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1.1: What is Chemistry?

Difficulty Level: At Grade Created by: CK-12
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Lesson Objectives

  • Define chemistry.
  • Differentiate between the macroscopic and the microscopic as it relates to chemistry.
  • Know the relationship between pure chemistry and applied chemistry.
  • Identify and describe the five primary disciplines of chemistry.
  • Describe some of the concerns of the modern world in which chemistry has played and will continue to play a role.

Lesson Vocabulary

  • analytical chemistry
  • applied chemistry
  • biochemistry
  • chemistry
  • inorganic chemistry
  • macroscopic
  • matter
  • microscopic
  • organic chemistry
  • physical chemistry
  • pure chemistry

Check Your Understanding

Recalling Prior Knowledge

  • What are some areas of science with which you are familiar?
  • List some of the chemicals that influence your everyday life.

Chemistry is a diverse and fascinating science that impacts our lives each and every day. In this first lesson, you will learn what chemistry is and some of the ways in which chemistry influences the modern world.

A Definition of Chemistry

Science is a general term used to describe the principled, rigorous study of the natural world. Many interconnected disciplines fall under this broader concept. For example, physics is the study of motion and forces. Biology is the study of living things. Geology is the study of the Earth and the rocks and minerals of which it is comprised. In this text, you will learn about the field of chemistry. Chemistry is the study of the composition of matter and the changes that matter undergoes. Matter is anything that has mass and takes up space. Virtually everything around us is matter, including both living and nonliving things. Chemistry affects nearly everything we see and every action we take. Chemistry explains why the leaves of deciduous trees turn from green in the summer to various shades of red and yellow in the autumn (Figure below). Chemistry explains why milk that is left in the refrigerator for too long turns sour. Chemistry explains why certain pollutants called chlorofluorocarbons have done lasting damage to the ozone layer of our planet. Chemistry is very much a central, foundational science, and a basic knowledge of chemistry is essential for students who are pursuing studies in biology, geology, environmental science, medicine, and many other subjects.

Chemical reactions in the leaves of deciduous trees cause them to change color from green to red, orange, or yellow before dropping to the ground.

Chemists are tasked with looking at the world in two ways, often simultaneously. The two worlds of the chemist are the macroscopic world and the microscopic world. Macroscopic refers to substances and objects that can be seen, touched, and measured directly. Microscopic refers to the small particles that make up all matter. Chemists must observe matter and do experiments in the macroscopic world and then use their observations to make generalizations and propose explanations that are microscopic in nature. For example, anyone can observe the physical change in appearance that occurs as an iron object rusts, such as a tractor that is left outside for a long enough period of time. However, a chemist looks at the rusting tractor and thinks about what is going on with the individual atoms that make up the iron and how they are changing as a result of exposure to rainwater or oxygen in the air. Throughout your study of chemistry, you will often need to switch back and forth between the macroscopic and microscopic worlds.


Chemistry is a subject that has its roots in the ancient tradition known as alchemy, from which it derives its name. Alchemy was a combination of philosophy and science that had both practical and mystical aspects. The goals of alchemy were varied and difficult to summarize. In many ways, the alchemists sought to achieve perfection, through such actions as the pursuit of the philosopher’s stone and the elixir of life (Figure below). The philosopher’s stone, it was believed, was a substance that was capable of being used to turn base metals (such as lead) into gold. It was also believed that it could be used to achieve rejuvenation and perhaps immortality. While alchemists did not ultimately succeed in these quests, their work provided the foundation for the modern study of chemistry.

Alchemists laid the groundwork for many chemical processes, such as the refining of ores, the production of gunpowder, the manufacture of glass and ceramics, leather tanning, and the production of inks, dyes, and paints. Alchemists also made the first attempts at organizing and classifying substances so that they could better understand their reactions and be able to predict the products of their experiments. This eventually led to the modern periodic table, which you will learn about in a later chapter. Alchemy began to fully evolve into chemistry in the 17th century, with a greater emphasis on rational thought and experimentation and less emphasis on spirituality and mysticism.

This painting by Joseph Wright (1771) is titled “The Alchymist, In Search of the Philosopher’s Stone.”

Pure and Applied Chemistry

The study of modern chemistry can be split into two categories, called pure chemistry and applied chemistry. Chemists who study pure chemistry do research primarily to advance mankind's understanding of chemistry. Pure chemistry is concerned with a greater understanding of the theories behind how matter is changing in chemical reactions. Pure chemists tend to be less concerned with direct applications of the research that they are doing. That is not to say that pure chemistry can never lead to a real-world application, but rather that a potential application is not the primary motivation for doing the research in the first place. Applied chemistry is chemistry that is directed towards a specific practical goal or application.

The line between pure chemistry and applied chemistry is not always distinct. For example, in the early 1960s, chemists at DuPont were searching for a new lightweight and strong fiber that could be used in tires. Chemist Stephanie Kwolek discovered, somewhat by accident, that a certain solution she had made displayed unique characteristics that were unlike those of other previously developed substances. The field of polymer chemistry arose in part out of her research. Polymers are very, very large molecules comprised of smaller subunits that are repeated over and over again in extremely long chains. The polymer that was discovered at DuPont was eventually given the name Kevlar. It is used not only in tires but also in bulletproof body armor because of its high strength and light weight. Polymer chemistry continues to be an active and vibrant field of chemistry, as both a pure and an applied discipline.

Chemistry Disciplines

The study of modern chemistry has many, many branches, but it can generally be broken down into five main disciplines, or areas of study. Physical chemistry is the study of both macroscopic and atomic properties and phenomena in chemical systems. A physical chemist may study such things as the rates of chemical reactions, the energy transfers that occur during a reaction, or the physical structure of materials at the molecular level. Organic chemistry is the study of carbon-containing chemicals. Carbon is one of the most abundant elements on Earth and is capable of forming a tremendously vast number of chemicals. Most of the chemicals found in living organisms are based on carbon. Inorganic chemistry is the study of chemicals that do not, in general, contain carbon. Inorganic chemicals are commonly found in rocks and minerals. Analytical chemistry is the study of the composition of matter, with a focus on separating, identifying, and quantifying chemical samples. An analytical chemist may use complex instruments to analyze an unknown material in order to determine its various components (Figure below). Biochemistry is the study of chemical processes that occur in living things. Due to the importance of carbon-containing compounds in living organisms, biochemistry and organic chemistry are often closely interrelated.

Nuclear magnetic resonance (NMR) is an analytical technique that uses very large magnets in order to learn about the specific makeup of complex chemicals. Pictured is a 900 MHz NMR spectrometer located in Washington, USA.

In practice, chemical research is often not limited to just one of the five major disciplines. For example, a chemist might use biochemistry techniques to isolate a particular chemical from the human body, such as hemoglobin, the oxygen-carrying component of red blood cells. He or she may then proceed to analyze the hemoglobin using methods that would pertain to physical or analytical chemistry. Many chemists specialize in areas that are combinations of these primary disciplines, such as bioinorganic chemistry or physical organic chemistry.

Chemistry in the World Today

Chemistry has played and will continue to play a central role in all areas of science and technology. Before delving into the specifics of chemistry, it is worthwhile to examine a few of the frontiers that chemists are currently exploring and to review how chemistry has helped shape these fields.


Virtually all chemical reactions involve a transfer of energy, and the worldwide demand for energy continues to increase every year. The majority of our energy needs since the Industrial Revolution have been met by the burning of fossil fuels. Fossil fuels (coal, petroleum, natural gas) were formed millions of years ago from the remains of plants and animals. Fossil fuels are a nonrenewable energy source, meaning that they cannot be produced or regenerated, so the global supply will eventually be exhausted. Chemists are actively involved in finding ways to conserve energy and to utilize alternative energy sources.

Nuclear energy is obtained by splitting large atoms such as uranium into smaller atoms in a process called nuclear fission. Nuclear fission releases tremendous amounts of energy, much more than burning an equivalent amount of fossil fuels. While nuclear energy is widely used to supplement the energy demands of modern society, it comes with risks and drawbacks. For example, nuclear power generates waste that is dangerously radioactive and difficult to store safely. Chemists are currently searching for better ways to store nuclear waste. Nuclear fusion, the process that occurs in the Sun and other stars, is an alternative that does not generate the same type of waste as nuclear fission. Scientists are actively trying to make nuclear fusion a practical source of energy.

Biofuels are an alternative energy source that has gained a great deal of attention in recent years (Figure below). Various types of biofuels are obtained from vegetable oils, animal fats, and the decomposition of corn or other crops. Although the use of biofuels lessens our dependence on fossil fuels, it still involves the burning of carbon-based chemicals, which contributes to climate change.

This city bus is powered by biofuel derived from soybean oil.

Finding alternative energy sources that are renewable and do not harm the environment is a primary goal for scientists working in this field. Renewable energy sources are those that either will not run out or that can be used over and over again. Chemists and other scientists are actively involved in the search for these energy sources and for ways to make their use widespread and practical. Solar energy involves the direct transformation of the energy from the Sun into electricity by the use of devices called photovoltaic cells. Energy from wind can be obtained from the use of giant windmills. Wind power is an energy source that has been on the rise in recent years, with an increasing number of “wind farms” being built both on land and offshore. Geothermal energy is energy that is generated and stored deep within the Earth. This energy source can also be tapped and used to generate electricity.


Advances in medicine over the last century have dramatically increased lifespans and improved our quality of life. Chemists are at the forefront of many of these medical breakthroughs and improvements. Medical researchers work with doctors to gain a better understanding of biological processes that occur in the human body. Today, thousands of prescription and over-the-counter drugs are available to treat everything from a simple headache to major infections, high blood pressure, depression, and a host of other ailments. Drugs work because of their interactions with other chemicals in the body. Chemists are constantly working to improve existing drugs, to design new and better drugs, and to further their understanding of the chemical mechanisms by which drugs perform their functions.

Chemists are also involved in designing materials that are used to repair or replace body parts. Artificial hips and knees can be inserted into a person’s body so that he or she can walk without pain (Figure below). Burn victims benefit from replacement skin. Diseased arteries can be replaced with plastic tubing that must be able to withstand the harsh environment found inside a human body without degrading or malfunctioning.

A prosthetic hip made of titanium, with a ceramic head and a polyethylene cup

Biotechnology is an emerging field that involves the manipulation of DNA, the chemicals that store the genetic information that gets passed on from one generation to the next. Genes are the pieces of DNA that contain this genetic information. Biochemists can transfer genes from one organism to another in order to take advantage of useful traits. For example, genes from a certain bacteria produce a chemical that confers resistance to certain crop-eating pests. Inserting these genes into the genetic material of corn plants results in genetically modified corn that is able to resist the pest without having to be sprayed with a chemical pesticide. Bacteria can also be used as “chemical factories” to produce useful drugs such as insulin, which is used to treat some forms of diabetes.


Chemists are also involved in the design and production of new materials. Some of the materials that chemists have helped discover or develop in recent years include polymers, ceramics, adhesives, coatings, and liquid crystals. Liquid crystals are used in electronic displays, such as those found in watches and calculators. Silicon-based computer chips have revolutionized modern society, and chemists have played a key role in their design and continued development. Many chemists are currently working in the field of superconductivity. Superconductors are materials that can conduct electricity with 100% efficiency. Unlike conventional conducting materials, like copper cables, no energy is lost during electrical transmission through superconductors. Unfortunately, most known superconductors only exhibit this property at extremely low temperatures. A current challenge in this field is to design materials that can act as superconductors at normal temperatures.

The Environment

There is a great deal of concern about the deleterious effects that humankind has had and continues to have on the natural environment. The burning of fossil fuels pumps millions of tons of carbon dioxide into the atmosphere. Carbon dioxide is a greenhouse gas, which means that it traps the heat from the Sun and prevents it from being released back out into space in the form of infrared radiation. As a result, the temperature of the Earth is slowly climbing. Chemists, along with environmental scientists, are searching for ways to slow or reverse the effects of global warming. One way, as mentioned previously, is to develop alternative energy sources such as wind power that do not emit carbon dioxide.

Many other chemicals that were once commonly used were later found to be harmful to the environment, to human health, or both. The element lead was once a common additive to gasoline and to paint. Plumbing pipes were once typically made of lead. Only since the 1970s has the danger of lead become apparent. Too much exposure to lead can cause brain damage, and small children (who often chewed on objects painted with lead-based paint) are particularly susceptible to this effect. The use of lead in gasoline, paint, and plumbing pipes is now banned. Mercury is another toxic element whose use was once far more widespread than it is today, especially in many industrial processes. Chemists continue to look for threats to our health and the environment and to search for substitutes so that harmful chemicals can be replaced with equally effective but less harmful alternatives.


The world’s population has increased dramatically over the last century. It is becoming challenging to feed this population, since the amount of land available to grow food is limited. Even worse, the amount of usable land is declining as some of it is being converted to living areas. Chemists are involved in efforts to make the land that is used for agriculture as efficient and productive as possible. Some factors that decrease productivity include poor soil quality, lack of sufficient water, crop-eating pests, weeds, and diseases. Chemists are involved in the study of soils, including how to improve existing soils and to develop techniques so that soils do not lose their nutrients. Fertilizers are used to provide crop plants with vital nutrients, but the excessive use of fertilizers is harmful to the environment, particularly when the fertilizer runs off the land and into the water supply (Figure below). Herbicides and insecticides have traditionally been applied to crops in order to reduce losses from weeds and insects. However, pesticides contain toxic chemicals that are potentially harmful to other organisms, including humans. Chemists are involved in developing alternatives to traditional pesticides so that the use of these harmful chemicals can be reduced. Biotechnology was mentioned previously as a way to increase the resistance of crops to pests. Pests can also be attacked by using natural chemicals to disrupt their mating and reproductive mechanisms so that the overall number of pests declines.

Runoff from excessive fertilizer usage can cause an algal bloom due to the large increase in nutrient levels that causes algae populations to explode. Algal blooms are harmful to the natural processes of the aquatic ecosystem.

Lesson Summary

  • Chemistry is the study of matter and its changes. Chemistry is closely interrelated with other scientific fields, such as biology and geology.
  • Chemists examine and explain their observations on both macroscopic and microscopic levels.
  • Pure chemistry is devoted to the acquisition of chemical knowledge, while applied chemistry is focused on a specific goal.
  • The five main disciplines of chemistry are physical, organic, inorganic, analytical, and biochemistry.
  • Chemistry has modern applications in the fields of energy, medicine, materials science, the environment, and agriculture.

Lesson Review Questions

Reviewing Concepts

  1. Which of the following scientific inquiries involve chemistry? For the others, what field of science is being described?
    1. how long it takes for an object to fall from a rooftop to the ground
    2. how fast a flammable liquid burns
    3. the amount of pollutants in a lake
    4. the structure of a plant cell
  2. The same event is described in two ways below. Which description focuses on the macroscopic level and which focuses on the microscopic level?
    1. Chemical bonds between oxygen atoms and hydrogen atoms are broken.
    2. When an electric current passes through water, a gas is produced.
  3. State whether each of the chemists below is practicing pure chemistry or applied chemistry. Explain.
    1. He is attempting to formulate a new adhesive that works well in extremely cold temperatures.
    2. She is studying reactions of the element sodium with different gases.
  4. Which of the five main chemistry disciplines is most closely related to each of the actions described below?
    1. Studying the digestion of certain types of foods
    2. Investigating the iron content of different samples of ore
    3. Measuring how much energy is released in a series of reactions
    4. Attempting to produce a new carbon-based chemical
    5. Measuring the amount of mercury contamination in a sample of river water
  5. What is the difference between renewable and nonrenewable energy?
  6. Identify the following energy sources as renewable or nonrenewable.
    1. fossil fuels
    2. solar energy
    3. nuclear power
    4. wind
    5. geothermal energy
  7. Name a process that is involved in biotechnology.
  8. What are greenhouse gases and why is their production considered to be an environmental problem?
  9. What are two alternatives to the traditional use of chemically-based pesticides in agriculture?

Further Reading / Supplemental Links

Points to Consider

Chemists, like all scientists, rely on a rigorous and systematic approach to studying the world called the scientific method.

  • What are the steps of the scientific method?
  • How do chemists and other scientists communicate their findings to the public?

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