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A Molecular Approach, 4e - Notes for Chapter (12).doc

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Category: Chemistry
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Filename:   A Molecular Approach, 4e - Notes for Chapter (12).doc (101.5 kB)
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Chapter 12. Liquids, Solids, and Intermolecular Forces Chapter 12. Liquids, Solids, and Intermolecular Forces Chapter 12. Liquids, Solids, and Intermolecular Forces Student Objectives 12.1 Friday Night Experiments: The Discovery of Graphene Know that graphene is a single sheet of graphite. Know that graphene is in many pencil marks. 12.2 X-Ray Crystallography Recall that waves can interfere constructively and destructively. Know that X-rays diffract when interacting with the atoms in crystalline solids, forming diffraction patterns. Know that diffraction patterns can be analyzed and used to identify the three-dimensional structure of the atoms or molecules in a crystalline solid. Use Bragg’s law to calculate the relationship between the distance between crystalline layers, the wavelength of electromagnetic radiation, and the angle of reflection. 12.3 Unit Cells and Basic Structures Define and identify unit cells. Know and identify the cubic crystalline lattice types: simple, body-centered, and face-centered. Identify the kind of unit cell, the coordination number, and the edge length for the three cubic crystalline lattice types. Use the kind of unit cell and the radius of an atom to calculate the density of a metal. Identify the hexagonal and cubic closest-packing structures, and know their unit cells and component layers. 12.4 The Fundamental Types of Crystalline Solids Know the organization of crystalline solids—molecular, ionic, and atomic—including basic properties and examples. Know and identify constituent atoms, lattice types, and unit cells for some common ionic solids: CsCl, NaCl, ZnS, and CaF2. Know and identify atomic solid types—nonbonding, metallic, and network covalent—and some of their properties and examples. 12.5 The Structures of Ionic Solids Know and identify constituent atoms, lattice types, and unit cells for some common ionic solids: CsCl, NaCl, ZnS, and CaF2. Relate the concepts of the unit cells to the structures of the ionic solids. 12.6 Network Covalent Atomic Solids: Carbon and Silicates Describe the common crystalline allotropes of carbon: graphite and diamond. Know that the diamond structure is that of zinc blende. Know that carbon also forms fullerenes and nanotubes. Know that silicon and oxygen together constitute the majority of the earth’s crust. Define silicate. Know that quartz and glass have the empirical formula SiO2 but consists of tetrahedral SiO4 structural units. 12.7 Ceramics, Cement, and Glass Define ceramic. Know that silicate ceramics typically are made from clays. Know that ceramics have many applications especially in high temperatures. Know the Romans first discovered cement. Know Portland cement is a mixture of different components. Define glass. Know that there are different types of glasses. Know that the glass used in the laboratory is typically borosilicate glass. 12.8 Crystalline Solids: Band Theory Know that the organization of conduction and valence bands of molecular orbitals forms the basis for conductors, semiconductors, and insulators. 12.9 Polymers and Plastics Know that polymers are typically organic structures derived from repeating units called monomers. Know the difference between addition polymers and condensation polymers. Know the structures and repeating portions of some addition polymers and some condensation polymers. Section Summaries Lecture Outline Terms, Concepts, Relationships, Skills Figures, Tables, and Solved Examples Teaching Tips Suggestions and Examples Misconceptions and Pitfalls Lecture Outline Terms, Concepts, Relationships, Skills Figures, Tables, and Solved Examples 12.1 Friday Night Experiments: The Discovery of Graphene The discovery of a new material is described Intro figure: graphene 12.2 X-Ray Crystallography Review of constructive and destructive interference X-ray diffraction contact with atomic nuclei interaction with multiple crystal layers: constructive interference Bragg’s law n = 2d sin unnumbered figure: photo of snowflake unnumbered figure: illustration of wave interference Figure 12.1 Diffraction from a Crystal Figure 12.2 X-Ray Diffraction Analysis unnumbered figure: diffraction pattern of DNA Example 12.1 Using Bragg’s Law 12.3 Unit Cells and Basic Structures Solids and unit cells cubic structures equal edge lengths 90o angles Types of cubic lattice structures simple body-centered face-centered Lattice properties atoms per unit cell unit cell composition edge lengths density and unit cell structure Closest-packed structures hexagonal cubic unit cells and layer composition unnumbered figure: illustration of simple cubic unit cell Figure 12.3 The Seven Fundamental Types of Unit Cells Figure 12.4 The Cubic Crystalline Lattices Figure 12.5 Simple Cubic Crystal Structure Figure 12.6 Body-Centered Cubic Crystal Structure Example 12.2 Calculating the Packing Efficiency of a Unit Cell unnumbered figure: illustration of body-centered cubic unit cell Example 12.3 Relating Unit Cell Volume, Edge Length, and Atomic Radius Figure 12.7 Face-Centered Cubic Crystal Structure unnumbered figure: illustration of face-centered cubic unit cell Example 12.4 Relating Density to Crystal Structure unnumbered figures: illustrations of closest-packed structures Figure 12.8 Hexagonal Closest-Packing Crystal Structure unnumbered figures: cubic closest-packing structures Figure 12.9 Cubic Closest-Packing Crystal Structure Teaching Tips Suggestions and Examples Misconceptions and Pitfalls 12.1 Friday Night Experiments: The Discovery of Graphene This discovery illustrates how contemporary science works. Students may not understand that not all graphite is graphene and why this material is so special. 12.2 X-Ray Crystallography Layers of atoms or molecules in a crystalline solid diffract X-rays in manners that cause constructive as well as destructive interference. The diffraction patterns can be interpreted to yield information about atom distances, radii, and bond lengths. Ultimately, the structures of molecules, including large, complex molecules such as proteins, can be determined. 12.3 Unit Cells and Basic Structures Use models that can be moved and rotated to optimize students’ understanding of the cubic crystalline types. Collections of crystal structure models are viewable in CHIME and RASMOL. Cubic lattice structures have a common edge length, enabling calculations involving density, edge length, and mass. Closest-packing models are well illustrated. In particular, the layers and how they stack are shown in detail for the hexagonal and cubic closest-packed structures. Models are likely to be beneficial; for a large class, they can be placed below a document camera. Conceptual Connection 12.1 Cubic Structures Visualizing unit cells and the atoms per unit cell requires several perspectives. Closest-packed geometries are determined by how one layer of atoms is oriented with respect to the layer above and below. Lecture Outline Terms, Concepts, Relationships, Skills Figures, Tables, and Solved Examples 12.4 The Fundamental Types of Crystalline Solids Solid types and properties molecular ionic CsCl NaCl ZnS CaF2 atomic nonbonding metallic network covalent Figure 12.10 Types of Crystalline Solids unnumbered table: benzene and toluene molecular solids Chemistry in your Day Chocolate, an Edible Material Table 12.1 Crystalline Forms of Cocoa Butter Figure 12.11 Chocolate Tempering Figure 12.12 The Electron Sea Model Figure 12.13 Closest-Packed Crystal Structures in Metals Example 12.5 Classifying Crystalline Solids 12.5 The Structures of Ionic Solids The structures of: CsCl NaCl ZnS CaF2 Figure 12.14 Cesium Chloride Unit Cell Figure 12.15 Sodium Chloride Unit Cell Figure 12.16 Zinc Sulfide (Zinc Blende) Unit Cell unnumbered figure: illustration of a tetrahedral hole Figure 12.17 Calcium Fluoride Unit Cell 12.6 Network Covalent Atomic Solids: Carbon and Silicates Carbon Crystalline carbon forms graphite: planar, hexagonal diamond: tetrahedral Specialized structures: fullerenes, nanotubes, graphene Silicates Structure of SiO44 Structure of quartz Figure 12.18 Network Covalent Atomic Structures unnumbered figure: Diamond Unit Cell unnumbered figure: Zinc Blende Unit Cell Figure 12.19 C60 and a Geodesic Dome Figure 12.20 Carbon Structures Figure 12.21 SiO44 Tetrahedron Figure 12.22 Structure of Quartz Teaching Tips Suggestions and Examples Misconceptions and Pitfalls 12.4 The Fundamental Types of Crystalline Solids The taxonomy of crystalline solid types including many that are new to most students. Crystalline solids can be composed of molecules, ions, or atoms. Atomic solids can be nonbonding, metallic, or network covalent. Ionic solids and silicates are most commonly encountered previously by students. Conceptual Connection 12.2 Crystalline Solid Types and Melting Points Students may not comprehend why metals have such variable melting points. 12.5 The Structures of Ionic Solids The illustration of several common types of ionic solids Conceptual Connection 12.3 Ionic Crystalline Solid Unit Cells Students may think all structures are NaCl or simple cubic Students may not appreciate why structures such as zinc blende structure are not as strong as a diamond 12.6 Network Covalent Atomic Solids: Carbon and Silicates Conceptual Connection 12.4 Phase Changes and Pressure Students may not understand why the fullerenes are such interesting structures Students may think the SiO4 tetrahedron implies that silica has the stoichiometric radios of 1:4 and not 1:2 Lecture Outline Terms, Concepts, Relationships, Skills Figures, Tables, and Solved Examples 12.7 Ceramics, Cement, and Glass Ceramics silicate ceramics oxide ceramics nonoxide ceramics Cement Romans Portland cement Glass fused silica soda-lime glass borosilicate glass leaded glass unnumbered figure: the Venus of Dolni unnumbered figure: ceramic electrical insulator unnumbered figure: aluminum oxide crucible unnumbered figure: Pantheon unnumbered figure: glass blowing unnumbered figure: leaded glass 12.8 Crystalline Solids: Band Theory Band theory Energy levels of lithium molecules Band gap conductors: no band gap semiconductors: small band gap insulators: large band gap Doping n-type p-type p-n junctions diodes Figure 12.23 Energy Levels of Molecular Orbitals in Lithium Molecules Figure 12.24 Band Gap Table 2.2 Band gap of Group 4A elements 12.9 Polymers and Plastics Repeating units covalently bonded monomers Types addition condensation Examples polyethylene polyvinyl chloride polyurethane polyethylene terephthalate nylon unnumbered figures: space-filling models of ethylene, polyethylene Figure 12.25 Polyethylene Figure 12.26 Polyvinyl Chloride Table 12.3 Polymers of Commercial Importance Chemistry in your Day: Kevlar Teaching Tips Suggestions and Examples Misconceptions and Pitfalls 12.7 Ceramics, Cement, and Glass Explain how practical these uses of materials are and how much they effect everyday life Ask the students to imagine a world without ceramics that could handle high-temperatures or cement or glass Students may not have a practical working knowledge on how cement or glass is made Students may not understand the difference between ceramics and glass 12.8 Crystalline Solids: Band Theory The organization of MO energy levels is shown for lithium molecules. The behavior of atoms in a solid can be organized by the relationship between occupied and unoccupied orbitals. The band gap classifies the material as a conductor, semiconductor, or insulator. Conceptual Connection 12.5 Semiconductor Type Students may not understand how molecular orbitals can be formed from several atoms Students may not understand that in order for a material to conduct, the valence band needs to touch the conduction band 12.9 Polymers Polymers are ubiquitous. Many of the monomers are derived from petroleum, giving rise to concerns about price and continued availability. In part, this promotes the need or desire to recycle. The other reason for recycling is that many polymers do not readily decompose. Not all of the macroscopic properties of polymers can be easily predicted by looking at the microscopic structure. Additional Problem for Relating Density to Crystal Structure (Example 12.7) A form of iron crystallizes with a body-centered unit cell. The radius of iron is 124 pm. Calculate the density of this form of iron in g/cm3. Sort You are given the radius of an iron atom and its crystal structure. You are asked to find the density of solid iron. Given r = 124 pm, body-centered cubic Find d Strategize The conceptual plan is based on the definition of density. For a body-centered cubic unit cell, the atoms touch along the center diagonal. The cell length can be derived in terms of the atom radius. Conceptual Plan l = 4r / 3 V = l3 [volume of a cube with a length of l] m = mass of unit cell = number of atoms in unit cell x mass of each atom d = m / V Solve First, find the length of the unit cell using the equations relating the length to the radius of an atom in the body-centered cell. Second, convert the length to a volume by cubing the value. Find the mass of the iron atoms in the cell. The body- centered cell contains two iron atoms. Use the molar mass and Avogadro’s number to find the mass of each atom. The density is the mass divided by the volume. Compute the value. Solution l = 4r / 3 = 4 1.24 10?8 cm / 1.73 = 2.87 10?8 cm V = l3 = 23.6 1024 cm3 Check The units (g) are correct. The magnitude of the answer (7.84) seems to make physical sense. 170 Copyright © 2017 by Education, Inc. 169 Copyright © 2017 by Education, Inc.

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