Chapter 14 Liquids and Solids

Chapter 14 Table of Contents Copyright © Cengage Learning. All rights reserved Water and Its Phase Changes 14.2 Energy Requirements for the Changes of State 14.3 Intermolecular Forces 14.4 Evaporation and Vapor Pressure 14.5 The Solid State: Types of Solids 14.6Bonding in Solids

Section 14.1 Water and Its Phase Changes Return to TOC Copyright © Cengage Learning. All rights reserved 3 Reviewing What We Know Gases  Low density  Highly compressible  Fill container Solids  High density  Slightly compressible  Rigid (keeps its shape)

Section 14.1 Water and Its Phase Changes Return to TOC Copyright © Cengage Learning. All rights reserved 4 Heating/Cooling Curve

Section 14.1 Water and Its Phase Changes Return to TOC Copyright © Cengage Learning. All rights reserved 5 Heating/Cooling Curve Normal boiling point: at 1 atm = 100°C Normal freezing point: at 1 atm = 0°C Density  Liquid water = 1.00 g/mL  Ice = g/mL

Section 14.1 Water and Its Phase Changes Return to TOC Copyright © Cengage Learning. All rights reserved 6 Concept Check During the process of melting ice by adding heat, the temperature of the ice/liquid water slurry a)stays constant. b)increases. c)decreases. d)cannot be predicted.

Energy Requirements for the Changes of State Section 14.2 Return to TOC Copyright © Cengage Learning. All rights reserved 7 Changes of state are physical changes.  No chemical bonds are broken.

Energy Requirements for the Changes of State Section 14.2 Return to TOC Copyright © Cengage Learning. All rights reserved 8 Phase Changes When a substance changes from solid to liquid to gas, the molecules remain intact. The changes in state are due to changes in the forces among molecules rather than in those within the molecules.

Energy Requirements for the Changes of State Section 14.2 Return to TOC Copyright © Cengage Learning. All rights reserved 9 Phase Changes Solid to Liquid  As energy is added, the motions of the molecules increase, and they eventually achieve the greater movement and disorder characteristic of a liquid. Liquid to Gas  As more energy is added, the gaseous state is eventually reached, with the individual molecules far apart and interacting relatively little.

Energy Requirements for the Changes of State Section 14.2 Return to TOC Copyright © Cengage Learning. All rights reserved 10 Intramolecular Forces “Within” the molecule. Molecules are formed by sharing electrons between the atoms. Hold the atoms of a molecule together.

Energy Requirements for the Changes of State Section 14.2 Return to TOC Copyright © Cengage Learning. All rights reserved 11 Intermolecular Forces Forces that occur between molecules. Intramolecular bonds are stronger than intermolecular forces.

Energy Requirements for the Changes of State Section 14.2 Return to TOC Copyright © Cengage Learning. All rights reserved 12 Molar heat of fusion – energy required to melt 1 mol of a substance. Molar heat of vaporization – energy required to change 1 mol of a liquid to its vapor.

Energy Requirements for the Changes of State Section 14.2 Return to TOC Copyright © Cengage Learning. All rights reserved 13 Concept Check Which are stronger, intramolecular bonds or intermolecular forces? How do you know?

Energy Requirements for the Changes of State Section 14.2 Return to TOC Copyright © Cengage Learning. All rights reserved 14 Concept Check Which would you predict should be larger for a given substance:  H vap or  H fus ? Explain why.

Energy Requirements for the Changes of State Section 14.2 Return to TOC Copyright © Cengage Learning. All rights reserved 15 Concept Check The unusually high value of the molar heat of vaporization of water (40.6 kJ/mole) is an important factor in moderating the temperature of the earth’s surface, and results in an enormous transfer of energy to the atmosphere as liquid water evaporates as part of the hydrologic cycle. Calculate the amount of heat in kJ needed to evaporate 10.5 kg of liquid water at 100. o C. a)4.27 × 10 5 kJ b)3.15 × 10 4 kJ c)2.37 × 10 4 kJ d)1.18 × 10 3 kJ

Intermolecular Forces Section 14.3 Return to TOC Copyright © Cengage Learning. All rights reserved 16 Forces that occur between molecules.  Dipole–dipole forces  Hydrogen bonding  London dispersion forces

Intermolecular Forces Section 14.3 Return to TOC Copyright © Cengage Learning. All rights reserved 17 Dipole–Dipole Attraction

Intermolecular Forces Section 14.3 Return to TOC Copyright © Cengage Learning. All rights reserved 18 Dipole-Dipole Forces Dipole moment – molecules with polar bonds often behave in an electric field as if they had a center of positive charge and a center of negative charge. Molecules with dipole moments can attract each other electrostatically. They line up so that the positive and negative ends are close to each other. Only about 1% as strong as covalent or ionic bonds.

Intermolecular Forces Section 14.3 Return to TOC Copyright © Cengage Learning. All rights reserved 19 Hydrogen Bonding Strong dipole-dipole forces. Hydrogen is bound to a highly electronegative atom – nitrogen, oxygen, or fluorine.

Intermolecular Forces Section 14.3 Return to TOC Copyright © Cengage Learning. All rights reserved 20 Hydrogen Bonding in Water Blue dotted lines are the intermolecular forces between the water molecules.

Intermolecular Forces Section 14.3 Return to TOC Copyright © Cengage Learning. All rights reserved 21 Hydrogen Bonding Affects physical properties  Boiling point

Intermolecular Forces Section 14.3 Return to TOC Copyright © Cengage Learning. All rights reserved 22 London Dispersion Forces Instantaneous dipole that occurs accidentally in a given atom induces a similar dipole in a neighboring atom. Significant in large atoms/molecules. Occurs in all molecules, including nonpolar ones.

Intermolecular Forces Section 14.3 Return to TOC Copyright © Cengage Learning. All rights reserved 23 London Dispersion Forces – Nonpolar Molecules

Intermolecular Forces Section 14.3 Return to TOC Copyright © Cengage Learning. All rights reserved 24 London Dispersion Forces Become stronger as the sizes of atoms or molecules increase.

Intermolecular Forces Section 14.3 Return to TOC Copyright © Cengage Learning. All rights reserved 25 Melting and Boiling Points In general, the stronger the intermolecular forces, the higher the melting and boiling points.

Intermolecular Forces Section 14.3 Return to TOC Copyright © Cengage Learning. All rights reserved 26 Concept Check Which molecule is capable of forming stronger intermolecular forces? N 2 H 2 O Explain.

Intermolecular Forces Section 14.3 Return to TOC Copyright © Cengage Learning. All rights reserved 27 Concept Check Draw two Lewis structures for the formula C 2 H 6 O and compare the boiling points of the two molecules.

Intermolecular Forces Section 14.3 Return to TOC Copyright © Cengage Learning. All rights reserved 28 Concept Check Which gas would behave more ideally at the same conditions of P and T? CO or N 2 Why?

Intermolecular Forces Section 14.3 Return to TOC Copyright © Cengage Learning. All rights reserved 29 Concept Check Consider the following compounds: NH 3 CH 4 H 2 How many of the compounds above exhibit London dispersion forces? a)0 b)1 c)2 d)3

Section 14.4 Evaporation and Vapor Pressure Return to TOC Copyright © Cengage Learning. All rights reserved 30 Vaporization or Evaporation Molecules of a liquid can escape the liquid’s surface and form a gas. Endothermic process – requires energy to overcome the relatively strong intermolecular forces in the liquid.

Section 14.4 Evaporation and Vapor Pressure Return to TOC Copyright © Cengage Learning. All rights reserved 31 Vapor Pressure Amount of liquid first decreases then becomes constant. Condensation - process by which vapor molecules convert to a liquid. When no further change is visible the opposing processes balance each other – equilibrium

Section 14.4 Evaporation and Vapor Pressure Return to TOC Copyright © Cengage Learning. All rights reserved 32 Vapor Pressure Pressure of the vapor present at equilibrium. The system is at equilibrium when no net change occurs in the amount of liquid or vapor because the two opposite processes exactly balance each other.

Section 14.4 Evaporation and Vapor Pressure Return to TOC Copyright © Cengage Learning. All rights reserved 33 Concept Check What is the vapor pressure of water at 100°C? How do you know? 1 atm

Section 14.4 Evaporation and Vapor Pressure Return to TOC Copyright © Cengage Learning. All rights reserved 34 Vapor Pressure Liquids in which the intermolecular forces are strong have relatively low vapor pressures.

Section 14.4 Evaporation and Vapor Pressure Return to TOC Copyright © Cengage Learning. All rights reserved 35 Concept Check Which of the following would be expected to have the highest vapor pressure at room temperature? a)CH 3 CH 2 CH 2 OH b)CH 3 CH 2 CH 2 NH 2 c)CH 3 CH 2 CH 2 CH 3 d)CH 3 CH 2 CH 3

Section 14.5 The Solid State: Types of Solids Return to TOC Copyright © Cengage Learning. All rights reserved 36 Crystalline Solids Regular arrangement of their components.

Section 14.5 The Solid State: Types of Solids Return to TOC Copyright © Cengage Learning. All rights reserved 37 Types of Crystalline Solids

Section 14.5 The Solid State: Types of Solids Return to TOC Copyright © Cengage Learning. All rights reserved 38 Types of Crystalline Solids Ionic Solids – ions at the points of the lattice that describes the structure of the solid. Molecular Solids – discrete covalently bonded molecules at each of its lattice points. Atomic Solids – atoms at the lattice points that describe the structure of the solid.

Section 14.5 The Solid State: Types of Solids Return to TOC Copyright © Cengage Learning. All rights reserved 39 Examples of Three Types of Crystalline Solids

Section 14.6 Bonding in Solids Return to TOC Copyright © Cengage Learning. All rights reserved 40 Examples of the Various Types of Solids

Section 14.6 Bonding in Solids Return to TOC Copyright © Cengage Learning. All rights reserved 41 Ionic Solids Stable substances with high melting points. Held together by strong forces between ions.

Section 14.6 Bonding in Solids Return to TOC Copyright © Cengage Learning. All rights reserved 42 Molecular Solids Fundamental particle is a molecule. Melt at relatively low temperatures. Held together by weak intermolecular forces.

Section 14.6 Bonding in Solids Return to TOC Copyright © Cengage Learning. All rights reserved 43 Atomic Solids Fundamental particle is the atom. Properties vary greatly.  Group 8 – low melting points  Diamond – very high melting point

Section 14.6 Bonding in Solids Return to TOC Copyright © Cengage Learning. All rights reserved 44 Bonding in Metals Metals are held together by nondirectional covalent bonds (called the electron sea model) among the closely packed atoms.

Section 14.6 Bonding in Solids Return to TOC Copyright © Cengage Learning. All rights reserved 45 Bonding in Metals Metals form alloys of two types.  Substitutional – different atoms are substituted for the host metal atoms.

Section 14.6 Bonding in Solids Return to TOC Copyright © Cengage Learning. All rights reserved 46 Bonding in Metals Metals form alloys of two types.  Interstitial – small atoms are introduced into the “holes” in the metallic structure.

Section 14.6 Bonding in Solids Return to TOC Copyright © Cengage Learning. All rights reserved 47 Copyright © Cengage Learning. All rights reserved 47 Homework Reading assignment –Pages 447 through 467 Homework Problems –Questions and problems 9, 11, 21, 23, 27, 29, 33, 37, 45, 49. Due on Chapter 14 Homework