LECTURE 7.2LECTURE 7.2

LECTURE OUTLINELECTURE OUTLINE

Weekly ReadingWeekly ReadingLesson 07 Prototype Quiz: FeedbackLesson 07 Prototype Quiz: Feedback

CHAPTER XXII: AMORPHOUS CHAPTER XXII: AMORPHOUS SOLIDSSOLIDS

Chapter 22 reintroduces a class of materials Chapter 22 reintroduces a class of materials called “amorphous,” or without form. called “amorphous,” or without form. Amorphous materials are non-crystalline—the Amorphous materials are non-crystalline—the atoms/monomers/molecules are not arranged atoms/monomers/molecules are not arranged in a periodic fashion. The concepts of short-in a periodic fashion. The concepts of short-range order and long-range order are range order and long-range order are introduced as an aid in distinguishing between introduced as an aid in distinguishing between a silicate crystal and a silicate glass.a silicate crystal and a silicate glass.

CHAPTER XXIII: SYMMETRY IN CHAPTER XXIII: SYMMETRY IN ART, NATURE, AND SCIENCEART, NATURE, AND SCIENCE

Mankind has been fascinated by symmetry since the Mankind has been fascinated by symmetry since the dawn of time. The relationship between left and right-dawn of time. The relationship between left and right-handedness, the distribution of petals on a flower head, handedness, the distribution of petals on a flower head, and many Paleolithic cave paintings deal with concepts of and many Paleolithic cave paintings deal with concepts of symmetry. In Chapter 23, the reader is introduced to the symmetry. In Chapter 23, the reader is introduced to the major classes of symmetry, yet the goal is to describe in major classes of symmetry, yet the goal is to describe in uncomplicated terms the symmetries that are displayed by uncomplicated terms the symmetries that are displayed by crystalline solids. The “form,” which has been described crystalline solids. The “form,” which has been described in numerous earlier chapters, is seen to be synonymous in numerous earlier chapters, is seen to be synonymous with the “lattice,” which is used to describe the with the “lattice,” which is used to describe the translational symmetry of crystalline materials.translational symmetry of crystalline materials.

CHAPTER XXIV: THE CHAPTER XXIV: THE MICROSTRUCTURE OF MICROSTRUCTURE OF

MATERIALSMATERIALS Chapter 24 is mostly a summary of previously presented Chapter 24 is mostly a summary of previously presented

“microstructures.” The term “microstructure” is used to “microstructures.” The term “microstructure” is used to describe level(s) of structure amenable to study using the describe level(s) of structure amenable to study using the light microscope (traditionally) and the electron light microscope (traditionally) and the electron microscope (more recently).microscope (more recently).

Two “case studies” of the microstructures of materials Two “case studies” of the microstructures of materials are presented:are presented: The microstructural studies of Rene-Antoine Ferchault de The microstructural studies of Rene-Antoine Ferchault de

Reaumur.Reaumur. The microstructure of a naturally occurring composite: granite.The microstructure of a naturally occurring composite: granite.

PART D: EPILOGUEPART D: EPILOGUE This book has it all: preambles, prologues, and even This book has it all: preambles, prologues, and even

epilogues! This epilogue is important because it epilogues! This epilogue is important because it serves as an “executive summary” for the preceding serves as an “executive summary” for the preceding thirteen chapters. It provides unifying themes by thirteen chapters. It provides unifying themes by classifying solid materials by their bond types, classifying solid materials by their bond types, relating the nature of the monomer to the material relating the nature of the monomer to the material classification, and summarizing the various states of classification, and summarizing the various states of matter—a process that we first began in Chapter 13. matter—a process that we first began in Chapter 13. The epilogue finishes with a discussion of the The epilogue finishes with a discussion of the packing fraction” and “specific gravity” of materials, packing fraction” and “specific gravity” of materials, as they are affected by bond type. This latter as they are affected by bond type. This latter discussion is somewhat convoluted but merits some discussion is somewhat convoluted but merits some thought and attention!thought and attention!

PRACTICE QUIZ #7: PRACTICE QUIZ #7: FEEDBACKFEEDBACK

UNIT 7 QUIZAverage : 53%

-80

-60

-40

-20

0

20

40

60

80

100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

% Correct Answers Discrimination

Q2. The intermolecular bonding in solid bromine is_____.<a> covalent<b> ionic<c+> van der Waals<d> hydrogen<e> not applicable<F> Reference to Figure 1 shows that bromine is in Group VII and is a non-metal. Bromine may only form one bonding pair, and Br forms a diatomic molecule. Within the molecule, the bonding (intramolecular) is covalent. Between the molecules, the bonding (intermolecular) is van der Waals.

a

24 Mg12

23

45

67

7 Li39 Be4

23 Na1139 K19

1 H1

40 Ca2045 Sc21

48 Ti2251 V23

52 Cr2455 Mn25

56 Fe2659 Co27

59 Ni2864 Cu29

65 Zn30

4 He211 B5

12 C614 N7

16 O819 F9

20 Ne1027 Al13

28 Si1431 P15

32 S1635 Cl17

40 Ar1870 Ga31

73 Ge3275 As33

79 Se3480 Br35

84 Kr3685 Rb37

89 Y3991 Zr40

93 Nb4196 Mo42

98 Tc43101 Ru44

103 Rh45106 Pd46

108 Ag47112 Cd48

115 In49119 Sn50

122 Sb51128 Te52

127 I53131 Xe54

133 Cs55137 Ba56

139 La57178 Hf72

181 Ta73181 W74

186 Re75190 Os76

192 Ir77195 Pt78

197 Au79201 Hg80

204 Tl81207 Pb82

209 Bi83210 Po84

210 At85222 Rn86

223 Fr87226 Ra88

227 Ac89261 Ku104

262 Ha105

II IIIIVVVIVIIVIII

I

88 Sr38

Q5. The intermolecular bonding in iridium is ______.<a> covalent<b> ionic<c> van der Waals<d> hydrogen<e+> not applicable<F>The answer is “not applicable.” The differentiation between intramolecular and intermolecular bonding only has meaning for covalently bonded molecular materials. Iridium is a metal!

a

24 Mg12

23

45

67

7 Li39 Be4

23 Na1139 K19

1 H1

40 Ca2045 Sc21

48 Ti2251 V23

52 Cr2455 Mn25

56 Fe2659 Co27

59 Ni2864 Cu29

65 Zn30

4 He211 B5

12 C614 N7

16 O819 F9

20 Ne1027 Al13

28 Si1431 P15

32 S1635 Cl17

40 Ar1870 Ga31

73 Ge3275 As33

79 Se3480 Br35

84 Kr3685 Rb37

89 Y3991 Zr40

93 Nb4196 Mo42

98 Tc43101 Ru44

103 Rh45106 Pd46

108 Ag47112 Cd48

115 In49119 Sn50

122 Sb51128 Te52

127 I53131 Xe54

133 Cs55137 Ba56

139 La57178 Hf72

181 Ta73181 W74

186 Re75190 Os76

192 Ir77195 Pt78

197 Au79201 Hg80

204 Tl81207 Pb82

209 Bi83210 Po84

210 At85222 Rn86

223 Fr87226 Ra88

227 Ac89261 Ku104

262 Ha105

II IIIIVVVIVIIVIII

I

88 Sr38

Q7. Figure 2 (next slide) shows a cubic form that contains a silicon atom at the center of the cube and an oxygen atom at one of the corners. A silica tetrahedron could be completed by assigning ________.<a+> oxygen atoms to positions 1, 5, 7 <b> silicon atoms to positions 1, 5, 7<c> oxygen atoms to positions 1, 7, 8<d> silicon atoms to positions 1, 7, 8<e> oxygen atoms to positions 1, 2, 4

Figure 2Figure 2

a

1 2

34

5

67

8

<F> Oxygen atoms to positions 1, 5, 7 (and see Figure 2). This creates the “two-up, two-down” bonding characteristic of a tetrahedron.

Q8. Figure 3 (next slide) plots the energy (as heat) in calories required to raise the temperature of a fixed mass of water from –50˚C to a temperature in excess of 100˚C. The energy required to raise the temperature of the solid water (ice) from –50˚C to -5˚C is needed to ________.

<a+> increase the vibrational energy associated with the intermolecular and intramolecular bonds within the ice-lattice <b> break some of the hydrogen bonds between the water molecule <c> break some of the covalent bonds between hydrogen and oxygen<d> break all of the hydrogen bonds between the water molecules <e> break all of the covalent bonds between hydrogen and oxygen

a

Temperature(˚C)

Heat Subtracted or Added (calories)20 100 200 700740-50

050100150

Ice

Water

Vapor

<F> Increasing the temperature of crystalline ice from –50˚C to –5˚C results in no change in state, and the increase in thermal energy will be manifested in an increased vibrational energy of both the covalent and the hydrogen bonds. The breaking of hydrogen bonds will occur on melting and on vaporization, but will not occur during heating in the solid state. The breaking of the covalent bonds is much more difficult than the breaking of hydrogen bonds and will not occur during melting nor during vaporization. Very high temperatures will be required before the covalent bonds are disrupted.

Q12. Figure 5 (next slide) shows the “heat of fusion” for several “molecular liquids.” The heat of fusion is the heat required to convert a given mass of solid to a liquid. Water has a much higher heat of fusion than the other liquids because ___________.<a+> the molecules in water are hydrogen bonded to each other, whereas the other molecules are bonded only by van der Waals forces<b> the organic molecules (carbon tetrachloride, acetone, benzene, and ethyl alcohol) are ionically bonded, whereas the intramolecular bonding in water is covalent<c> The organic molecules form “glasses” on slow cooling<d> the intermolecular bonding in water is covalent<e> the intramolecular bonding in water is covalent

Figure 5Figure 5

a

Carbon TetrachlorideAcetoneBenzeneEthyl AlcoholWater0

20406080100Heat of Fusion

Liquid

Heat ofFusion

<F> The intermolecular bonding in water is “hydrogen.” In the other liquids it is van der Waals only. Hence, it takes more energy to break the hydrogen bonds as opposed to the van der Waals bonds.

Q17. Bromine (Br) is in Group VII and forms two bonding pairs.

<a> True

<b+> False

<F> False. Bromine is in Group VII and may only form a single bonding pair.

a

24 Mg12

23

45

67

7 Li39 Be4

23 Na1139 K19

1 H1

40 Ca2045 Sc21

48 Ti2251 V23

52 Cr2455 Mn25

56 Fe2659 Co27

59 Ni2864 Cu29

65 Zn30

4 He211 B5

12 C614 N7

16 O819 F9

20 Ne1027 Al13

28 Si1431 P15

32 S1635 Cl17

40 Ar1870 Ga31

73 Ge3275 As33

79 Se3480 Br35

84 Kr3685 Rb37

89 Y3991 Zr40

93 Nb4196 Mo42

98 Tc43101 Ru44

103 Rh45106 Pd46

108 Ag47112 Cd48

115 In49119 Sn50

122 Sb51128 Te52

127 I53131 Xe54

133 Cs55137 Ba56

139 La57178 Hf72

181 Ta73181 W74

186 Re75190 Os76

192 Ir77195 Pt78

197 Au79201 Hg80

204 Tl81207 Pb82

209 Bi83210 Po84

210 At85222 Rn86

223 Fr87226 Ra88

227 Ac89261 Ku104

262 Ha105

II IIIIVVVIVIIVIII

I

88 Sr38

Q19. Arsenic is a __________.<a> noble gas<b> semiconductor<c> metal<d+> non-metal<e> polymer<F> Arsenic is in Group V (Figure 14.17) and is a non-metal.

a

24 Mg12

23

45

67

7 Li39 Be4

23 Na1139 K19

1 H1

40 Ca2045 Sc21

48 Ti2251 V23

52 Cr2455 Mn25

56 Fe2659 Co27

59 Ni2864 Cu29

65 Zn30

4 He211 B5

12 C614 N7

16 O819 F9

20 Ne1027 Al13

28 Si1431 P15

32 S1635 Cl17

40 Ar1870 Ga31

73 Ge3275 As33

79 Se3480 Br35

84 Kr3685 Rb37

89 Y3991 Zr40

93 Nb4196 Mo42

98 Tc43101 Ru44

103 Rh45106 Pd46

108 Ag47112 Cd48

115 In49119 Sn50

122 Sb51128 Te52

127 I53131 Xe54

133 Cs55137 Ba56

139 La57178 Hf72

181 Ta73181 W74

186 Re75190 Os76

192 Ir77195 Pt78

197 Au79201 Hg80

204 Tl81207 Pb82

209 Bi83210 Po84

210 At85222 Rn86

223 Fr87226 Ra88

227 Ac89261 Ku104

262 Ha105

II IIIIVVVIVIIVIII

I

88 Sr38

Q22. Vulcanized rubber is a ________.

<a+> thermoset

<b> crystalline thermoplastic

<c> amorphous thermoplastic

<F> Vulcanized rubber is cross-linked. It is a thermoset (Figure 20.8).

Q24. Polytetrafluoroethylene (PTFE) is a _____.

<a> metallically bonded solid

<b> ionically bonded solid

<c> covalently bonded network solid

<d> covalently bonded molecular solid

<e+> macromolecule/polymer

<F> It is a macromolecule/polymer.