1. CHEMISTRY 103 Fall 2016 1

2. Why Study Chemistry? Think about current issues in the news. 2

3. Why Study Chemistry? Think about current issues in the news. Energy sources 3

4. Why Study Chemistry? Think about current issues in the news. Energy sources Greenhouse effect 4

5. Why Study Chemistry? Think about current issues in the news. Energy sources Greenhouse effect Pollution 5

6. Why Study Chemistry? Think about current issues in the news. Energy sources Greenhouse effect Pollution Ozone problem 6

7. Why Study Chemistry? Think about current issues in the news. Energy sources Greenhouse effect Pollution Ozone problem Food additives 7

8. Why Study Chemistry? Think about current issues in the news. Energy sources Greenhouse effect Pollution Ozone problem Food additives Drugs 8

9. INTRODUCTION CHEMISTRY: A science that deals with the composition, structure, and properties of substances and of the changes they undergo. There are six major subdivisions of Chemistry: 9

10. 1.Organic chemistry: Covers the compounds of carbon and hydrogen (hydrocarbons). All compounds derived from hydrocarbons. 10

11. 1.Organic chemistry: Covers the compounds of carbon and hydrogen (hydrocarbons). All compounds derived from hydrocarbons. 2.Inorganic chemistry: Covers all the elements, and all compounds, except the hydrocarbons and their derivatives. 11

12. 1.Organic chemistry: Covers the compounds of carbon and hydrogen (hydrocarbons). All compounds derived from hydrocarbons. 2.Inorganic chemistry: Covers all the elements, and all compounds, except the hydrocarbons and their derivatives. 3. Physical chemistry: Measurement of physical properties. Interpretation of physical and chemical properties. 12

13. 4.Biochemistry: Study of pure substances and chemical reactions in living systems. 13

14. 4.Biochemistry: Study of pure substances and chemical reactions in living systems. 5.Analytical chemistry: Measurement of the amounts of substances. Measurement of chemical composition of materials. Separation of the components of mixtures. 14

15. 4.Biochemistry: Study of pure substances and chemical reactions in living systems. 5.Analytical chemistry: Measurement of the amounts of substances. Measurement of chemical composition of materials. Separation of the components of mixtures. 6. Theoretical chemistry: Mathematical description of chemical structures and of chemical changes. 15

16. Scientific Method 16

17. Scientific Method A series of steps used to solve scientific problems. 17

18. Scientific Method A series of steps used to solve scientific problems. Objective: Some problem to be solved, e.g. how oxygen gas binds to the hemoglobin molecule in our blood. 18

19. Collection of data: Once the goal is defined, the next step involves making careful observations and collecting bits of information about the system. The bits of information are called data. The word system here means that part of the universe that is under investigation. 19

20. The information obtained may be both qualitative or quantitative. 20

21. The information obtained may be both qualitative or quantitative. Qualitative: general and non-mathematical. E.g. the object has a blue color. 21

22. The information obtained may be both qualitative or quantitative. Qualitative: general and non-mathematical. E.g. the object has a blue color. Quantitative : numerical – related to measurements. E.g. the density is 2.1 g/ml. 22

23. Law: After a large amount of data has been collected, it is often desirable to summarize the information in a concise way. This summarizing statement is called a law. 23

24. Law: After a large amount of data has been collected, it is often desirable to summarize the information in a concise way. This summarizing statement is called a law. A law is a concise verbal or mathematical statement of a relation between phenomena that is always the same under the same conditions. 24

25. Hypothesis: Once enough information has been gathered, a tentative explanation for the observations can be formulated – this is the hypothesis. 25

26. Hypothesis: Once enough information has been gathered, a tentative explanation for the observations can be formulated – this is the hypothesis. Further experiments are devised to test the validity of the hypothesis in as many ways as possible. 26

27. The hypothesis provides tentative explanations that must be tested by many experiments. If the hypothesis survives such tests, the hypothesis develops into a theory. 27

28. The hypothesis provides tentative explanations that must be tested by many experiments. If the hypothesis survives such tests, the hypothesis develops into a theory. Theory: A theory is a unifying principle that explains a body of facts and those laws that are based on them. Theories are constantly being tested. If a theory is proved incorrect by experiment, then it must be discarded or modified, so that it becomes consistent with experimental observations. 28

29. Scientific progress is made by modifying old laws and theories or replacing them with new ones. 29

30. Summary – the sequence 30

31. Summary – the sequence 1. Objective 31

32. Summary – the sequence 1. Objective 2.Data collection 32

33. Summary – the sequence 1. Objective 2.Data collection 3.Summarize data, generalization, formulation of law 33

34. Summary – the sequence 1. Objective 2.Data collection 3.Summarize data, generalization, formulation of law 4. Hypothesis (tentative explanation) 34

35. Summary – the sequence 1. Objective 2.Data collection 3.Summarize data, generalization, formulation of law 4. Hypothesis (tentative explanation) 5.Test hypothesis 35

36. Summary – the sequence 1. Objective 2.Data collection 3.Summarize data, generalization, formulation of law 4. Hypothesis (tentative explanation) 5.Test hypothesis 6.Formulate theory 36

37. Summary – the sequence 1. Objective 2.Data collection 3.Summarize data, generalization, formulation of law 4. Hypothesis (tentative explanation) 5.Test hypothesis 6.Formulate theory 7. Further testing 37

38. Summary – the sequence 1. Objective 2.Data collection 3.Summarize data, generalization, formulation of law 4. Hypothesis (tentative explanation) 5.Test hypothesis 6.Formulate theory 7. Further testing 8. Rejection or modification of theory as required to account for new observations. 38

39. Some basic definitions Matter: Anything that occupies space and possesses mass is called matter. 39

40. Some basic definitions Matter: Anything that occupies space and possesses mass is called matter. Mass: The mass of a body is a measure of the quantity of matter contained in that body. 40

41. Some basic definitions Matter: Anything that occupies space and possesses mass is called matter. Mass: The mass of a body is a measure of the quantity of matter contained in that body. Weight: Refers to the force which gravity exerts upon an object. Unfortunately, chemists very frequently use the word “weight” when they mean mass. 41

42. Substance: A substance is a form of matter that has a definite composition and distinct properties. Examples: gold, water, oxygen. 42

43. Substance: A substance is a form of matter that has a definite composition and distinct properties. Examples: gold, water, oxygen. Mixture: A combination of two or more substances in which the substances retain their identities. Examples: air, a solution of table sugar (sucrose) in water. 43

44. Substance: A substance is a form of matter that has a definite composition and distinct properties. Examples: gold, water, oxygen. Mixture: A combination of two or more substances in which the substances retain their identities. Examples: air, a solution of table sugar (sucrose) in water. Note: Mixtures do not have constant composition; samples of air collected in Los Angles will have different composition from samples collected in Eau Claire. 44

45. There are two types of mixtures: homogeneous and heterogeneous. 45

46. There are two types of mixtures: homogeneous and heterogeneous. Homogeneous mixture: The composition is the same throughout. Example: a small amount of sugar completely dissolved in water. 46

47. There are two types of mixtures: homogeneous and heterogeneous. Homogeneous mixture: The composition is the same throughout. Example: a small amount of sugar completely dissolved in water. Heterogeneous mixture: A mixture in which the individual components remain physically separate and can be seen as separate components. Example: a mixture of sugar and sand. 47

48. Any mixture, be it homogeneous or heterogeneous, can be put together and then separated into pure components without any change in the identity of the components, by physical means. 48

49. For example: sugar can be removed from a homogeneous sugar solution by evaporating off the solvent water. 49

50. For example: sugar can be removed from a homogeneous sugar solution by evaporating off the solvent water. A sugar/sand mixture could be separated by dissolving the sugar in water, drying the sand, and reclaiming the sugar by evaporation of the solution. 50

51. For example: sugar can be removed from a homogeneous sugar solution by evaporating off the solvent water. A sugar/sand mixture could be separated by dissolving the sugar in water, drying the sand, and reclaiming the sugar by evaporation of the solution. In the physical separation process, there has been no change in the composition of each substance making up the mixture. 51

52. Physical property: Any property of a substance that can be observed without permanently* changing the substance to form some other substance. Examples: color, density, melting point. * Some exceptions to this. E.g. some compounds decompose at their melting point. A physical property can be specified without reference to any other substance. 52

53. Chemical property: Any property of a substance that cannot be studied without resulting in a permanent change of the substance to form some other substance. 53

54. Chemical property: Any property of a substance that cannot be studied without resulting in a permanent change of the substance to form some other substance. Example: sodium metal is very reactive with water. 54

55. Chemical property: Any property of a substance that cannot be studied without resulting in a permanent change of the substance to form some other substance. Example: sodium metal is very reactive with water. Reactivity is a chemical property that refers to the tendency of a substance to undergo a particular chemical reaction. 55

56. Element: An element is a pure substance that cannot be separated into simpler substances by chemical means. 56

57. Element: An element is a pure substance that cannot be separated into simpler substances by chemical means. Compound: A pure substance composed of two or more elements chemically united in fixed proportions. 57

58. Element: An element is a pure substance that cannot be separated into simpler substances by chemical means. Compound: A pure substance composed of two or more elements chemically united in fixed proportions. Atom: The smallest particle of an element that retains the chemical nature of the element. 58

59. Element: An element is a pure substance that cannot be separated into simpler substances by chemical means. Compound: A pure substance composed of two or more elements chemically united in fixed proportions. Atom: The smallest particle of an element that retains the chemical nature of the element. Molecule: A structure consisting of two or more atoms that are chemically bound together and behave as an independent unit. 59

60. Energy: Is the capacity to do work or produce change. 60

61. Energy: Is the capacity to do work or produce change. Potential Energy: Energy available because of the position of an object. 61

62. Energy: Is the capacity to do work or produce change. Potential Energy: Energy available because of the position of an object. Kinetic Energy: Energy available because of the motion of an object. 62

63. Energy: Is the capacity to do work or produce change. Potential Energy: Energy available because of the position of an object. Kinetic Energy: Energy available because of the motion of an object. Chemical Energy: The energy stored by compounds. 63

64. CHEMICAL SYMBOLS 64

65. CHEMICAL SYMBOLS Chemical symbols are shorthand notation for the names of elements. There are 118 known elements. The last several have not been named (in a conventional manner). 65

66. If an element has a single letter to represent it – the letter must be capitalized. 66

67. If an element has a single letter to represent it – the letter must be capitalized. If an element is represented by two letters – the first letter must be capitalized and the second letter must be lower case. Examples: NO is not the symbol for Nobelium – the correct symbol is No. CO is not the symbol for cobalt – the correct symbol is Co. 67

68. CHEMICAL FORMULAS A chemical formula shows the chemical composition of a compound. Three types of chemical formulas will be of interest to us. 68

69. CHEMICAL FORMULAS A chemical formula shows the chemical composition of a compound. Three types of chemical formulas will be of interest to us. 1.Molecular formulas 69

70. CHEMICAL FORMULAS A chemical formula shows the chemical composition of a compound. Three types of chemical formulas will be of interest to us. 1.Molecular formulas 2.Empirical formulas 70

71. CHEMICAL FORMULAS A chemical formula shows the chemical composition of a compound. Three types of chemical formulas will be of interest to us. 1.Molecular formulas 2.Empirical formulas 3. Structural formulas 71

72. Molecular formulas An expression showing the exact numbers and types of elements present in a molecule. 72

73. Molecular formulas An expression showing the exact numbers and types of elements present in a molecule. Example: The molecular formula for water is H 2 O – this formula tells us that a molecule of water is formed from 2 atoms of hydrogen (symbol H) 1 atom of oxygen (symbol O) The subscript 2 tells how many atoms of the element on the left of the subscript are present. 73

74. When no subscripts are present, the implied number is one. When formulas like (CH 3 ) 2 CO are encountered, the parenthesis followed by the subscript 2 mean that there are two CH 3 groups, so for the given formula, we have: 3 atoms of carbon 6 atoms of hydrogen 1 atom of oxygen 74

75. The compound Ni(CO) 4 has one atom of Ni, four atoms of carbon, and 4 atoms of oxygen. 75

76. Empirical formulas An expression showing types of elements present and the ratio of the different kinds of atoms. 76

77. Empirical formulas An expression showing types of elements present and the ratio of the different kinds of atoms. The empirical formula is useful information when the identity of an unknown compound is to be determined. 77

78. Empirical formulas An expression showing types of elements present and the ratio of the different kinds of atoms. The empirical formula is useful information when the identity of an unknown compound is to be determined. Note: Many different compounds may have the same empirical formula. 78

79. Examples: A molecule of glucose consists of 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms – and so its molecular formula is C 6 H 12 O 6. 79

80. Examples: A molecule of glucose consists of 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms – and so its molecular formula is C 6 H 12 O 6. From the formula we see that the proportion of atoms for carbon : hydrogen : oxygen is 6 : 12 : 6 or 1 : 2 : 1 The empirical formula of glucose is CH 2 O. 80

81. For many formulas, the empirical formula is the same as the molecular formula, e.g. H 2 O. 81

82. For many formulas, the empirical formula is the same as the molecular formula, e.g. H 2 O. Two examples with different molecular formulas but the same empirical formula: Benzene has the molecular formula C 6 H 6 and its empirical formula is CH. Acetylene C 2 H 2, has the empirical formula CH. 82

83. For ionic compounds, e.g. sodium chloride, the formula shows the ratio of elements that form the compound. 83

84. For ionic compounds, e.g. sodium chloride, the formula shows the ratio of elements that form the compound. Solid sodium chloride consists of a collection of positively charged sodium ions and negatively charged chloride ions in a three-dimensional structure. You cannot say which sodium ion is associated with any particular chloride ion. 84

85. For ionic compounds, e.g. sodium chloride, the formula shows the ratio of elements that form the compound. Solid sodium chloride consists of a collection of positively charged sodium ions and negatively charged chloride ions in a three-dimensional structure. You cannot say which sodium ion is associated with any particular chloride ion. The formula NaCl should be regarded as the empirical formula. 85

86. STRUCTURAL FORMULAS An expression showing the exact numbers and types of atoms present in a molecule, and information about how the atoms are chemically bonded to one another. Examples: 86 HH O water

87. 87 hydrogen peroxide H H OO

88. 88 hydrogen peroxide H H OO

89. 89 HHC H H methane

90. 90 H H C H H C H OH ethanol (ethyl alcohol)