Welcome to General Chemistry I

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1 Welcome to General Chemistry I

2 Chemistry Chemistry is a branch of science that studies the composition and properties of matter and the changes it undergoes H 2 O 2

3 CLASSIFICATION OF MATTER 3

4 Matter Matter is anything that has mass and takes up space 4

5 States of Matter The three states of matter are 1) solid 2) liquid 3) gas In this figure, those states are ice, liquid water, and water vapor 5

6 States of Matter 6

7 Classification of Matter by Composition 7

8 Classification of Matter by Composition 8

Classification of Matter by Composition Heterogeneous mixture Heterogeneous Has two or more visibly distinct phases Each phase has different properties Mixture contains two or more

9 Classification of Matter by Composition Heterogeneous mixture Heterogeneous Has two or more visibly distinct phases Each phase has different properties Mixture contains two or more substances that are mixed together contain substances that have not reacted chemically with each other Can be separated by physical methods 9

10 Classification of Matter by Composition 10

11 Classification of Matter by Composition Milk is a liquid with bits of solid particles floating around; if you let it sit, the particles will separate. 11

12 Classification of Matter by Composition Homogeneous mixture Homogeneous Contains one visible distinct phase Contains uniform properties throughout Mixture contains two or more substances that are mixed together contain substances that have not reacted chemically with each other Can be separated by physical methods 12

13 Classification of Matter by Composition 13

14 Classification of Matter by Composition Pure substance made up of one type of particle Particle of water is H 2 O ( a compound) Particle of gold is Au (an element) 14

15 Classification of Matter by Composition 15

16 Classification of Matter by Composition Element Pure substance that can not be broken down into two or more pure substances 16

17 Classification of Matter by Composition 17

18 Classification of Matter by Composition Compound Pure substance that can be broken down into two or more pure substances 18

19 Methods of Classification of Matter 1. State of Matter A. Solid B. Liquid C. Gas 2. Composition of Matter A. Element B. Compound C. Mixture 19

20 PROPERTIES OF MATTER 20

21 Types of Changes Physical Changes Chemical Changes 21

22 Types of Changes Physical Changes are changes in matter that do not change the composition of a substance Examples include changes of state, temperature, and volume 22

23 Types of Changes Converting between the three states of matter is a physical change When ice melts or water evaporates, there are still 2 Hydrogen Why? atoms and 1 Oxygen atom in each molecule 23

24 Types of Changes Converting between the three states of matter is a physical change When ice melts or water evaporates, there are still 2 Hydrogen atoms and 1 Oxygen atom in each molecule 24

25 Types of Changes Physical Changes are changes in matter that do not change the composition of a substance Examples include changes of state, temperature, and volume Chemical Changes result in new substances Examples include combustion, oxidation, and decomposition 25

26 Types of Changes A chemical reaction is a chemical change Elements hydrogen and oxygen become water 26

27 Standardized system of measurement, based on decimal notation METRIC SYSTEM OF UNITS 27

28 Measurements Observations may be: Qualitative Quantitative 28

29 Quantitative (Numerical) Data Obtained by measurement Length Volume Mass 29

30 Metric System: Base Units Table 1.4 on page 14 lists base units Length meter (m) Volume Mass kilogram (kg) 30

31 Metric System of Units: Prefixes Table 1.5 on page 14 31

32 Metric System of Units: Prefixes 32

33 Metric System of Units: Prefixes 1 m 10 cm 1 cm 1 mm 100 mm 10 mm 1 mm 100 nm 10 nm 1 nm 0.1 nm 33

34 Metric System: Base Units Table 1.4 on page 14 lists base units Length meter (m) Volume? Mass kilogram (kg) 34

35 Metric System: Derived Base Units Volume Derived Unit Base unit liter (L) 1 dm 3 = 1 L 1 cm 3 = 1 ml Volume Liter (L) 35

36 Metric System: Derived Base Units Density is the amount of mass that fills a space less dense more dense 36

37 Density Density is the amount of mass that fills a space Derived Unit Expressed as g/ml or g/cm 3 Temperature dependent 37

38 Density Density is the amount of mass that fills a space Calculate density of mercury if 1.00 x 10 2 g occupies 7.36 cm 3 mass = 1.00 x 10 2 g volume = 7.36 cm 3 38

39 UNCERTAINTY IN MEASUREMENT 39

40 Quantitative (Numerical) Data Obtained by measurement Length Volume Mass 40

41 Quantitative (Numerical) Data Measurement is inexact, which leads to uncertainty Length Volume Mass 41

42 Measurements: Uncertainty Uncertainty is degree of doubt about reading Only record one estimated (uncertain) digit in a measurement 29.2 => =>

43 Measurements: Significant Figures Digits in a measurement that are known to a certainty plus one that is estimated (uncertain) All certain digits + One uncertain digit # of Significant Figures

44 Measurements Precise: measurements are closely cluster about a single value Accurate: measurements clustered around true value 44

45 Measurements Precise: measurements are closely cluster about a single value Accurate: measurements clustered around true value 45

46 DETERMINING SIGNIFICANT FIGURES 46

47 Significant Figures Rule 1: Digits 1 9 are always significant figures 47

48 Significant Figures Rule 1: Digits 1 9 are always significant figures How many significant figures in the numbers below?

49 Significant Figures Rule 2: Zeros at the beginning of a number are not significant 49

50 Significant Figures Rule 2: Zeros at the beginning of a number are not significant How many significant figures in the numbers below?

51 Significant Figures Rule 3: Zeros in-between nonzero digits are significant figures 51

52 Significant Figures Rule 3: Zeros in-between nonzero digits are significant figures How many significant figures in the numbers below?

53 Significant Figures Rule 4: Zeros at a end of a number are only significant if there is a decimal point in number 53

54 Significant Figures Rule 4: Zeros at a end of a number are only significant if there is a decimal point in number How many significant figures in the numbers below?

55 Mathematical operations should not increase or decrease uncertainty of measurements SIGNIFICANT FIGURES AND MATHEMATICAL OPERATIONS 55

56 Operational Rules for Mathematical Operations Rule 1: In multiplication and division operations, the number of significant figures in the answer is the same as the number in the calculation with the fewest significant digits x 1.2 = (calculator answer) = 2.9 (correct answer) 56

57 Operational Rules for Mathematical Operations Rule 2: In addition and subtraction operations, number of decimal places in answer is equal to number with fewest decimal places 2546 Ones Position thousandth position hundredth position

58 Operational Rules for Mathematical Operations Exact numbers contain no uncertainty; do not apply significant figures to them Counted numbers (number of eggs in a dozen) Simple fractions (1/4) Always round the answer to the correct number of significant digits 58

59 Rounding off numbers Process of deleting unwanted digits Rule 1: In a series of calculations, carry the extra digits through to the final result, then round Rule 2: If the first digit to be dropped is less than 5, that digit and all that follow are dropped rounded to 3 significant figures is

60 Rounding off numbers Process of deleting unwanted digits Rule 3: If the first digit to be dropped is equal to or greater than 5 the last retained digit increased by rounded to 3 significant figures is

61 DIMENSIONAL ANALYSIS 61

62 Dimensional Analysis: Conversion Factors Conversion Factor A ratio (or fraction) which represents the relationship between two different units 1 min = 60 sec It is ALWAYS equal to 1 Allows you to change units while maintaining your original measurements 62

63 Mathematical Operations: Conversion Factors Conversion Factor A ratio (or fraction) which represents the relationship between two different units 1 min = 60 sec It is ALWAYS equal to 1 1 min= 60 sec 1 min= 1 60 sec 60 sec 60 sec Allows you to change units while maintaining your original measurements 63

64 Mathematical Operations: Conversion Factors Conversion Factor A ratio (or fraction) which represents the relationship between two different units 1 min = 60 sec It is ALWAYS equal to 1 1 min= 60 sec 1 min = 1 60 sec 60 sec 60 sec Allows you to change units while maintaining your original measurements 64

65 Dimensional Analysis Procedure for converting a measurement in one unit to an equivalent measurement in another unit Step 1: Identify known/given unit and unit desired given unit desired unit Step 2: Multiply known/given unit by conversion factor(s) to get the desired unit Step 3: Check that all unwanted units cancel out and result have correct number of significant figures 65

66 Dimensional Analysis Single Conversion Step 1: convert inches to centimeters Step 2: Is the conversion a. Metric-to-Metric b. English-to-English c. English-to-Metric d. Metric-to-English Given unit Desired unit 66

67 Dimensional Analysis Procedure for converting a measurement in one unit to an equivalent measurement in another unit Step 1: Identify known/given unit and unit desired given unit desired unit Step 2: Multiply known/given unit by conversion factor(s) to get the desired unit x Step 3: Check that all unwanted units cancel out and result have correct number of significant figures Conversion Factor 67

68 Dimensional Analysis Single Conversion Step 1: convert inches to centimeters Step 2: Is the conversion a. Metric-to-Metric b. English-to-English c. English-to-Metric d. Metric-to-English Given unit Desired unit 68

69 Dimensional Analysis Single Conversion Step 1: convert inches to centimeters Step 2: Is the conversion a. Metric-to-Metric b. English-to-English c. English-to-Metric d. Metric-to-English Given unit Desired unit 69

70 Dimensional Analysis Procedure for converting a measurement in one unit to an equivalent measurement in another unit Step 1: Identify known/given unit and unit desired given unit desired unit Step 2: Multiply known/given unit by conversion factor(s) to get the desired unit x Step 3: Check that all unwanted units cancel out and result have correct number of significant figures x 70

71 Dimensional Analysis Single Conversion Step 1: convert inches to centimeters Step 3: Given unit Desired unit Is the conversion factor exact or not exact? 71

72 Dimensional Analysis Single Conversion Step 1: convert inches to centimeters Step 3: Given unit Desired unit Is the conversion factor exact or not exact? 72

73 Dimensional Analysis Single Conversion Step 1: convert inches to centimeters Step 3: Given unit Desired unit Is the conversion factor exact or not exact? 73

74 Dimensional Analysis Procedure for converting a measurement in one unit to an equivalent measurement in another unit Step 1: Identify known/given unit and unit desired given unit desired unit Step 2: Multiply known/given unit by conversion factor(s) to get the desired unit 74

75 Dimensional Analysis Two Conversions Step 1: convert millimeters to centimeters Step 2: Is the conversion a. Metric-to-Metric b. English-to-English c. English-to-Metric d. Metric-to-English Given unit Desired unit 75

76 Dimensional Analysis Procedure for converting a measurement in one unit to an equivalent measurement in another unit Step 1: Identify known/given unit and unit desired given unit desired unit Step 2: Multiply known/given unit by conversion factor(s) to get the desired unit x 76

77 Dimensional Analysis Two Conversions Step 1: convert millimeters to centimeters Step 2: Is the conversion a. Metric-to-Metric b. English-to-English c. English-to-Metric d. Metric-to-English Given unit Desired unit 77

78 Dimensional Analysis Two Conversions Step 1: convert millimeters to centimeters Step 2: Is the conversion a. Metric-to-Metric b. English-to-English c. English-to-Metric d. Metric-to-English Given unit Desired unit 78

79 Dimensional Analysis Two Conversions Step 1: convert millimeters to centimeters Step 2: Is the conversion a. Metric-to-Metric b. English-to-English c. English-to-Metric d. Metric-to-English Given unit Desired unit 79

80 Dimensional Analysis Procedure for converting a measurement in one unit to an equivalent measurement in another unit Step 3: Check that all unwanted units cancel out and result have correct number of significant figures x 80

81 Dimensional Analysis Two Conversions Step 1: convert millimeters to centimeters Step 3: Given unit Desired unit Is the conversion factor exact or not exact? 81

82 Dimensional Analysis Two Conversions Step 1: convert millimeters to centimeters Step 3: Given unit Desired unit Is the conversion factor exact or not exact? 82

83 Dimensional Analysis Two Conversions Step 1: convert millimeters to centimeters Step 3: Given unit Desired unit Is the conversion factor exact or not exact? 83

84 Calculate volume of 65.0 g of wood alcohol if the density is g/ml This is a dimensional analysis 84

85 Dimensional Analysis Procedure for converting a measurement in one unit to an equivalent measurement in another unit Step 1: Identify known/given unit and unit desired given unit desired unit Step 2: Multiply known/given unit by conversion factor(s) to get the desired unit x Step 3: Check that all unwanted units cancel out and result have correct number of significant figures x 85

86 Calculate volume of 65.0 g of wood alcohol if the density is g/ml Step 1: g/ml, ml and g 86

87 Calculate volume of 65.0 g of wood alcohol if the density is g/ml Step 1: g/ml, ml and g Given unit Desired unit What is the conversion factor? 87

88 Calculate volume of 65.0 g of wood alcohol if the density is g/ml Step 1: g/ml, ml and g Step 2: Step 3:??? 88

89 Calculate volume of 65.0 g of wood alcohol if the density is g/ml Step 1: g/ml, ml and g Step 2: Step 3: 89

90 What is the mass in grams of a cube of gold (d = g/cm 3 ) if the length of the cube is 2.00 cm? Step 1: g, cm and g/cm

91 What is the mass in grams of a cube of gold (d = g/cm 3 ) if the length of the cube is 2.00 cm? Step 1: g, cm and g/cm 3 Given unit Desired unit What is the conversion factor? 91

92 What is the mass in grams of a cube of gold (d = g/cm 3 ) if the length of the cube is 2.00 cm? Step 1: g, cm and g/cm 3 Step 2: 2.00 cm Step 3:??? 92

93 What is the mass in grams of a cube of gold (d = g/cm 3 ) if the length of the cube is 2.00 cm? Step 1: g, cm and g/cm 3 Step 2: 2.00 cm Step 3: 93

94 TEMPERATURE 94

95 Temperature Measures the heat or lack of heat in an object 3 different temperature scales Celsius o C = 5/9( o F - 32) o C = K Kelvin K = o C Fahrenheit o F = (9/5) o C

96 Temperature Measures the heat or lack of heat in an object 3 different temperature scales Celsius o C = 5/9( o F - 32) o C = K Kelvin K = o C Fahrenheit o F = (9/5) o C + 32 If a weather forecaster predicts that the temperature for the day will reach 31 o C, what is the predicted temperature in o F? 96

97 Temperature Measures the heat or lack of heat in an object 3 different temperature scales Celsius o C = 5/9( o F - 32) o C = K Kelvin K = o C Fahrenheit o F = (9/5) o C + 32 If a weather forecaster predicts that the temperature for the day will reach 31 o C, what is the predicted temperature in K? K = = 304K 97

98 98

Lecture Presentation. Chapter 1. Introduction: Matter and Measurement. James F. Kirby Quinnipiac University Hamden, CT

Lecture Presentation. Chapter 1. Introduction: Matter and Measurement. James F. Kirby Quinnipiac University Hamden, CT Lecture Presentation Chapter 1 Introduction: Matter and Measurement James F. Kirby Quinnipiac University Hamden, CT Why do we study chemistry? My parents want me to study chemistry. I need to graduate.