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OVERVIEW

What do you think about when you see a stream (Figure 11.1)? Do you wonder about the water quality and what might
be dissolved in the water? Do you wonder where the stream comes from and if it will ever run out of water?
Many people can look at a stream, but they might think about different things. A farmer might think about how
the water could be diverted and used for crops. A city planner might wonder if the water is safe for domestic use, and
if not, what it would cost to treat the water. Others might wonder if the stream has large fish they could catch. Many
large streams can provide water for crops, domestic use, and recreation and still meet the requirements for a number
of other uses.
It is the specific properties of water that make it important for agriculture, domestic use, and recreation. Living
things evolved in a watery environment, so water and its properties are essential to life on Earth. Some properties of
water, such as the ability to dissolve almost anything, also make water very easy to pollute. This chapter is concerned
with some of the unique properties of water, water solutions, and the household use of water.

water by not letting the water run continuously while brushing
11.1 HOUSEHOLD WATER your teeth.

Water is an essential resource, not only because it is required It is often difficult to convince people to conserve water
for life processes but also because of its role in a modern when it is viewed as an inexpensive, limitless resource. How-
society. Water is used in the home for drinking and cooking ever, efforts to conserve water increase dramatically as the cost
(2 percent), cleaning dishes (6 percent), laundry (11 percent), to the household consumer increases.
bathing (23 percent), toilets (29 percent), and maintaining The issues involved in maintaining a safe water supply
lawns and gardens (29 percent). are better understood by considering some of the proper-
The water supply is obtained from streams, lakes, and ties of water and water solutions. These are the topics of the
reservoirs on the surface or from groundwater pumped from following sections.
below the surface. Surface water contains more sediments, bac-
teria, and possible pollutants than water from a well because it
is exposed to the atmosphere and water runs off the land into 11.2 PROPERTIES OF WATER
streams and rivers. Surface water requires filtering to remove
suspended particles, treatment to kill bacteria, and sometimes Water is essential for life since living organisms are made up of
processing to remove pollution. Well water is generally cleaner cells filled with water and a great variety of dissolved substances.
but still might require treatment to kill bacteria and remove pol- Foods are mostly water, with fruits and vegetables containing
lution that has seeped through the ground from waste dumps, up to 95 percent water and meat consisting of about 50 percent
agricultural activities, or industrial sites. water. Your body is over 70 percent water by weight. Since water
Most pollutants are usually too dilute to be considered a is such a large component of living things, understanding the
significant health hazard, but there are exceptions. There are properties of water is important to understanding life. One im-
five types of contamination found in U.S. drinking water that portant property is water’s unusual ability to act as a solvent.
are responsible for the most widespread danger, and these are Water is called a universal solvent because of its ability to dis-
listed in Table 11.1. In spite of these general concerns and other solve most molecules. In living things, these dissolved mole-
occasional local problems, the U.S. water supply is considered to cules can be transported from one place to another by diffusion
be among the cleanest in the world. or by some kind of a circulatory system.
The demand for domestic water sometimes exceeds the The usefulness of water does not end with its unique abil-
immediate supply in some metropolitan areas. This is most ities as a solvent and transporter; it has many more properties
common during the summer, when water demand is high and that are useful, although unusual. For example, unlike other
rainfall is often low. Communities in these areas often have pub- liquids, water in its liquid phase has a greater density than
lic education campaigns designed to help reduce the demand solid water (ice). This important property enables solid ice to
for water. For example, did you know that taking a tub bath can float on the surface of liquid water, insulating the water below
use up to 135 liters (about 36 gal) of water compared to only and permitting fish and other water organisms to survive the
95 liters (about 25 gal) for a regular shower? Even more water winter. If ice were denser than water, it would sink, freezing
is saved by a shower that does not run continuously—wetting all lakes and rivers from the bottom up. Fish and most organ-
down, soaping up, and rinsing off uses only 15 liters (about isms that live in water would not be able to survive in a lake
4 gal) of water. You can also save about 35 liters (about 9 gal) of or river of solid ice.

276 CHAPTER 11 Water and Solutions 11-2