40. Rates of Reactions  Temperature – When temperature is increases, molecular speed is increased, making reactions happen faster. If you slow down the speed (decrease temperature) then the reaction slows down as well. Temperature Up = Reaction Rate Up  Concentration – The amount of substance in a given amount of volume. The higher the concentration, the faster the reaction because the molecules are closer together. Concentration Up = Reaction Rate Up  Surface Area – the amount of the substance that is exposed increases the reaction rate because only outer molecules can actually react. Surface Area Up = Reaction Rate Up

41.  Activation Energy – The minimum amount of energy needed to start a reaction.  Inhibitor – Slows down reactions. Chemicals on cereal boxes slowing down the spoiling of foods.  Catalyst – speeds up reactions without being used up in the process.  Enzymes – Proteins that speed up reaction in your body

42.  Activation Energy – The amount of energy needed to start a reaction. The “hill” in the diagrams. You have to climb the hill before the reaction can start.  Catalyst – Speeds up reactions without being used up or changed in the process. Lowers the activation energy of a reaction. It lowers the hill! (Analogy: Like a matchmaker setting up a couple.)

43. Would you rather be a catalyzed or uncatalyzed reaction? Which do you think occurs more easily? Is this exo or endothermic? cc A catalyst lowers the Activation Energy (the hill!)

44. Catalysts you have heard about!  Enzymes = Your body’s catalysts! Ex. Enzymes in your saliva help food be broken down FAST!

45.  Can a person act like a catalyst? A “catalyst” is a person who gets something started or speeds something up (MLK’s speech, starting a club, a starting a winning streak on a sports team, etc).