Chemistry, at its most basic, is the branch of science which studies the nature of, and changes in, physical matter – that is, chemicals. Whereas physics studies the composition of matter from the perspective of movement and energy, chemistry does so from the perspective of analyzing how matter is structured – through atoms and molecules – as well as how those structures undergo change through chemical processes called reactions. The majority of chemists are currently involved in the study of the so-called organic compounds – molecules based on the complex bonding capabilities of carbon atoms. In the past, however, most interest lay in inorganic compounds, common examples of which include water and table salt.
Fred Senese of Frostburg State University identifies five basic components which must go into a definition of chemistry: chemistry is (1) a branch of science; (2) as a science, it is a “systematic study” of natural phenomena, using the scientific method and rigorous testing protocols to build viable theories; (3) it is the study of “the composition and properties of matter”; (4) specifically, it studies chemical reactions within that matter; and (5) it is divided into organic and inorganic chemistry.
– Messy Definitions –
Of course, as John Russellof the University of Cork (in Ireland) points out, to the non-chemist such a definition can easily raise more questions than it answers. It was, he notes, deceptively simple to define chemistry as the study of matter a century ago, when physicists, chemists and geologists studied the natural world; biologists, zoologists and botanists studied the world of life; and anthropologists studied the social world (in other words, the classical division between physical science, life science, and social science). Now, however, the fields are much more overlapping. There are, for example, peer-reviewed journals and graduate programs in neurochemistry – essentially psychology, except studied from the perspective of chemists’ analyses of the chemical makeup of the brain.
This, however, is essentially just a jurisdictional problem: one of the endless disputes among Ivory Tower academics about the nature of interdisciplinary studies. More problematic to the layperson is the simple question of what it means to say that chemists study changes in matter. Ironically, this also increasingly became a problem for theoretical scientists during the twentieth century, as it became clear that matter was simply a particular form of concentrated energy.
Instead of muddling further through the details of Russell’s and Senese’s work, it might now be best to turn to the two most basic parts of an easy definition of chemistry.
– 1. Chemistry Studies Matter –
Matter, put most simply (and leaving aside the theoretical physicists’ objections noted above), simply refers to physical substances, which we encounter in everyday life: the gases which make up the atmosphere; liquids, like water; and solids, like the ground beneath our feet. Chemistry studies all of these things, but it does so on an extremely tiny scale, seeking to understand and manipulate the atoms and molecules which make up these solids, liquids, and gases.
In general, chemists have been concerned with two things about matter at the atomic level. First, they have sought to understand how that matter is made up. Protons, neutrons, and electrons combine in particular ways to form atoms. These atoms will be of different types – chemicals, specifically called “elements,” such as oxygen and helium – based on how many protons are found within them.
Second, chemists have sought to understand how that matter interacts. A large proportion of the chemicals we encounter in everyday life are not actually atoms, or elements in their most basic form. Instead, they are compounds, or molecules: atoms which have combined together to form chains with different physical properties than the elemental atoms which go into creating them. Water, for example, is a compound created by two hydrogen atoms and one oxygen atom; table salt is another compound, created by bonding one sodium atom with one chlorine atom.
– 2. Chemistry is Science –
The particular approach that chemists take to understanding matter, and changes in matter, is known as the scientific method. Like other sciences, then, chemistry follows a process which is generally agreed to lead to solid, verifiable theories about the natural world. A chemist forms a hypothesis, or educated guess, about what will happen in an experiment; she or he then performs the experiment, carefully noting both the actions taken as well as the observed results; she or he then analyzes those results with an eye to whether the hypothesis was shown to be correct or false. Based on these notes, another chemist may then repeat the experiment, to judge whether the first attempt was a fluke, or even a fraud.