Chapter 7 States of Matter and Changes in State
7.0 Introduction7.5 Liquids7.1 Gases7.6 Changes in State7.2 Kinetic Molecular Theory and Thermal Energy7.7 Chapter Summary and Objectives7.3 Intermolecular Forces7.8 Exercises7.4 Solids7.0
INTRODUCTION
The substances we deal with every day exist in one of three states of matter: solid, liquid or gas. The molecules in the liquid and solid st
ates are much closer to one another than are
the molecules in the gas st
ate, so the solid and liquid states are often called the
condensed
states
. Substances are held in the condensed
states by Coulombic forces between the
molecules. Indeed, it is the strength of these forc
es that dictates the state of matter adopted
by a substance at a given temperature and pressure.
We experience some substances in all three states: water is commonly found as solid
ice, liquid water, and steam. However, manyother substances are us
ually observed in only
one state: copper, iron, sugar, and salt are
found as solids; mercury as only a liquid; and
oxygen, nitrogen, and helium as gases. Substances are seldom found as pure liquids because there is always some vapor above th
e liquid. Indeed, the odor associated with a
liquid is due to vapor molecules that have escaped from the liquid. In this chapter, we examine the behavior of gases and the forces th
at are responsible for the condensed states.
We then briefly discuss the liquid state, defi
ne the solid state, and conclude with a
discussion of changes in state. THE OBJECTIVES OF CHAPTER 7 ARE TO: •
characterize the different states of matter;(^) •
describe the behavior of gases;
(^) •
explain the postulates of kinetic-molecular theory;
(^) •
define the absolute temperature scale;
(^) •
discuss the meaning of the term
thermal energy
;
(^) •
apply some of the general concepts of kinetic-molecular theory to phase equilibria;
(^) •
explain the origin of intermolecular forces;
Chapter 7 States of Matter and Changes in State
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