1. Chapter 2
Section 2


2. Rates of
Chemical
Reaction
s

3. How Fast?

4. Some reactions need some help
to get started, others do not.

5. “What is that
extra help called?”

6. Activation Energy

7. The minimum
amount of energy needed
to start a reaction.

8. Let’s look at an example:
2O2 + CH4 --> CO2 + 2H2O

10. Activation Energy
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11. Activation Energy
 For a reaction to begin, the molecules must bump into
each other or collide with enough force.
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12. Activation Energy
 For a reaction to begin, the molecules must bump into
each other or collide with enough force.
 The reactants must smash into each other with a certain
amount of energy. If they do not, the reaction will not
occur.
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13. Activation Energy
 For a reaction to begin, the molecules must bump into
each other or collide with enough force.
 The reactants must smash into each other with a certain
amount of energy. If they do not, the reaction will not
occur.
 This energy is called, activation energy.
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14. Activation Energy
 For a reaction to begin, the molecules must bump into
each other or collide with enough force.
 The reactants must smash into each other with a certain
amount of energy. If they do not, the reaction will not
occur.
 This energy is called, activation energy.
 This is also true for reactions that release energy when
they react. An example is gasoline burning.
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15. When gasoline is spilled it does not burst into flames.

16. A highly flammable material, which cannot be extinguished
by wind or rain needs to be lit in order to burn.

17. Rate of Reaction?

18. How fast a reaction occurs
after it has started.

19. You can measure
Reaction Rate by:
- how quickly one of the
reactants is consumed,
or
- how quickly one of the
products is created

20. Rate of Reaction - Fast is Good

21. Rate of Reaction - Fast is Bad

22. What can we do to control
reaction rate?

23. Temperature
Changes Rate

24. Temperature
Changes Rate

25. Temperature
Changes Rate
 Slow the ripening of fruit by putting them in the
refrigerator.

26. Temperature
Changes Rate
 Slow the ripening of fruit by putting them in the
refrigerator.
 Meat and fish decompose faster at higher
temperatures, producing toxins that can make you
sick. Keep them chilled helps slow the
decomposition rate.

27. Temperature
Changes Rate
 Slow the ripening of fruit by putting them in the
refrigerator.
 Meat and fish decompose faster at higher
temperatures, producing toxins that can make you
sick. Keep them chilled helps slow the
decomposition rate.
 Bacteria grow faster at higher temperature.

28. Temperature Affects Rate

29. Temperature Affects Rate

30. Temperature Affects Rate
 Most chemical reaction speed up when
temperature increase.

31. Temperature Affects Rate
 Most chemical reaction speed up when
temperature increase.
 The atoms and molecules are always
moving, and they move faster at higher
temperatures.

32. Temperature Affects Rate
 Most chemical reaction speed up when
temperature increase.
 The atoms and molecules are always
moving, and they move faster at higher
temperatures.
 Faster molecules collide with each other
more often and with greater force, which
may be enough to break the old bond.
This is activation energy.

33. Concentration
Affects Rate

34. Concentration?

35. Amount of substance
in a certain volume.

36. Surface Area Affects Rate
10 cm
10 cm
10 cm

37. Surface Area Affects Rate
Surface Area = 600 cm2
10 cm
10 cm
10 cm

38. Surface Area Affects Rate
Surface Area = 600 cm2
10 cm That is the
amount of surface
10 cm that would be
10 cm touching the other
reactant.

39. Surface Area Affects Rate
What if we cut out little cubes? 1cm x 1cm
10 cm
10 cm
10 cm

40. Surface Area Affects Rate
What if we cut out little cubes? 1cm x 1cm
10 cm How many cubes
10 cm would we have?
10 cm

41. Surface Area Affects Rate
What if we cut out little cubes? 1cm x 1cm
10 cm How many cubes
10 cm would we have?
10 cm 1000 cubes

42. Surface Area Affects Rate
What if we cut out little cubes? 1cm x 1cm
10 cm How many cubes
10 cm would we have?
10 cm 1000 cubes
What would be
the SA of one of
the cubes?

43. Surface Area Affects Rate
What if we cut out little cubes? 1cm x 1cm
10 cm How many cubes
10 cm would we have?
6cm 2 10 cm 1000 cubes
What would be
the SA of one of
the cubes?

44. Surface Area Affects Rate
What is the total SA of all the cubes?
10 cm
10 cm
10 cm

45. Surface Area Affects Rate
What is the total SA of all the cubes?
10 cm 6cm 2 x 1000 =
10 cm
10 cm

46. Surface Area Affects Rate
What is the total SA of all the cubes?
10 cm 6cm 2 x 1000 =
10 cm
6000 cm2
10 cm

47. Surface Area Affects Rate
What is the total SA of all the cubes?
10 cm 6cm 2 x 1000 =
10 cm
6000 cm2
10 cm
SA of Whole cube = 600 cm2
SA of cut up cube = 6000 cm2

48. Surface Area Affects Rate
That’s a BIG difference!
10 cm
10 cm
10 cm

49. Surface Area Affects Rate
That’s a BIG difference!
10 cm
10 cm
10 cm
SA of Whole cube = 600 cm2
SA of cut up cube = 6000 cm2

50. Slowing
Down
Reactions

51. Inhibitor?

52. A substance that slows down
a chemical reaction. An
inhibitor makes the formation
of a certain amount of
product take longer.

53. Inhibitor
Butylated hydroxytoluene (BHT)

54. Speed Up Reactions

55. Catalyst?

56. A substance that speeds up
a chemical reaction.
Catalyst’s do not appear in a
chemical equation because they
are not changed permanently
or used up.

57. Catalysts
- provide a surface for the
reaction to take place,
or
- reduce the activation energy
needed to start the reaction

58. 38

59. Catalytic Converter

60. Catalytic Converter

61. Catalytic Converter
In vehicles, the exhaust passes through the
catalyst.

62. Catalytic Converter
In vehicles, the exhaust passes through the
catalyst.
Catalysts will speed up the reactions that
change incompletely burned substances that
are harmful, such as carbon monoxide, into
less harmful substances like CO2 and H2O.

63. Catalytic Converter
In vehicles, the exhaust passes through the
catalyst.
Catalysts will speed up the reactions that
change incompletely burned substances that
are harmful, such as carbon monoxide, into
less harmful substances like CO2 and H2O.
This results in cleaner air.

64. Catalytic Converter

65. Catalytic Converter

66. Enzymes are Specialists!

67. Enzyme?

68. Large protein molecules that
speed up reactions needed for
your cells to work properly.
- convert food to fuel
- build bone and muscle tissue
- convert extra energy to fat
- produce other enzymes

70. Other Uses of Enzymes
One example is Proteases - a class of enzymes
that work within cells to break down proteins.
Meat tenderizer is one example of a protease.
Contact lens cleaning solutions also contain
proteases that break down proteins formed by
your eyes that can collect on your lenses and
cloud your view.

71. Finished the
KNP!
So, lets see a
catalyst at work!