Back Home Next

A General View of Chemistry
A. Early History and the Scientific Approach
Chemistry as we know it today has its roots in the earliest history of humankind. The ancients were proficient in the arts of metallurgy and dyeing, both of which are chemical in nature. The structure of matter concerned the philosophers of Greece and Rome. The alchemists of the Middle Ages practiced chemistry as they searched for the philosopher's stone that would change "base" matter into gold.

During the eighteenth century, science became a popular hobby of the rich. It was common for men (like Lavoisier) to have laboratories in their homes where they did experiments, considered the implications of the experimental findings, and formulated theories that could be tested by new experiments. These experimentalists met with one another to discuss their work and formulate theories on the nature of matter. This approach to science formed the basis for the pattern of experimentation that was illustrated by Lavoisier's experiment; we call it the scientific method.

According to the scientific method, new knowledge and an understanding of the world around us are most reliably gained if the observers organize their work around the following steps:

The investigators first define the event or situation they wish to explain. The event may be one of which no studies have been made, or it may be one for which our investigators have hypothesized a new explanation.
Careful observations are made about this event. These may be direct observations of nature or observations that others have made.
A hypothesis or model is constructed that explains or consolidates these observations.
New experiments to test the hypothesis are planned and carried out.
The original hypothesis is modified to be consistent with both the new and the original observations and capable of predicting the results of further investigations.

A hypothesis that survives extensive testing becomes accepted as a theory. Although our present hypotheses and theories are the best we have devised thus far, we have no guarantee that they are final. Regardless of how many experiments have been done to test a given theory and how much data has been accumulated to support it, a single experiment that can be repeated by other scientists and whose results contradict the theory forces its modification or rejection. Some of our currently accepted theories on the nature of matter may in the future have to be modified or even rejected on the basis of data from new experiments. We must keep an open mind and be ready to accept new data and new theories.

Definition of problem

Intuititive hypothesis based
on previously collected data

Collection of data specifically aimed at solution
of problem or testing intuitive hypothesis

Tentative statement of hypothesis

Collection of more data to test hypothesis

Restatement of hypothesis

Collection of more data to test restatement of hypothesis

Hypothesis becomes theory,
which continues to be tested using new data

FIGURE 1.6 One possible series of the steps of the scientific
method. Hypothesizing and data collecting continue to alternate
for some time before the hypothesis earns the right to be called a
theory. Although all scientists collect data and form hypotheses,
it is sometimes difficult to describe when each step is taken.

In spite of the vast amounts of new data being collected and the number of new theories being proposed, the understanding of scientific events does not increase at a steady rate. Its forward movement is less like that of a smoothly flowing river than it is like that of a mountain stream, which sometimes rushes ahead and at other times scarcely moves or even wanders off into dead-end swamps. Although there is little doubt that chemical knowledge is expanding, we still have far to go before our understanding of the chemistry of life and of the chemical world in which we live is complete.

An inherent part of the scientific method is the element of creativity. The scientist assembles all of the observations that have been made in a particular area and combines this knowledge in a new way, out of which comes an original and unique hypothesis. For some scientists it is a new concept; for others it is the refinement and clarification of an existing concept. We shall see many examples of creativity in science as we move through this text. Certainly Einstein's equation relating mass and energy is an example of such creativity.

Note the important distinctions between scientific fact and scientific hypothesis and between a scientific law and a scientific theory. A scientific fact is an observed phenomenon, such as the decomposition of sodium hydrogen carbonate on heating. A scientific hypothesis is an attempt to explain a fact, such as an explanation of why heat causes decomposition. A scientific law is the compilation of the observations of many scientific facts, such as the law that all carbonates decompose on heating. A scientific theory scientific theory explains a law. The scientific theory that would accompany the law that all carbonates decompose on heating would explain the relationship between the atoms of a carbonate and how heating changes this relationship so that the carbonate decomposes.

B. The Branches of Modern Chemistry
In recent years chemistry has become a discipline that intrudes on our lives from all directions. There are today hundreds of thousands of practicing chemists. The American chemical Society in 1996 numbered about 145,000 members. Among the many areas of chemistry are the following.

Analytical chemistry. Analytical chemists devise and carryout tests that determine the amount and identity of the pollutants in our air and water. They also devise the tests by which officials determine the unsanctioned use of drugs and steroids by athletes.

Biological chemistry (biochemistry). Biochemists are concerned with the chemistry of living things. They discovered the composition and function of DNA. They are concerned with the chemical basis of disease and the way our bodies utilize food.

Organic chemistry. Organic chemistry once was defined as the chemistry of substances derived from living matter; that definition is no longer valid. We can say only that the substances organic chemists work with usually contain a great deal of carbon and not many metals. Chemists who work with polymers, petroleum, and rubber are organic chemists.

Inorganic chemistry. Originally inorganic chemists were concerned with minerals and ores-substances not derived from living things-but the exact line separating inorganic chemistry from organic chemistry or from biological chemistry has blurred. For example, some inorganic chemists study the behavior of iron (an inorganic substance) in hemoglobin (an organic substance) in blood (clearly the province of a biochemist).

Chemistry is a broad and exciting field that contains numerous other branches, including nuclear chemistry, physical chemistry, and geochemistry, to name three.

Back Home Next