Chapter 11: States of Matter and Intermolecular Forces
Intermolecular forces determine whether a substance will be solid, liquid, or gas. The vapor pressure of a liquid and the heat
of vaporization are good measures of these intermolecular forces. Phase changes of solids are discussed next, followed by
summarizing these phase changes into a phase diagram. Then each type of intermolecular force is discussed: dispersion
forces, dipole-dipole forces, and hydrogen bonds. These then are applied in the discussion of surface tension and viscosity.
The chapter ends with a discussion of solids: network covalent solids and ionic solids, and different crystal structures.
Summary of Sections
Intermolecular Forces and the States of Matter: A Chapter Preview
This introduction to the chapter establishes that intermolecular forces exist and create the condensed states of matter. It also
introduces the concept of a phase diagram and states the conditions under which each phase is stable. In many ways, this
chapter brings together much of what has come before. The kinetic molecular theory's explanation of the behavior of gases
helps one understand how liquids and solids behave. An understanding of how heat is transferred is needed to explain phase
changes. Shapes of molecules enable one to predict which molecules will exert which kinds of intermolecular forces.
Describe intermolecular forces.
Vaporization and Vapor Pressure
This section describes and explains vaporization, heat of vaporization, condensation, vapor pressure, boiling point, normal
boiling point, and critical point.
The relative strengths of forces between molecules are the reasons why these properties
have different values for different substances.
Define vaporization and the enthalpy of vaporization. Define vapor pressure and know the relationship between
vapor pressure and boiling point.
Phase Changes Involving Solids
This section describes and explains melting, freezing, heat of fusion, relative invariance of melting point with pressure,
sublimation, heat of sublimation, variation of sublimation pressure with temperature, sublimation as the sum of fusion and
vaporization, and the triple point.
Describe phase changes between a liquid and a solid. Define sublimation and relate the enthalpy of sublimation
to the enthalpy of fusion and the enthalpy of vaporization.
Define critical point, critical temperature, and critical pressure. Define the state of a substance from a phase
diagram and determine the triple point.
Intermolecular Forces of the van der Waals Type
Both dispersion forces and dipole-dipole forces influence the behavior of molecules. The factors that produce strong
dispersion forces are many electrons, few nuclei, and elongated molecules - these make molecules polarizable.