1. CHEMICAL REACTIONS
Chapter 7

2. Changes PHYSICAL CHEMICAL Only affects the size, shape and state.
Amount of energy involved in each state varies.
CHEMICAL
Atoms are rearranged.
Bonds broken
new substance created
Energy released or absorbed

3. Physical OR Chemical Reactions?

4. Lab: Conservation of Mass Physical or Chemical Change?
A – Dissolving Salt and Water
B – Melting Ice
C – Lead nitrate mixed with sodium chloride OR sodium iodide
D – copper and sulfur
E – water and alka-seltzer

5. Lab: Conservation of Mass Physical or Chemical Change?
A – Dissolving Salt and Water
B – Melting Ice
C – Lead nitrate mixed with sodium chloride OR sodium iodide
D – copper and sulfur
E – water and alka-seltzer
Physical
Chemical

6. Chemical Reactions Rearrange atoms
REACTANTS PRODUCTS
C2H5OH + 3O CO2 + 3H2O
New product atoms and old reactant atoms are not created or destroyed. Mass is always conserved.

7. Energy and Reactions Energy must be added to break bonds Energy Heat
Electricity
Sound
light

8. Energy and Reactions
Forming bonds releases energy

9. Energy and Reactions

10. Examples Exothermic Endothermic Combustion of Methane (Natural Gas).
Adding concentrated sulfuric acid to water
Acid/Base reactions         Dissolving a strong acid or strong base
Endothermic
Photosynthesis
Dissolving most salts into water (exceptions)
Decomposition reactions         A –– > B + C

11. Diatomic Molecules Most elemental gases do not exist as single atomsH2 N2 F2 O2 I2
Cl2
Br2

12. 7.2 Chemical Reactions Are
Represented by Chemical
Equations

13. Chemical Equation
A representation in which reactants are written before an arrow and products are written after the arrow.

14. Reactants
Products

15. Substances that are about to chemically react.
Reactants
Substances that are about to chemically react.

16. Substances that are formed from a chemical reaction.
Products
Substances that are formed from a chemical reaction.

17. Animation
“CO2flask.mov”

18. Reactants

19. Carbon,C
Reactants

20. Carbon,C
Oxygen, O2
Reactants

21. Chemical reaction

22. Products

23. Carbon Dioxide, CO2
Products

24. Coefficients
Integers used to indicate the ratio by which reactants react and products form.

25. H2 + O2
H2O
Reactants
Products

26. 2 H2 + O2
H2O
Reactants
Products

27. 2 H2 + 1 O2
H2O
Reactants
Products

28. 2 H2 + 1 O2 2
H2O
Reactants
Products

29. 2 H2 + O2 2
H2O
Reactants
Products

30. 2 H2
(g) + O2
(g) 2
H2O
(g)
Reactants
Products

31. Balancing Chemical Equations

32. Balancing Guidelines Balance one element at a time.
2) If you incidentally unbalance
an element leave it alone.
3) Make successive passes.

33. Al2O3 + C Al +
CO2

34. Al2O3 + C Al +
CO2
(not balanced)

35. Al2O3 + C Al +
CO2

36. Al2O3 + C Al +
CO2 Al Al C Al O C O O O O

37. Al2O3 + C Al +
CO2

38. 2
Al2O3 + C Al +
CO2

39. 2
Al2O3 + C Al +
CO2 Al Al Al C O C O O O O Al

40. 2
Al2O3 + C Al +
CO2

41. 2 2 3
Al2O3 + C Al +
CO2

42. 2 2 3 Al2O3 + C Al + CO2 O C O Al Al Al O O O C O C O Al O C O Al Al O

43. 2 2 3
Al2O3 + C Al +
CO2

44. 2 3 2 3
Al2O3 + C Al +
CO2

45. 2 3 2 3 Al2O3 + C Al + CO2 C O C O Al Al Al O O O C O C O Al C O C O

46. Balanced 2 3 4 3 Al2O3 + C Al + CO2 C O C O Al Al Al O O O C O C O Al

47. Balanced 2 3 4 3
Al2O3 + C Al +
CO2

48. not balanced
Na2SO3 + S8
Na2S2O3

49. Na2SO3 + S8
Na2S2O3

50. 1
Na2SO3 1 + S8
Na2S2O3

51. 1
Na2SO3 1 + S1
Na2S2O3

52. 1
Na2SO3 1 + S8
Na2S2O3

53. 1 1
Na2SO3 1 + S8
Na2S2O3 8

54. 1 1
Na2SO3 1 + S8
Na2S2O3 8 S S S S S S S S

55. 1 1
Na2SO3 1 + S8
Na2S2O3 8 S S S S S S S S

56. 1 1
Na2SO3 1 + S8
Na2S2O3 8 S S S S S S S S

57. 1 1
Na2SO3 1 + S8
Na2S2O3 8 S S S S S S S S

58. 1 1
Na2SO3 1 + S8
Na2S2O3 8

59. 1 1
Na2SO3 1 + S8
Na2S2O3 8

60. 1 8 1
Na2SO3 S8 1 +
Na2S2O3 8

61. 1 8 x 8 8 8
Na2SO3 + S8
Na2S2O3

62. 1 8 x = 1 8 8 8
Na2SO3 + S8
Na2S2O3

63. 8 1 8
Na2SO3 + S8
Na2S2O3

64. Balanced 8 1 8
Na2SO3 + S8
Na2S2O3

65. 7.1 Chemical Reactions Are
Represented by Chemical
Equations

66. 7.2 Chemists Use Relative
Masses to Count Atoms
and Molecules

67. TYPES OF REACTIONS
Chapter 7

68. Types of Reaction Fe + O2 Fe2O3 1. Addition Reactions (aka synthesis)
A + B AB
2 or more substances combine to form a new compound.
small molecules join to form chains -
polymerization
Fe + O2 Fe2O3

69. Types of Reactions 2 H2O 2 H2 + O2 2. Decomposition Reactions AB A + B
compounds are broken apart into smaller substances
Example: Electrolysis of water
2 H2O H2 + O2

70. Types of Reactions Single – Displacement Reaction AX + B BX + A
One element replaces a similar element in a compound
Aka Single – Replacement Reaction

71. Types of Reactions Double – Displacement Reaction AB + CD AD + CB
Aka double –replacement reactions
Ions from 2 compounds in solution exchange places to produce 2 new compounds.
One of the compounds is usually …
A precipitate
A gas that bubbles off
A molecular compound like water

72. Types of Reactions Combustion Reactions These use O2 as a reactant
One product contains O and the other usually H2O
Carbon cpd. + O CO2 + H2O
___________________________________________________________________________________________________________________

73. Importance of Good Air Supply
Types of Reactions
Combustion Reactions
These use O2 as a reactant
One product contains O , usually H2O
____________________________________________________________________________________________________________________________
Importance of Good Air Supply
2CH4 + 4O2 2CO2 + 4H2O
2CH4 + 3O2 2CO + 4H2O
2CH4 + 2O2 2C H2O

74. Chapter 7.1 Energy in Reactions

75. Examples Exothermic Endothermic Combustion of Methane (Natural Gas).
Adding concentrated sulfuric acid to water
Acid/Base reactions         Dissolving a strong acid or strong base
Endothermic
Melting of ice
evaporation of water
boiling of water.
Photosynthesis
Dissolving most salts into water (exceptions)
Decomposition reactions         AB –– > A + B

76. Other Terms - refers to the ease in which the reactions occurs
Exergonic
Most cases: are exothermic
Bioluminescence
Respiration
Endergonic
Most cases: are endothermic
Photosynthesis

77. Endothermic Reaction (ex. Photosynthesis) – takes in energy- cold pack
Exothermic Reactions (ex. Cell Respiration) – gives off energy– hot pack
Plus more balancing reactions to show conservation of mass and energy

78. __Cu+__O2__CuO __Cu+__S__CuS H2O  2H2 + O2 CuCl2 + Zn  ZnCl2 + Cu
            
860 × fphoto.photoshelter.com
605 × fphoto.com
__Cu+__O2__CuO __Cu+__S__CuS
H2O  2H2 + O2
CuCl2 + Zn  ZnCl2 + Cu
HCl + NaOH  HOH + NaCl
PbNO3 + KI  PbI + KNO3
PbNO3+NaClPbCl +NaNO3
4CH3 + 7O2 4CO2 + 6H2O

79. 2Cu+O22CuO or Cu+SCuS __H2O  __H2 + __O2 CuCl2 + Zn  ZnCl2 + Cu
            
448 × witcombe.sbc.edu
2Cu+O22CuO or Cu+SCuS
__H2O  __H2 + __O2
CuCl2 + Zn  ZnCl2 + Cu
HCl + NaOH  HOH + NaCl
PbNO3 + KI  PbI + KNO3
PbNO3+NaClPbCl +NaNO3
4CH3 + 7O2 4CO2 + 6H2O

80. __CuCl2 + __Zn  __ZnCl2 + __Cu
2Cu+O22CuO or Cu+SCuS
2H2O  2H2 + O2
__CuCl2 + __Zn  __ZnCl2 + __Cu
HCl + NaOH  HOH + NaCl
PbNO3 + KI  PbI + KNO3
PbNO3+NaClPbCl +NaNO3
4CH3 + 7O2 4CO2 + 6H2O

81. 4CH3 + 7O2 4CO2 + 6H2O 2Cu+O22CuO or Cu+SCuS 2H2O  2H2 + O2
CuCl2 + Zn  ZnCl2 + Cu
__HCl + __NaOH  __HOH + __NaCl
__PbNO3 + __KI  __PbI + __KNO3
__PbNO3+__NaCl__PbCl +__NaNO3
4CH3 + 7O2 4CO2 + 6H2O

82. 2Cu+O22CuO or Cu+SCuS 2H2O  2H2 + O2 CuCl2 + Zn  ZnCl2 + Cu
HCl + NaOH  HOH + NaCl
PbNO3 + KI  PbI + KNO3
PbNO3+NaClPbCl +NaNO3
__CH4 + __O2 __CO2 + __H2O

83. Examples Exothermic Endothermic Combustion of Methane (Natural Gas).
Adding concentrated sulfuric acid to water
Acid/Base reactions         Dissolving a strong acid or strong base
Endothermic
Melting of ice
evaporation of water
boiling of water.
Photosynthesis
Dissolving most salts into water (exceptions)
Decomposition reactions         A –– > B + C