Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Liquids and Solids Chapter 10

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<ul><li> Slide 1 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 1 Liquids and Solids Chapter 10 </li> <li> Slide 2 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 2 A phase is a homogeneous part of the system in contact with other parts of the system but separated from them by a well-defined boundary. 2 Phases Solid phase - ice Liquid phase - water </li> <li> Slide 3 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 3 H 2 O(s) H 2 O (liq)H fus = 6.02 kJ/mol H 2 O(liq) H 2 O (g)H vap = 40.7 kJ/mol </li> <li> Slide 4 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 4 Schematic representations of the three states of matter. </li> <li> Slide 5 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 5 </li> <li> Slide 6 </li> <li> 6 Intermolecular Forces Intermolecular forces are attractive forces between molecules. Intramolecular forces hold atoms together in a molecule. Intermolecular vs Intramolecular 41 kJ to vaporize 1 mole of water (inter) 930 kJ to break all O-H bonds in 1 mole of water (intra) Generally, intermolecular forces are much weaker than intramolecular forces. Measure of intermolecular force boiling point melting point H vap H fus H sub </li> <li> Slide 7 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 7 Intermolecular Forces Forces between (rather than within) molecules. dipole-dipole attraction: molecules with dipoles orient themselves so that + and ends of the dipoles are close to each other. hydrogen bonds: dipole-dipole attraction in which hydrogen is bound to a highly electronegative atom. (F, O, N) </li> <li> Slide 8 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 8 Intermolecular Forces Dipole-Dipole Forces Attractive forces between polar molecules Orientation of Polar Molecules in a Solid </li> <li> Slide 9 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 9 (a) The electrostatic interaction of two polar molecules. (b) The interaction of many dipoles in a condensed state. </li> <li> Slide 10 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 10 (a) The polar water molecule. (b) Hydrogen bonding among water molecules. </li> <li> Slide 11 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 11 </li> <li> Slide 12 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 12 Why is the hydrogen bond considered a special dipole-dipole interaction? Decreasing molar mass Decreasing boiling point Why this sudden increase? The boiling point represents the magnitude and type of bonding </li> <li> Slide 13 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 13 Intermolecular Forces Ion-Dipole Forces Attractive forces between an ion and a polar molecule Ion-Dipole Interaction </li> <li> Slide 14 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 14 London Dispersion Forces 4 relatively weak forces that exist among noble gas atoms and nonpolar molecules. (Ar, C 8 H 18 ) 4 caused by instantaneous dipole, in which electron distribution becomes asymmetrical. 4 the ease with which electron cloud of an atom can be distorted is called polarizability. </li> <li> Slide 15 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 15 (a) An instantaneous polarization can occur on atom A, creating an instantaneous dipole. This dipole creates an induced dipole on neighboring atom B. (b) Nonpolar molecules such as H2 also can develop instantaneous and induced dipoles. </li> <li> Slide 16 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 16 Intermolecular Forces Dispersion Forces Continued Polarizability is the ease with which the electron distribution in the atom or molecule can be distorted. Polarizability increases with: greater number of electrons more diffuse electron cloud Dispersion forces usually increase with molar mass. </li> <li> Slide 17 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 17 S O O What type(s) of intermolecular forces exist between each of the following molecules? HBr HBr is a polar molecule: dipole-dipole forces. There are also dispersion forces between HBr molecules. CH 4 CH 4 is nonpolar: dispersion forces. SO 2 SO 2 is a polar molecule: dipole-dipole forces. There are also dispersion forces between SO 2 molecules. </li> <li> Slide 18 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 18 Properties of Liquids Surface tension is the amount of energy required to stretch or increase the surface of a liquid by a unit area. Or The resistance to an increase in its surface area (polar molecules). Strong intermolecular forces High surface tension </li> <li> Slide 19 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 19 A molecule in the interior of a liquid is attracted by the molecules surrounding it, whereas a molecule at the surface of a liquid is attracted only by molecules below it and on each side. </li> <li> Slide 20 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 20 More Properties of Liquids Capillary Action: Spontaneous rising of a liquid in a narrow tube. Nonpolar liquid mercury forms a convex meniscus in a glass tube, whereas polar water forms a concave meniscus. </li> <li> Slide 21 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 21 More Properties of Liquids Cohesion is the intermolecular attraction between like molecules Adhesion is an attraction between unlike molecules Adhesion Cohesion </li> <li> Slide 22 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 22 More Properties of Liquids Viscosity is a measure of a fluids resistance to flow. Strong intermolecular forces High viscosity </li> <li> Slide 23 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 23 Types of Solids Crystalline Solids: highly regular arrangement of their components [table salt (NaCl), pyrite (FeS 2 )]. Amorphous solids: considerable disorder in their structures (glass). </li> <li> Slide 24 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 24 An amorphous solid does not possess a well-defined arrangement and long-range molecular order. A glass is an optically transparent fusion product of inorganic materials that has cooled to a rigid state without crystallizing Crystalline quartz (SiO 2 ) Non-crystalline quartz glass </li> <li> Slide 25 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 25 A crystalline solid possesses rigid and long-range order. In a crystalline solid, atoms, molecules or ions occupy specific (predictable) positions. An amorphous solid does not possess a well-defined arrangement and long-range molecular order. A unit cell is the basic (smallest) repeating structural unit of a crystalline solid. Unit Cell lattice point At lattice points: Atoms Molecules Ions Unit cells in 3 dimensions </li> <li> Slide 26 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 26 </li> <li> Slide 27 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 27 </li> <li> Slide 28 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 28 </li> <li> Slide 29 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 29 Shared by 8 unit cells Shared by 2 unit cells </li> <li> Slide 30 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 30 1 atom/unit cell (8 x 1/8 = 1) 2 atoms/unit cell (8 x 1/8 + 1 = 2) 4 atoms/unit cell (8 x 1/8 + 6 x 1/2 = 4) </li> <li> Slide 31 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 31 Three cubic unit cells and the corresponding lattices. </li> <li> Slide 32 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 32 </li> <li> Slide 33 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 33 Analysis of crystal structure using X-Ray Diffraction </li> <li> Slide 34 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 34 Extra distance = BC + CD = 2d sin = n (Bragg Equation) </li> <li> Slide 35 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 35 Bragg Equation Used for analysis of crystal structures. n = 2d sin d = distance between atoms n = an integer = wavelength of the x-rays </li> <li> Slide 36 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 36 X rays of wavelength 0.154 nm are diffracted from a crystal at an angle of 14.17 0. Assuming that n = 1, what is the distance (in pm) between layers in the crystal? n = 2d sin n = 1 = 14.17 0 = 0.154 nm = 154 pm d = n 2sin = 1 x 154 pm 2 x sin14.17 = 77.0 pm 11.5 </li> <li> Slide 37 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 37 Types of Crystalline Solids Ionic Solid: contains ions at the points of the lattice that describe the structure of the solid (NaCl). Molecular Solid: discrete covalently bonded molecules at each of its lattice points (sucrose, ice). </li> <li> Slide 38 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 38 Types of Crystals Ionic Crystals Lattice points occupied by cations and anions Held together by electrostatic attraction Hard, brittle, high melting point Poor conductor of heat and electricity CsClZnSCaF 2 </li> <li> Slide 39 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 39 S.Ex 10.2 Silver crystallizes in FCC closest packed structure. The radius of silver atom is 145 pm. Calculate the density of solid silver. d 2 + d 2 = (4r) 2 2d 2 =16 r 2 =16x145 2 d = 409 pm </li> <li> Slide 40 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 40 When silver crystallizes, it forms face-centered cubic cells. The unit cell edge length is 409 pm. Calculate the density of silver. d = m V V = a 3 = (409 pm) 3 = 6.83 x 10 -23 cm 3 4 atoms/unit cell in a face-centered cubic cell m = 4 Ag atoms 107.9 g mole Ag x 1 mole Ag 6.022 x 10 23 atoms x = 7.17 x 10 -22 g d = m V 7.17 x 10 -22 g 6.83 x 10 -23 cm 3 = = 10.5 g/cm 3 </li> <li> Slide 41 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 41 Types of Crystals Molecular Crystals Lattice points occupied by molecules Held together by intermolecular forces Soft, low melting point Poor conductor of heat and electricity </li> <li> Slide 42 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 42 Types of Crystals Metallic Crystals Lattice points occupied by metal atoms Held together by metallic bonds Soft to hard, low to high melting point Good conductors of heat and electricity Cross Section of a Metallic Crystal nucleus &amp; inner shell e - mobile sea of e - </li> <li> Slide 43 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 43 Examples of three types of crystalline solids. (a) An atomic solid. (b) An ionic solid. (c) A molecular solid. </li> <li> Slide 44 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 44 Types of Crystals </li> <li> Slide 45 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 45 </li> <li> Slide 46 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 46 Bonding Models for Metals Electron Sea Model: A regular array of metals in a sea of electrons. Band (Molecular Orbital) Model: Electrons assumed to travel around metal crystal in MOs formed from valence atomic orbitals of metal atoms. </li> <li> Slide 47 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 47 The electron sea model for metals postulates a regular array of cations in a "sea" of valence electrons. (a) Representation of an alkali metal (Group 1A) with one valence electron. (b) Representation of an alkaline earth metal (Group 2A) with two valence electrons. </li> <li> Slide 48 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 48 The molecular orbital energy levels produced when various numbers of atomic orbitals interact. </li> <li> Slide 49 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 49 (left) A representation of the energy levels (bands) in a magnesium crystal. (right) Crystals of magnesium grown from a vapor. </li> <li> Slide 50 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 50 Metal Alloys 1. Substitutional Alloy: some metal atoms replaced by others of similar size. brass = Cu/Zn Substances that have a mixture of elements and metallic properties. </li> <li> Slide 51 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 51 Metal Alloys (continued) 2.Interstitial Alloy: Interstices (holes) in closest packed metal structure are occupied by small atoms. steel = iron + carbon 3.Both types: Alloy steels contain a mix of substitutional (carbon) and interstitial (Cr, Mo) alloys. </li> <li> Slide 52 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 52 Two types of alloys: (a) substitutional (b) interstitial </li> <li> Slide 53 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 53 A steaming piece of dry ice CO 2 </li> <li> Slide 54 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 54 (a) Sulfur crystals (yellow) contain S 8 molecules. (b) White phosphorus (containing P 4 molecules) is so reactive with the oxygen in air that it must be stored under water. </li> <li> Slide 55 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 55 Ionic Solids Ionic solids are stable, high melting point and held ions together by stron electrostatic forces between opposite ions. Structure of most binary ionic solids (NaCl) can be explained by the closest packing of spheres Anion (large ion) packed in one of the closest packing (hcp or ccp) Cation (small ion) fits in holes among the anions. </li> <li> Slide 56 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 56 (a) The locations (gray X) of the octahedral holes in the face-centered cubic unit cell. (b) Representation of the unit cell for solid NaCl. </li> <li> Slide 57 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 57 S.Ex 10.3 Determine the net number of Na + and Cl - ions in the sodium Chloride unit cell. Cl - form closest packed FCC 8(1/8) + 6(1/2) = 4 Na + one in the center of cube, (not shared) Ones in the edge are shared by 4 unit cells; there are 12 edges; 1 + 12(1/4) = 4 1:1 stoichiometry </li> <li> Slide 58 </li> <li> Copyright2000 by Houghton Mifflin Company. All rights reserved. 58 Vapor Pressure... is the pressure of the vapor present at equilibrium.... is determined principally by the size of the intermolecular forces in the liquid.... increases significantly with temperature. Volatile liquids hav...</li></ul>

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