1.1: What Is Chemistry?

Skills to Develop

1. Define chemistry in relation to other sciences.
2. Identify the general steps in the scientific method.

Chemistry is the study of matter—what it consists of, what its properties are, and how it changes. Being able to describe the ingredients in a cake and how they change when the cake is baked is called chemistry. Matter is anything that has mass and takes up space—that is, anything that is physically real. Some things are easily identified as matter—this book, for example. Others are not so obvious. Because we move so easily through air, we sometimes forget that it, too, is matter.

Chemistry is one branch of science. Science is the process by which we learn about the natural universe by observing, testing, and then generating models that explain our observations. Because the physical universe is so vast, there are many different branches of science (Figure \(\PageIndex{1}\)). Thus, chemistry is the study of matter, biology is the study of living things, and geology is the study of rocks and the earth. Mathematics is the language of science, and we will use it to communicate some of the ideas of chemistry.

Although we divide science into different fields, there is much overlap among them. For example, some biologists and chemists work in both fields so much that their work is called biochemistry. Similarly, geology and chemistry overlap in the field called geochemistry. Figure \(\PageIndex{1}\) shows how many of the individual fields of science are related.

Figure \(\PageIndex{1}\): The Relationships between Some of the Major Branches of Science. Chemistry lies more or less in the middle, which emphasizes its importance to many branches of science.

There are many other fields of science, in addition to the ones (biology, medicine, etc.) listed here.

Looking Closer: Alchemy

As our understanding of the universe has changed over time, so has the practice of science. Chemistry in its modern form, based on principles that we consider valid today, was developed in the 1600s and 1700s. Before that, the study of matter was known as alchemy and was practiced mainly in China, Arabia, Egypt, and Europe.

Alchemy was a somewhat mystical and secretive approach to learning how to manipulate matter. Practitioners, called alchemists, thought that all matter was composed of different proportions of the four basic elements—fire, water, earth, and air—and believed that if you changed the relative proportions of these elements in a substance, you could change the substance. The long-standing attempts to “transmute” common metals into gold represented one goal of alchemy. Alchemy’s other major goal was to synthesize the philosopher’s stone, a material that could impart long life—even immortality. Alchemists used symbols to represent substances, some of which are shown in the accompanying figure. This was not done to better communicate ideas, as chemists do today, but to maintain the secrecy of alchemical knowledge, keeping others from sharing in it.

The first affinity table. Table of different relations observed in chemistry between different substances; Memoirs of the Royal Academy of Sciences, p. 202-212. Alchemists used symbols like these to represent substances.

In spite of this secrecy, in its time alchemy was respected as a serious, scholarly endeavor. Isaac Newton, the great mathematician and physicist, was also an alchemist.

Example \(\PageIndex{1}\)

Which fields of study are branches of science? Explain.

1. sculpture
2. astronomy

SOLUTION

1. Sculpture is not considered a science because it is not a study of some aspect of the natural universe.
2. Astronomy is the study of stars and planets, which are part of the natural universe. Astronomy is therefore a field of science.

How do scientists work? Generally, they follow a process called the scientific method. The scientific method is an organized procedure for learning answers to questions. To find the answer to a question (for example, “Why do birds fly toward Earth’s equator during the cold months?”), a scientist goes through the following steps, which are also illustrated in Figure \(\PageIndex{2}\):

Figure \(\PageIndex{2}\): The General Steps of the Scientific Method

The steps may not be as clear-cut in real life as described here, but most scientific work follows this general outline.

1. Propose a hypothesis. A scientist generates a testable idea, or hypothesis, to try to answer a question or explain how the natural universe works. Some people use the word theory in place of hypothesis, but the word hypothesis is the proper word in science. For scientific applications, the word theory is a general statement that describes a large set of observations and data. A theory represents the highest level of scientific understanding.
2. Test the hypothesis. A scientist evaluates the hypothesis by devising and carrying out experiments to test it. If the hypothesis passes the test, it may be a proper answer to the question. If the hypothesis does not pass the test, it may not be a good answer.
3. Refine the hypothesis if necessary. Depending on the results of experiments, a scientist may want to modify the hypothesis and then test it again. Sometimes the results show the original hypothesis to be completely wrong, in which case a scientist will have to devise a new hypothesis.

Not all scientific investigations are simple enough to be separated into these three discrete steps. But these steps represent the general method by which scientists learn about our natural universe.

In science, we often use words in a slightly different way than in every-day language. In these discussions, it is helpful to understand the scientific meanings. The terms and definitions below were adapted from "Teaching About Evolution and the Nature of Science" by the National Academy of Sciences (Washington, D.C.: National Academy Press, 1998).

TERMS USED IN DESCRIBING THE NATURE OF SCIENCE*

FACT: In science, an observation that has been repeatedly confirmed and for all practical purposes is accepted as "true." Truth in science, however, is never final, and what is accepted as a fact today may be modified or even discarded tomorrow.

(e.g. The statement that water takes up space and has mass is considered a fact.)

HYPOTHESIS: A tentative statement about the natural world leading to deductions that can be tested. If the deductions are verified, it becomes more probable that the hypothesis is correct. If the deductions are incorrect, the original hypothesis can be abandoned or modified. Hypotheses can be used to build more complex inferences and explanations.

(e.g. The hypothesis that everything is made of earth, air, fire, and water has been abandoned by science because experimental tests did not support it.)

LAW: A descriptive generalization about how some aspect of the natural world behaves under stated circumstances.

(e.g. We will study the Law of Conservation of Matter, which states that matter is neither created nor destroyed, but only changes form. So if liquid water evaporates and we can no longer see it, it was not destroyed; it changed to gas that we cannot see.)

THEORY: In science, a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses.

The contention that evolution should be taught as a "theory, not as a fact" confuses the common use of these words with the scientific use. In science, theories do not turn into facts through the accumulation of evidence. Rather, theories are the end points of science. They are understandings that develop from extensive observation, experimentation, and creative reflection. They incorporate a large body of scientific facts, laws, tested hypotheses, and logical inferences.

(e.g. In Chapter 2, you will read about Atomic Theory. It is not a simple observation that we would call a “fact,” nor do we say it is “proven.” It has been supported by so much experimental evidence for such a long time, that it is generally accepted by the scientific community.)

Concept Review Exercises

1. Define science and chemistry.
2. Name the steps of the scientific method.

Answers

1. Science is a process by which we learn about the natural universe by observing, testing, and then generating models that explain our observations. Chemistry is the study of matter.

2. Propose a hypothesis, test the hypothesis, and refine the hypothesis if necessary.

Key Takeaways

• Chemistry is the study of matter and how it behaves.
• The scientific method is the general process by which we learn about the natural universe.