What Chemistry Is
Chemistry is the science of atoms
and molecules the “stuff ” of which everything on Earth and in the universe is
made. At the microscopic level a scale of matter too small to be visible to the
naked eye chemists study the structures of atoms, the shapes of molecules, and
the forces that hold atoms and molecules together. At the macroscopic level a
scale of matter that is visible to the naked eye chemists study the chemical
and physical properties of the states of matter solid, liquid, gas, or mixture.
But chemistry is not only about
matter that is just sitting there. Just as importantly, if not more so,
chemistry is also the science of changes, or transformations, of matter. At a
nuclear level—a scale smaller than an atom itself—these changes may be the transmutation
of one element into another element. At the level of whole atoms and molecules,
these changes involve the processes of breaking chemical bonds and forming new
bonds with the result that one set of chemical substances—or mixtures of
substances—are transformed into a new set of substances that may have
properties that differ completely from those of the original materials.
Finally, chemistry is not limited
only to substances that exist naturally on Earth. Literally millions of new
substances have been synthesized in chemical laboratories that may mimic
substances found in nature, although many times these substances may have
completely novel chemical and physical properties not found in nature.
Chemists are not finished making
new substances. Thousands of new materials are developed every year in
laboratories in countries all over the globe. Some of these new substances may
lead to cures for debilitative diseases. Some substances might lead to more
environmentally sustainable agricultural chemicals or to lightweight, durable
structural materials. Others may result in revolutionary new forms of energy.
Unfortunately, some may also become agents of war and terrorism—agents of
biological and chemical warfare, novel weapon delivery systems, or explosives that
can bypass even the most sophisticated high- technology security systems.
Scientists never know what applications may be found for their discoveries, or
what uses—for good or for evil—others will find for their discoveries.
Chemistry: The Central Science
Chemists often like to call
chemistry the central science because chemistry is fundamental to so many other
endeavors—biology, medicine, agriculture, physics, astronomy, planetary
science, cosmology, geology, and engineering, just to name a few. To say that
chemistry is the science of atoms and molecules is really to say that chemistry
is the science of everything, since all matter is composed of atoms and
molecules.
Examples span all sorts of
substances from raindrops, dew, and mist to puddles, ponds, lakes, and oceans; from sand and gravel to rocks, boulders, and mountains; from
cotton, wool, and silk to nylon, rayon, and polyester; from natural wood
products to plastics, concrete, and steel; from all matter on Earth to all
matter on the Moon and other planets, the Sun and other stars, and even to the
space between stars and galaxies.
It is difficult to think of
anything that is not chemistry. The standard exceptions are usually at the
extremes of the very, very small or the very, very large. On the smallest
scales of matter, chemistry usually stops at the level of the protons,
neutrons, and electrons that make up atoms. It is left to elementary particle
physicists to investigate the properties of matter at smaller scales than
that—the quarks of which protons and neutrons are made, or other subatomic
particles with exotic names like muons, pions, or mesons.
While chemists investigate the
nuclear reactions that take place in stars like our Sun and the chemical
composition of stars and the space between stars, it is astrophysicists and
cosmologists who are concerned about the large scale structures of the
universe—galaxies and clusters of galaxies and how they come into being and
evolve over time.
Chemistry: The Basis of a Global Industry
The millions of chemical
substances—natural or artificial—that have ever been cataloged have had
profound effects on the human race. Cave men and women did not know it, but
their discovery of how to cook foods, especially meat, altered forever the
development of modern humans. Cooking is a chemical reaction that makes food
easier to chew and swallow, more digestible, and freer of harmful pathogens,
all of which contributed to improved human health, increased life spans, and
accelerated brain development.
Substituting metal implements for
stone was chemistry. Cave men and women lived in the Stone Age, when rocks were
either used as they were found or fashioned or sharpened into weapons, tools,
and utensils. The Bronze Age replaced the Stone Age when more modern humans
learned to work with copper. Without knowing it, these people were early
metallurgists, and metallurgy is chemistry. Soon, the Bronze Age was superseded
by the Iron Age, as iron replaced copper in many aspects of life.
In the eighteenth century, the
industrial revolution could not have taken place without chemistry. The
industrial revolution was built on the steam engine, and steam engines required
energy—energy obtained from fuels through chemical processes known as
combustion
Today, the chemical industry is a global
industry with significant investments in many diverse fields:
1. Fossil fuels, from coal and petroleum to natural gas
2. Alternative energy technologies, from nuclear and
solar power to ethanol and hydrogen
3. Pharmaceuticals, everything from analgesics as
ordinary as aspirin to blockbuster drugs that fight heart disease and cancer
4. Cosmetics, from lipstick to perfume
5. Agricultural products, from fertilizers and pesticides
to genetically modified cereal crops
6. Synthetic materials, from plastics and fibers to
rubber
7. Basic chemicals, everything from household cleaners
and wastewater treatment to the pages of this book
So what is chemistry? Everything
is chemistry!
What Chemists Do
Chemistry is what chemists do. The
field of chemistry encompasses a vast range of activities. Because there is so
much demand for the skills of chemists in industry, government, and education,
the American Chemical Society is the largest professional scientific
organization devoted to a single science, with sister organizations in other
countries. Chemists literally are everywhere, and many of them work in
laboratories. Chemists may be researchers, teachers, consultants, sales
representatives, or technicians. Chemists may hold managerial or administrative
positions.
Chemists do all kinds of
interesting work. They may be analyzing moon rocks and meteorites, developing
lifesaving antibiotics, synthesizing new elements, studying the chemistry of
the human body, or probing into theories about the origin of life. Let’s take a
look at some of the subdisciplines
of chemistry in which chemists engage.
Analytical Chemists
From the earliest years of
alchemy, there has been a demand for people who can answer two questions:
·
What is
the composition of a substance?
·
How much
of one substance is present in a mixture of substances?
The first question belongs to the
domain of qualitative analysis, which examines materials to find out what
elements or compounds are in them. The second question belongs to the domain of
quantitative analysis, which measures how much of each element or compound is
present in a mixture of substances.
Qualitative analysis requires that
mixtures be separated into their components, which can be compounds or simple
elements. Compounds, in turn, may be further separated into their constituent
elements. In geology and the mining industry, for example, rocks, minerals, or soils are analyzed to find out what metals (such as copper, nickel,
or titanium) or other elements (such as chlorine or phosphorus) are present.
Municipal water facilities have to
identify and remove any contaminants (such as arsenic, lead, or nitrates) that
might be present in surface or groundwater supplies before the water enters a
city’s water supply system. The food industry analyzes its products so that the
labels can inform consumers of what kinds of fats, proteins, carbohydrates,
vitamins, minerals, and fiber are present in canned, packaged, and prepared
foods. The pharmaceutical industry analyzes samples of all of its products in
the attempt to ensure against contamination.
Historically, quantitative
analysis involved “wet” chemical techniques—titration, filtration, and
gravimetric analysis, for example. Today, most quantitative analyses are done
using
“instrumental” techniques. An example you might be familiar with is the
smog check many municipalities require motor vehicles to pass before they can
be registered. In a smog check, a hose connects the tailpipe of a vehicle to a
machine that can separate the exhaust gases into different categories—carbon
monoxide (CO), oxides of nitrogen (NOx), and unburned hydrocarbons (HC)—and
measure the concentration of each gas in parts per million (ppm).
It makes sense that quantitative
measurements follow qualitative analyses. In the example of rocks and minerals,
once the metal content of ores has been established, then samples of ores can
be assayed to find out what percentage of the ore is a metal of value. In the
food industry example, labels on food products tell not just what is present in
the foods, but how many grams or milligrams of fat, protein, carbohydrates,
vitamins, minerals, and fiber are present per serving.
Organic Chemists
Organic chemistry is all about
carbon and its compounds. The term organic chemistry originated during the
nineteenth century, when chemists thought that carbon-containing substances
could only be made by or in living organisms. That definition is no longer in
use.
Today we simply define an organic
compound as any chemical compound that contains at least carbon and hydrogen.
The reason for including hydrogen is to rule out carbon monoxide (CO) and
carbon dioxide (CO2), both of which contain carbon but are usually classified
as inorganic substances. In addition to carbon and hydrogen, organic compounds
may also contain oxygen, nitrogen, phosphorus, sulfur, and other elements.
Much of the modern chemical
industry is based on organic chemistry. Petroleum, natural gas, lubricating
oils, alcohols, ethers, solvents, weak acids, vitamins and other pharmaceutical
products, and many synthetic polymers are all organic compounds.
Biochemists
Biochemistry is that branch of
organic chemistry that deals with the chemistry of living organisms. Human
bodies, as well as all plants and animals, contain large organic molecules
essential to the many biological processes that define replication of
organisms, growth, and metabolic activities. Important classes of biochemical
substances include carbohydrates, lipids, proteins, and nucleic acids (such as
DNA). Biochemists have contributed to chemical knowledge by elucidating the
pathways by which photosynthesis takes place in green plants and by which
respiration takes place in all living organisms. The syntheses of biologically
important substances such as vitamins, cortisone, and hormones are often done
by biochemists.
Biochemists are often
pharmaceutical chemists. They work for companies that do the research necessary
to develop and bring new drugs to the marketplace. Some of the major advances
that have been made in the battle against disease have been accomplished by
biochemists.
Inorganic Chemists
Simply stated, inorganic chemistry
deals with the 117 elements in the periodic table other than carbon. The
elements in the periodic table are broadly grouped into three classifications:
metals, nonmetals, and metalloids (or semimetals). Inorganic chemists describe
the physical and chemical properties of the elements themselves, as well as all
of the chemical compounds the elements can form, both in nature and in the
laboratory.
Metals—especially iron in the form
of steel—are the workhorses of much of modern heavy industry. Thus, inorganic
chemists work to develop methods for isolating metals from their ores and for
finding new and economically useful applications for metals.
Many nonmetals and their compounds
find essential uses in modern society. Life could not exist without liquid
water. Most living organisms could not exist without oxygen gas.
Chlorine disinfects drinking water
supplies. Salt flavors our food. Neon is used in outdoor lighting. Helium gives
balloons and blimps their buoyancy, although helium’s cryogenic (low
temperature) uses are much more important. Liquid nitrogen is also a cryogenic
substance. In its liquid state carbon dioxide is an environmentally friendly
solvent. Fertilizers are mostly used to supply nitrogen, phosphorus, potassium,
and sulfur to plants in the form of compounds that plants can assimilate.
Hydrogen is being investigated as a clean-burning, renewable fuel that could
substitute for fossil fuels.
The metalloids silicon and
germanium are the building blocks of computer chips and transistors. Many other
elements are used in modern electronics and other technologies. Artificial
radioactive substances are produced and used in hospitals every day both for
medical diagnosis and for medical treatment. In short, unless an element is
particularly rare or expensive, just about every element in the periodic table
finds some use in our society.
Physical Chemists
Physical chemists apply the
methods of physics to an understanding of the variables that affect how
chemical reactions occur so that chemists can control the rates at which
chemical reactions take place and improve the yield of products. Three of the
major subfields of physical chemistry are quantum chemistry, thermodynamics,
and chemical kinetics.
In quantum chemical
studies, chemists relate the structures of atoms and molecules at the most
fundamental microscopic level to the observable properties of elements and
compounds at the macroscopic level. Quantum chemists study the nature of
chemical bonding, the forces that hold molecules together in the solid and
liquid states, and how the shapes of molecules determine the properties of
those substances.
Thermodynamics is the study of chemical equilibrium and of the heat effects associated
with chemical reactions. Very importantly, thermodynamicists are employed to
maximize the yields of synthetic industrial and pharmaceutical chemicals.
Chemical kinetics is the study of the factors that control the rates at which chemical
reactions take place. Kineticists investigate the effects of changing pressure,
concentration of reactants, and temperature on the rates of chemical reactions.
Many reactions take place too slowly for industrial applications at ambient
temperatures and pressures, so kineticists find ways to speed up economically
useful chemical reactions.
One way to speed up chemical
reactions is to employ catalysts, chemical substances that speed up chemical
reactions but that remain unchanged by the reactions. The best catalysts in the
world are biochemical catalysts—the enzymes found in all living organisms. For
many industrial processes, kineticists seek to find catalysts that at least
approach the efficiency of naturally occurring enzymes.
Nuclear Chemists
Another branch of physical
chemistry is nuclear chemistry. Nuclear chemists work with radioactive
materials, which may occur naturally or be produced artificially in nuclear
reactors. Nuclear chemists study the properties of these substances and
investigate ways in which radioactive materials may be useful in a wide range
of applications, including medicine and agriculture among other fields.
For the past three-quarters of a
century, nuclear chemists have synthesized a total of 28 elements that do not
occur in nature but occupy positions in the periodic table after the element
uranium. As of 2012, a total of 118 elements are known. Nuclear chemists
continue to work at extending the periodic table to even heavier elements.
Chemical Engineers
Chemical engineers are applied
physical chemists. Chemical engineers usually work in industry. Their job is to
take benchtop synthetic methods that are usually done on the scale of a few
grams of a substance and scale the processes up to producing metric tons of the
same substances. The ability to apply the principles of thermodynamics and
chemical kinetics to real-life problems of manufacturing useful chemical
substances on a large scale is the trademark of a chemical engineer.
Educational Requirements to be a Chemist
Chemists generally have a college
degree. Community colleges may offer two-year certification programs to be a
laboratory technician. Most four-year colleges and universities offer a
bachelor’s degree in chemistry, and some universities may also offer a
bachelor’s degree in chemical engineering. Colleges and universities with
graduate programs may offer master’s and doctor’s degrees in chemistry.
Entry-level positions in research or sales usually require a bachelor’s or
master’s degree. To be a leader of a research program usually requires a Ph.D.
in chemistry or chemical engineering.
Teaching chemistry at the high
school level usually requires a bachelor’s degree in chemistry, or a degree in
a related science such as biology or physics with a strong chemistry
background. Teaching chemistry at a community college requires a master’s or
doctor’s degree in chemistry. Teaching at a four-year college or university
almost always requires a Ph.D., especially if there is an expectation that
faculty conduct research programs.
Regardless of an undergraduate’s
specific plans for a career in chemistry or other related field, the sequence
of required college courses is fairly standard:
1. One year each of general, organic, and physical
chemistry
2. One semester each of analytical chemistry, advanced
inorganic chemistry, and electives that might include physical organic
chemistry, advanced organic, and inorganic chemistry
3. Biochemistry, or nuclear chemistry
4. One to two years of mathematics, including calculus
and differential equations
5. One year of physics
6. General education courses that include English
composition, speech, computer science, the social sciences, and the humanities
7. Electives that might include additional mathematics or
physics, plus biology, geology, or other areas of interest
Laboratory work is a major
component of an undergraduate education in chemistry. The courses taken during
the first three years usually include laboratory work. In the senior year a
student may take advanced laboratory courses or participate in research under
the supervision of a faculty member. An undergraduate research experience is
especially important for students intending to continue on to graduate
programs. It is not unusual for undergraduate students to have already
published a paper or two in a refereed research journal before graduating.
Here is some advice to remember if
you are a student. You never know where your career path may lead you. A
required course today may be the ticket to success on the job at some future
date. Get the most you can out of every class you take. Get to know your
professors. Believe it or not, they are real people, and you never know when
you might want a letter of recommendation from one of them someday! And don’t
neglect those general education courses. No matter what you do in life, the
ability to communicate—and to communicate well—is essential. Master both oral
and written communication skills, and you will find more doors opening to you
down the road.
Conclusion: Chemistry as a Human Enterprise
Chemistry does not get done all by
itself. People do chemistry. Chemistry, together with all of the other natural
sciences, is as much a human enterprise as are the humanities or the social
sciences. The next chapter is intended to present chemistry within its
historical context, highlighting some of the major figures who have contributed
to chemistry over the centuries.
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