restricted access What Is Chemistry?
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What Is Chemistry? F. Jon Kull Chemistry is the science of understanding the properties of matter and how matter forms from the basic elements that make up our universe.Chemists seek to understand how the atoms and molecules that make up matter can combine, how and when they react, and how new molecules can be synthesized. Chemistry can explain why water freezes at some temperatures, but remains liquid at others.It can explain why wood is so stable that buildings made from it can last for hundreds of years, yet a single match can reduce it to ashes. It enables us to make the drugs that keep us healthy and the polymers that shape our society. Chemistry helps us understand the basic principles of life, how proteins fold, and how DNA carries the code to make a human being. In short, chemistry helps us to understand many of the natural world’s most fascinating questions. Although chemistry is often called the central science, I think of chemistry as occupying an arc in a great circle of disciplines that help us understand the world we live in.To one side, chemistry is flanked by physics, beyond which is math; and I think many would agree that math edges up against philosophy. On the other side, chemistry blends into biology, beyond which is physiology, and,for humans,psychology,sociology,and,you guessed it,philosophy.So don’t think of any of these fields as distinct; they are related to each other and merge into each other. You can start your journey of understanding our world at any point on the circle. A Brief History of Chemistry People have been fascinated with the reactions of matter for thousands of years, and the Greek philosophers were perhaps the first to try to define the nature and makeup of matter. In Aristotle’s view of the world, four basic elements—earth, What Is Chemistry? 75 air,fire,and water—could be combined to form everything in the universe.This view was accepted as truth for centuries,with some slight modifications.By the 1600s,alchemists were studying materials and reactions,seeking to change matter into different forms (particularly lead into gold), and trying to create ever more perfect materials. They believed that all complex matter, for example wood or flesh, could be broken down into three basic elements: salt, mercury, and sulfur. Among the alchemists was a young man whom many believe to be the first chemist, Robert William Boyle (1627–1691). Boyle had the clarity of thought to think beyond the common practices and beliefs of Aristotle and the alchemists and to approach the study of matter using the scientific method, which is based on hypothesis, experimentation, and logical analysis. Much of this is described in his 1661 book The Sceptical Chymist, in which he describes his skepticism, not of chemistry,but of the common premises of alchemy.The book is a fascinating read, and describes the observations and experiments Boyle conducted which convinced him that the beliefs of the alchemists were incorrect and that matter was composed of far more elements, which he called “corpuscles.”For example, Boyle did not believe that gold,which was so pure and beautiful,could be made up of some combination of salt, mercury, and sulfur. In one experiment, Boyle had his gardener gather some soil and dry it in an oven. He then planted a “pompion”(i.e., pumpkin) seed, watered it using only rainwater, and let it grow over the summer.In the fall,he determined the mass of the plant and pumpkin, as well as the dry mass of the remaining soil. He was amazed to find the soil’s mass had not decreased, and deduced that somehow the plant matter had been formed only from the water that was added.Of course,this presented a problem for him, as the same water and soil could produce a number of different plants, from which could be derived a variety of oils. Boyle knew there must be more going on than the alchemists could explain, and devoted his life to the study of this and other reactions, founding what is considered to be modern chemistry. Of course, today we know that plants use not only water, but also carbon dioxide from the air, to grow, and that they do indeed extract some nutrients from the soil. However, at the time Boyle had not yet imagined that the air contained different molecules, and he does not even mention...