Zumdahl De Coste World of CHEMISTRY Chapter 14

Zumdahl De. Coste World of CHEMISTRY

Chapter 14 Liquids and Solids Copyright© by Houghton Mifflin Company. All rights reserved.

Figure 14. 1: Representations of the gas, liquid, and solid states. Solid and liquid states more similar than liquid and gaseous states Copyright© by Houghton Mifflin Company. All rights reserved. 3

Intermolecular Forces Explain why water is liquid at normal temperature and pressure l Forces that occur between molecules l – Dipole-dipole attraction l l 1% as strong as bonds Weaken as distance increases – Hydrogen bonding (type of dipole-dipole force) l Hydrogen bound to highly electronegative atom – London dispersion forces l l l Exist in noble gases and nonpolar molecules Temporary dipole moments form producing attraction Intramolecular forces: forces within molecule itself (bonds) Copyright© by Houghton Mifflin Company. All rights reserved. 4

Figure 14. 2: Intermolecular forces exist between molecules. Bonds exist within molecules. Copyright© by Houghton Mifflin Company. All rights reserved. 5

Figure 14. 3: (a) Interaction of two polar molecules. (b) Interaction of many dipoles in a liquid. Copyright© by Houghton Mifflin Company. All rights reserved. 6

Figure 14. 4: Polar water molecules. Copyright© by Houghton Mifflin Company. All rights reserved. 7

Figure 14. 4: Hydrogen bonding among water molecules. Copyright© by Houghton Mifflin Company. All rights reserved. 8

Figure 14. 5: The boiling points of covalent hydrides. Copyright© by Houghton Mifflin Company. All rights reserved. 9

Figure 14. 6: Atoms with spherical electron probability. Copyright© by Houghton Mifflin Company. All rights reserved. 10

14. 6: The atom on the left develops an instantaneous dipole. Copyright© by Houghton Mifflin Company. All rights reserved. 11

Figure 14. 6: Instantaneous dipole on A induces a dipole on B. Copyright© by Houghton Mifflin Company. All rights reserved. 12

Water and Its Phase Changes l Normal boiling point of water = 100°C at pressure = 1 atm l Normal freezing point of water = 0°C at pressure = 1 atm Copyright© by Houghton Mifflin Company. All rights reserved. 13

Figure 14. 7: The heating/cooling curve for water heated or cooled at a constant rate. Copyright© by Houghton Mifflin Company. All rights reserved. 14

Energy Requirements for Change of State l Extra energy needed to change state (solid to liquid, liquid to vapor) – need to overcome intermolecular forces l Molar heat of fusion (water) = 6. 02 k. J/mol l Molar heat of vaporization = 40. 6 k. J/mol Copyright© by Houghton Mifflin Company. All rights reserved. 15

Figure 14. 8: Both liquid water and gaseous water contain H 2 O molecules. Copyright© by Houghton Mifflin Company. All rights reserved. 16

Evaporation and Vapor Pressure l l l Evaporation/vaporization: requires energy to overcome intermolecular forces Endothermic process Condensation: vapor molecules form a liquid Eventually (in closed container) the rate of vaporization = rate of condensation; system is in equilibrium Molecules are still vaporizing/condensing, but there is no net change because they balance each other out Copyright© by Houghton Mifflin Company. All rights reserved. 17

Figure 14. 9: Microscopic view of a liquid near its surface. Copyright© by Houghton Mifflin Company. All rights reserved. 18

Figure 14. 10: Behavior of a liquid in a closed container. Copyright© by Houghton Mifflin Company. All rights reserved. 19

Figure 14. 11: (a) Measuring vapor of a liquid by using a simple barometer. (b) The water vapor pushed the mercury level down. (c) Diethyl ether shows a higher vapor pressure than water. Copyright© by Houghton Mifflin Company. All rights reserved. 20

Vapor Pressure l Liquids with high vapor pressures are said to be volatile: they evaporate rapidly l Determined by intermolecular forces – Large intermolecular forces = low vapor pressure Copyright© by Houghton Mifflin Company. All rights reserved. 21

Figure 14. 12: Water rapidly boiling on a stove. Bubbles form on interior of liquid, then rise to surface and POP! Copyright© by Houghton Mifflin Company. All rights reserved. 22

Figure 14. 13: Bubble expands as H 2 O molecules enter. • Vapor pressure must equal atmospheric pressure for boiling to occur • Bubbles must have enough energy to sustain pressure in bubble • Boiling point decreases with altitude because atmospheric pressure is less Copyright© by Houghton Mifflin Company. All rights reserved. 23

Figure 14. 14: The formation of the bubble is opposed by atmospheric pressure. Copyright© by Houghton Mifflin Company. All rights reserved. 24

Types of Solids l Crystalline solids: have regular arrangements of their components – highly ordered arrangement produces beautiful, regularly shaped crystals Copyright© by Houghton Mifflin Company. All rights reserved. 25

Figure 14. 15: Sodium and chloride ions. Copyright© by Houghton Mifflin Company. All rights reserved. 26

Figure 14. 17: The classes of crystalline solids. Copyright© by Houghton Mifflin Company. All rights reserved. 27

Figure 14. 18: Molecular representation of diamond. Atomic Solid Copyright© by Houghton Mifflin Company. All rights reserved. 28

Figure 14. 18: Molecular representation of sodium chloride. Ionic Solid Copyright© by Houghton Mifflin Company. All rights reserved. 29

Figure 14. 18: A molecular solid. Molecular solid Copyright© by Houghton Mifflin Company. All rights reserved. 30

Bonding in Solids Copyright© by Houghton Mifflin Company. All rights reserved. 31

Figure 14. 19: The packing of Cl¯ and Na+ ions in solid sodium chloride. Ionic Solids: • Stable • High melting points • Held together by strong forces • Spheres packed together as efficiently as possible Copyright© by Houghton Mifflin Company. All rights reserved. 32

Figure 14. 21: A representation of part of the structure of solid phosphorus. Molecular Solids: • Fundamental particle is a molecule • Relatively low melting points – weak intermolecular forces • Either dipole-dipole or London forces • Bonds between atoms stronger than bonds between molecules Copyright© by Houghton Mifflin Company. All rights reserved. 33

Atomic Solids l Properties vary greatly because of different ways fundamental particles interact with each other – Group 8: low melting points, filled shells, weak London dispersion forces – Diamond: one of hardest substances known, extremely high melting point, very strong covalent carbon-carbon bonds Copyright© by Houghton Mifflin Company. All rights reserved. 34

Bonding in Metals l Shape can be changed easily, but durable with high melting points l Bonding is strong but nondirectional l Electron sea model: array of metal atoms in a “sea” of valence electrons that are shared among the atoms – Electrons can conduct heat and electricity and atoms can move easily Copyright© by Houghton Mifflin Company. All rights reserved. 35

Alloys Alloy: substance that contains a mixture of elements and has metallic properties Because of nature of metallic crystal, other substances can be easily introduced Copyright© by Houghton Mifflin Company. All rights reserved. 36

Figure 14. 22: Molecular representation of brass. Substitutional alloy: some of the host metal atoms are replaced by other metal atoms of similar sizes Copyright© by Houghton Mifflin Company. All rights reserved. 37

Figure 14. 22: Molecular representation of steel. Interstitial alloy: holes among the closely packed metal atoms are occupied by atoms much smaller than the host atoms Copyright© by Houghton Mifflin Company. All rights reserved. 38