chapter_9 - In the Dead Sea a lake between Jordan and...

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9
CHAPTER
Solids and Fluids
O U T L I N E
9.1 States of Matter
9.2 The Deformation of Solids
9.3 Density and Pressure
9.4 Variation of Pressure
with Depth
9.5 Pressure Measurements
9.6 Buoyant Forces and
Archimedes’s Principle
9.7 Fluids in Motion
9.8 Other Applications of Fluid
Dynamics
9.9 Surface Tension, Capillary
Action, and Viscous Fluid
Flow
9.10 Transport Phenomena
© Alison Wright/Corbis
There are four known states of matter: solids, liquids, gases, and plasmas. In the universe at
large, plasmas—systems of charged particles interacting electromagnetically—are the most
common. In our environment on Earth, solids, liquids, and gases predominate.
An understanding of the fundamental properties of these different states of matter is im-
portant in all the sciences, in engineering, and in medicine. Forces put stresses on solids, and
stresses can strain, deform, and break those solids, whether they are steel beams or bones.
Fluids under pressure can perform work, or they can carry nutrients and essential solutes, like
the blood flowing through our arteries and veins. Flowing gases cause pressure differences
that can lift a massive cargo plane or the roof off a house in a hurricane. High-temperature
plasmas created in fusion reactors may someday allow humankind to harness the energy
source of the sun.
The study of any one of these states of matter is itself a vast discipline. Here, we’ll intro-
duce basic properties of solids and liquids, the latter including some properties of gases. In
addition, we’ll take a brief look at surface tension, viscosity, osmosis, and diffusion.
9.1 STATES OF MATTER
Matter is normally classified as being in one of three states: solid , liquid , or gas .
Often this classification system is extended to include a fourth state of matter,
called a plasma .
Everyday experience tells us that a solid has a definite volume and shape. A
brick, for example, maintains its familiar shape and size day in and day out. A
In the Dead Sea, a lake between
Jordan and Israel, the high percent-
age of salt dissolved in the water
raises the fluid’s density, dramatically
increasing the buoyant force. Bathers
can kick back and enjoy a good read,
dispensing with the floating lounge
chairs.

9.1 States of Matter
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liquid has a definite volume but no definite shape. When you fill the tank on a
lawn mower, the gasoline changes its shape from that of the original container to
that of the tank on the mower, but the original volume is unchanged. A gas differs
from solids and liquids in that it has neither definite volume nor definite shape.
Because gas can flow, however, it shares many properties with liquids.
All matter consists of some distribution of atoms or molecules. The atoms in a
solid, held together by forces that are mainly electrical, are located at specific posi-
tions with respect to one another and vibrate about those positions. At low temper-
atures, the vibrating motion is slight and the atoms can be considered essentially
fixed. As energy is added to the material, the amplitude of the vibrations increases.