We live in a chemical world that has been partly manufactured through controlled
chemical change. Consider all of the synthetic fibers and plastics that are
used in clothing, housing, and cars. Consider all the synthetic flavors and
additives in foods, how these foods are packaged, and how they are preserved.
Consider also the synthetic drugs and vitamins that keep you healthy. There
are millions of such familiar products that are the direct result of chemical
research. Most of these products simply did not exist sixty years ago. Many of the products of chemical research have remarkably improved the
human condition. For example, synthetic fertilizers have made it possible to
supply food in quantities that would not otherwise be possible. Chemists learned
how to take nitrogen from the air and convert it into fertilizers on an enormous
scale. Other chemical research resulted in products such as weed killers, insecticides,
and mold and fungus inhibitors. The fertilizers and these products have made
it possible to supply food for millions of people who would otherwise have starved
(Figure 12.1). Yet, we also live in a world with concerns about chemical pollutants, the
greenhouse effect, acid rain, and a disappearing ozone shield. The very nitrogen
fertilizers that have increased food supplies also wash into rivers, polluting
the waterways and bays. Such dilemmas require an understanding of chemical products
and the benefits and hazards of possible alternatives. Understanding requires
a knowledge of chemistry, since the benefits, and risks, are chemical in nature. The previous chapters were about the modern atomic theory and how it explains
elements and how compounds are formed in chemical change. This chapter is concerned
with describing chemical changes and the different kinds of chemical reactions
that occur. These reactions are explained with balanced chemical equations,
which are concise descriptions of reactions that produce the products used in
our chemical world. |
2002 McGraw-Hill Higher Education