Section 14.1 Intermolecular Forces and Phase Changes Steven S. Zumdahl Susan A. Zumdahl Donald J. DeCoste Gretchen M. Adams University of Illinois at Urbana-Champaign Chapter 14 Liquids and Solids

Section 14.1 Intermolecular Forces and Phase Changes 1. To learn about dipole-dipole, hydrogen bonding and London dispersion forces 2. To understand the effect of intermolecular forces on the properties of liquids 3. To learn some of the important features of water 4. To learn about interactions among water molecules 5. To understand and use heat of fusion and heat of vaporization Objectives: Learning Target 1, 2, 4, 5

Section 14.1 Intermolecular Forces and Phase Changes A. Intermolecular Forces Low density Highly compressible Fill container Reviewing what we know GasesSolids High density Slightly compressible Rigid (keeps its shape)

Section 14.1 Intermolecular Forces and Phase Changes A. Intermolecular Forces Intermolecular forces – occur between molecules Intramolecular forces – occur inside the molecules

Section 14.1 Intermolecular Forces and Phase Changes Concept Check Which are stronger, intramolecular bonds or intermolecular forces? How do you know?

Section 14.1 Intermolecular Forces and Phase Changes A. Intermolecular Forces Dipole – dipole attraction

Section 14.1 Intermolecular Forces and Phase Changes A. Intermolecular Forces Occurs between H and highly electronegative atom (for example N, O, F) Hydrogen Bonding

Section 14.1 Intermolecular Forces and Phase Changes A. Intermolecular Forces Affects physical properties  Boiling point Hydrogen Bonding

Section 14.1 Intermolecular Forces and Phase Changes A. Intermolecular Forces Formation of instantaneous dipoles London Dispersion Forces

Section 14.1 Intermolecular Forces and Phase Changes A. Intermolecular Forces Nonpolar molecules London Dispersion Forces

Section 14.1 Intermolecular Forces and Phase Changes A. Intermolecular Forces Become stronger as the sizes of atoms or molecules increase London Dispersion Forces

Section 14.1 Intermolecular Forces and Phase Changes Concept Check Which molecule is capable of forming stronger intermolecular forces? N 2 H 2 O Explain.

Section 14.1 Intermolecular Forces and Phase Changes Concept Check Compare the two Lewis structures for the formula C 2 H 6 O and compare the boiling points of the two molecules.

Section 14.1 Intermolecular Forces and Phase Changes Concept Check Which gas would behave more ideally at the same conditions of P and T? CO or N 2 Why?

Section 14.1 Intermolecular Forces and Phase Changes B. Water and Its Phase Changes Heating/cooling curve

Section 14.1 Intermolecular Forces and Phase Changes B. Water and Its Phase Changes Normal boiling point – at 1 atm = 100 o C Normal freezing point – at 1 atm = 0 o C Density  Liquid water = 1.00 g/mL  Ice = g/mL

Section 14.1 Intermolecular Forces and Phase Changes Concept Check Which would you predict should be larger for a given substance:  H vap or  H fus ? Explain why.

Section 14.1 Intermolecular Forces and Phase Changes C. Energy Requirements for the Changes of State Changes of state are physical changes.  No chemical bonds are broken.

Section 14.1 Intermolecular Forces and Phase Changes C. Energy Requirements for the Changes of State 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

Section 14.2 Vapor Pressure and Boiling Point 1.To understand the relationship among vaporization, condensation and vapor pressure 2.To relate the boiling point of water to its vapor pressure Objectives: Learning Target 6

Section 14.2 Vapor Pressure and Boiling Point A. Evaporation and Vapor Pressure Vaporization or evaporation  Endothermic

Section 14.2 Vapor Pressure and Boiling Point A. Evaporation and 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 Vapor Pressure

Section 14.2 Vapor Pressure and Boiling Point A. Evaporation and Vapor Pressure Vapor pressure - pressure of the vapor present at equilibrium with its liquid Vapor Pressure  Vapor pressures vary widely - relates to intermolecular forces

Section 14.2 Vapor Pressure and Boiling Point B. Boiling Point and Vapor Pressure

Section 14.2 Vapor Pressure and Boiling Point B. Boiling Point and Vapor Pressure

Section 14.2 Vapor Pressure and Boiling Point Concept Check What is the vapor pressure of water at 100°C? How do you know? 1 atm

Section 14.3 Properties of Solids Concept Check As intermolecular forces increase, what happens to each of the following? Why?  Boiling point  Surface tension  Enthalpy of fusion  Freezing point  Vapor pressure  Heat of vaporization

Section 14.3 Properties of Solids 1.To learn about the types of crystalline solids 2.To understand the interparticle forces in crystalline solids 3.To learn how the bonding in metals determines metallic properties Objectives: Learning Target 3

Section 14.3 Properties of Solids A. The Solid State: Types of Solids Crystalline solids

Section 14.3 Properties of Solids A. The Solid State: Types of Solids

Section 14.3 Properties of Solids A. The Solid State: Types of Solids

Section 14.3 Properties of Solids B. Bonding in Solids

Section 14.3 Properties of Solids B. Bonding in Solids Stable substances with high melting points Held together by strong forces between ions Ionic Solids

Section 14.3 Properties of Solids B. Bonding in Solids Fundamental particle is a molecule Melt at relatively low temperatures Held together by weak intermolecular forces Molecular Solids

Section 14.3 Properties of Solids B. Bonding in Solids Fundamental particle is the atom Properties vary greatly  Group 8 - low melting points  Diamond - very high melting point Atomic Solids

Section 14.3 Properties of Solids B. Bonding in Solids Metals are held together by nondirectional covalent bonds (called the electron sea model) among the closely packed atoms. Bonding in Metals

Section 14.3 Properties of Solids B. Bonding in Solids Metals form alloys of two types. Bonding in Metals  Substitutional – different atoms are substituted for the host metal atoms

Section 14.3 Properties of Solids B. Bonding in Solids Metals form alloys of two types. Bonding in Metals  Interstitial – small atoms are introduced into the “holes” in the metallic structure