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Chemistry

Chemistry

A modern, albeit superficial, definition of chemis­try is that it is the science dealing with the compo­sition of substances, their properties and reactivity. All matter in the universe is composed of the chemical elements; their systematic study, and that of the compounds they form, is . Chemistry has earned itself the title of the central science, as the study of matter is fundamental to all other sciences, including physics, materials sci­ence, biology, and pharmacology to name just a few. Typical applications of chemistry in modern life include the discovery and development of new drugs; the discovery and production of fuels, plas­tics, fertilizers, pesticides, vaccines, and foods; the use of chemical techniques by forensic scientists to solve crimes; and the production of new materials and pigments for the clothes we wear and the many functional items in our homes. It is certain that chemistry has occurred since time began and will prevail until time ceases, and this makes the discussion of chemistry in time both fascinating and hugely important. The impact that the science of chemistry has had on humanity is huge. The ill-defined and semi-empirical beginnings of what we now know as the highly advanced, organized, and multidisciplinary science of chemistry lends well to a general overview of the subject being discussed within the framework of time.

Initially, the development of chemistry as a widely accepted scientific discipline from its rather chaotic foundation in and is discussed from a historical perspective, with par­ticular emphasis on the scientific, technological, global, and economic impact from its initial estab­lishment in the 16th century to the present day. Next, the position and influence of chemistry in the 21st century is introduced by a retrospective exposition of the effect of chemistry on humanity and the environment. The subsequent expansion alludes to the challenges within chemistry itself as both the source of, and solution to, many funda­mental problems that currently face humanity, and that will most certainly become more pressing and severe in the near future.

Chemistry in the Past

Around the 7th century BCE, is credited as the first of the Greek philosophers who endeavored to explain the natural world around him without invoking any supernatural phenom­ena. Indeed, he is arguably the first scientist. The Greeks explained many natural occurrences, such as lightning and earthquakes, as the direct interven­tion of anthropomorphic gods and heroes. Such mythological reasoning was sidelined by Thales and he instead proposed, for example, that the earth floats on water, and hence the occurrence of earth­quakes can be explained by the striking of the earth by waves of water. Thales held the view that all matter was ultimately derived from water, although this hypothesis was certainly tainted with the super­natural. Thales’ Miletian philosophical descendants were more coy: Anaximander ascribed to all sub­stances being made from apeiron, a single, unknown substance. Subsequently, air (Anaximines) and fire (Heraclitus) were separately proposed to be the basic constituent of all matter.

The quest by philosophers to produce a simple explanation of the natural world, combined with the observation that one substance could be con­verted into another, meant the idea that all sub­stances were ultimately composed of the same basic building block was attractive and persisted for some time.

Aristotle (c. 4th century BCE) agreed with the notion that ultimately there was only a single primal substance, but argued that it was incompre­hensible to humankind. Somewhat contradictorily, he believed that Empedocles’ four elements—earth, air, fire, and water—were the constituents of all matter. He was also sympathetic to Anaximander’s view that the phenomena of heat, cold, wetness, and dryness were influential in the interconversion of different substances; a view not alien to our modern-day understanding of the transformations between states of matter with, for example, water converting from a solid to a liquid to a gas by heat­ing; the process being reversed by cooling.

Leucippus is believed to have formulated the idea that all matter is made of many small parti­cles, or atomos (a term coined by Democritus, meaning “indivisible”), all of which are made of the same primal substance, but are observed differ­ently depending upon the material. These ideas were made to be compatible with Aristotle’s “quartet of elements.” There was disagreement between proponents of and those of the older theories. Opponents of Leucippus wanted to know what he claimed might separate these small particles if they were really indivisible?

Empedoclean views of the four elements consti­tuting matter, which was supported by the credible figure of Aristotle, eventually led to the suppression of atomism as a credible explanation for the compo­sition of the natural world. Its perceived blasphe­mous stance was condemned in the Middle Ages, though it did not disappear completely. It was the experimental input from alchemy, rather than con­jecture, that progressed our understanding to what we know and accept today.

Although alchemy has long been regarded as pseudoscientific, that is, a practice that claims to be scientific but does not adhere to the scientific method (the proposition of a hypothesis based on a natural phenomenon that is then tested experi­mentally in an objective and transparent manner), it is the forerunner of chemistry as we know it today.

Closely related to the ancient traditions of Hermeticism, Western alchemy is often viewed as a practice akin to black magic, with practitioners intent on producing gold from a variety of tenuous, mystically based recipes and incantations. This view is somewhat dispelled, however, when it is considered that many of those who practiced alchemy went on to influence much of what is now called modern science, Isaac Newton and Robert Boyle being two examples. In fact, over the course of the early modern period, mainstream alchemy developed into a discipline now recognizable as the precursor to modern chemistry.

A cursory examination of alchemy and its metamorphosis into a rigorous scientific discipline follows. It is significant that it predates the philo­sophical musings of the ancient Greeks by a con­siderable margin.

It is believed that “Western alchemy” origi­nated in Egypt (5000-400 BCE) and subsequently became established in Greek and Arabian civiliza­tions, and in Europe from 1300 onwards. Chinese and Indian alchemy were developed independently and remain culturally isolated.

The proliferation of alchemy was motivated by spiritual beliefs that were connected to unexplained and enchanting physical phenomena, such as fire: a mystical force that could transform one sub­stance into another. In the same way compounds are broken down and recombined by the alche­mist, it was believed that the immortal spirit was separated from the mortal body upon death, and recombination with matter meant immortality. The search for an elixir of life was closely linked to the ongoing challenge of being able to transmute poorer base metals into gold. By the same token, the alchemist sought the perfection of the self, with death not seen as the end.

During the Renaissance, the ideas of Rene Descartes and Roger Bacon provided the founda­tions for developing the scientific method. Around this time, Western alchemy began to split into two separate strands. Initially, it was Paracelsus who directed alchemy away from the underlying mystical and spiritual influences and applied a more scientific approach, giving rise to iatrochemistry. However, there remained those who held firm to the spiritual foundations of alchemy and continued the search for immortality and metal transmutation.

It has been said that the development of metal­lurgy (which is inextricably linked with alchemy) was the turning point in history that marked a departure from the Aristotelian elements. The met­als, of which a significant number had been discov­ered by the 17th century, were regarded as “earth,” an extrapolation of the notion that the known states of matter corresponded to the physical form of a substance: “air” was gas, “water” was liquid, and “earth” was solid. The cultural importance of gold was increasing, and its obvious difference from the other metals was of great interest, there­fore the notion of them being “the same” was unacceptable.

The vague and esoteric language of alchemy, the irreproducibility of experiments, and the exposure of fraudulent practice began to frustrate eminent writers such as Geoffrey Chaucer and Dante Alighieri. Alchemists were accused of delib­erately trying to conceal their methods from the uninitiated, and their opponents argued that they were in fact self-deceived; skepticism and distrust toward alchemy became popular opinion.

The publication of The Sceptical Chymist by Robert Boyle in 1661 became a cornerstone in the development of chemistry away from its alchemical roots. Boyle refuted the concept of Aristotle’s quar­tet of elements, instead contending that all sub­stances were made of irreducible particles of some shape or form. An important point is that he argued that a proposed theory must be proved by experi­mentation before it could be accepted as true. Subsequent work in the 18th century by Antoine Lavoisier paved the way for the chemistry we know today. He concluded, rightly so, that water and air were composed of distinct entities, and thus they were not elements at all. Lavoisier also took the significant step of quantitatively measuring his experiments, allowing him to demonstrate mass changes during combustion. Crucially, the identifi­cation of oxygen was achieved, though it is certainly debatable whether Lavoisier was the first to dis­cover this element. Joseph Priestley was instrumen­tal in corroborating the work of Lavoisier.

At the turn of the 19th century John Dalton is to be credited with the revival of a modern atom- ist theory: Elements are made of small particles called atoms; all the atoms of a given element are identical to each other but different from those of another element; atoms from one element can combine with those of another in a fixed propor­tion; and they cannot be created or divided into simpler particles. He implemented a system for depicting the known chemical elements of that time (though some were erroneous as, in fact, they were chemical compounds) and, most important, gave them a measurable quantity: atomic weight. Jöns Jakob Berzelius proposed the designation of simple symbols for the chemical elements, for example, F for fluorine and Mg for magnesium. This is the modern-day language of chemistry.

Many were now to attempt the tabulation and systematic ordering of the known chemical ele­ments. It was Dmitri Mendeleev who studied the behavior of individual elements, grouped them together by virtue of similar chemical properties, and successfully predicted the existence of ele­ments that were discovered during his lifetime. This culminated in the much-vaunted periodic table of elements, today’s ’s “road map” to all the known chemical elements.

It now remained for the conclusive identifica­tion of atoms themselves as being the true “primal matter.” In 1909, Ernest Rutherford chose gold with which to perform his experiments to deter­mine to composition of the atom. Being malleable, it could be beaten into very thin sheets, which made it almost transparent. Firing a-particles (positively charged helium nuclei) at thin gold foil afforded some very surprising observations. The refinement of Rutherford’s results by Niels Bohr, coupled with Joseph John Thomson’s earlier dis­covery of the electron, and the subsequent discov­ery of the neutron by James Chadwick in 1932, led to the establishment of the currently accepted view of the atom. It consists of a dense, positively charged nucleus of two distinct subatomic parti­cles, protons and neutrons, surrounded by a cloud of negatively charged electrons, with the two sepa­rated only by empty space (an idea intolerable to most early Greek philosophers).

Chemistry in the Present
and Looking to the Future

The development of chemistry from the early attempts by philosophers to understand their surroundings to the well-established and undis- putedly vital scientific discipline it is today has been key to the development of civilization across the globe. However, the influence of chemistry has been both positive and negative. While people are able to live longer and more comfortably thanks to improvements in agriculture (fertilizers and pesticides), pharmaceuticals, and energy derived from crude oil, the improvement in our quality of life has impacted negatively upon the environment through, for example, global warming, the deple­tion of the ozone layer, and pollution of terrestrial water systems. Numerous human tragedies have arisen through the irresponsible or malicious use of chemicals: the Bhopal disaster; the deployment of nerve and blister agents during warfare; and the prescription of thalidomide to pregnant women to name but a few. Chemistry and the chemical industry are certainly sometimes viewed with sus­picion, and the dogma that “natural” substances are “good” and those produced by man are “bad” persists. Certainly a prominent challenge for the future is to educate the general public; ignorance is perhaps the fault of chemists and other scientific disciplines for allowing themselves to be viewed as impenetrable.

Chemistry today is very much at the forefront of technological development and it is studied intently in academic and industrial institutions. Research efforts are directed toward both blue-sky exploration and the addressing of specific scien­tific problems. The discovery and development of new chemical reactions and techniques have ele­ments of both, whereas the preparation of new chemical elements by nuclear chemistry and the development of sustainable energy alternatives are restricted to each category, respectively.

Perhaps surprisingly, alchemy, the transmuta­tion of elements, is still an actively pursued area of research. The prospects for the isolation of the heavier nuclei of elements with an atomic number greater than 118 appear to be very challenging.

Humankind’s desire to understand and predict the properties of molecules has been unrelenting. The application of quantum mechanical methods to the study of a chemical system has made the most of the improvements in computing power. Chemists are still currently limited to the study of comparatively simple systems under artificial conditions. For example, most density functional calculations on molecules to probe their stability and geometry are performed in the gas phase, with interaction between other molecules unac­counted for. As computers become more power­ful, chemists will be able to study the structure of more complex molecules (invariably those that play a key role in biochemistry) and probe their interaction with one another.

Nature has remained far superior in its elegance and efficiency in producing useful chemicals. Humankind has marveled at the complexity of pho­tosynthesis, respiration, and the fixation of atmo­spheric nitrogen for decades. Attempts to model these systems in the laboratory using a much more basic repertoire of chemicals have met with only limited success. Such attempts have, however, broad­ened our understanding of these natural processes considerably. The industrial production of bulk chemicals is costly both in terms of energy and its impact on the environment. The development of a process to produce ammonia with the comparable mildness and efficacy of the nitrogenase family of enzymes would make a welcome replacement for the Haber process. Similarly, the cheap and environ­mentally benign production of hydrogen to be used as an energy source is highly sought after. The increasing levels of carbon dioxide in the atmo­sphere, generated from the combustion of fossil fuels, are largely responsible for global warming. The sequestration, or ideally, utilization of CO2 as a feedstock itself is highly desirable.

Similarly, some the most efficacious medicinal compounds are those isolated from natural sources, but they tend to be highly complex structures and very difficult to make in the laboratory. The ingenu­ity of synthetic chemists means that, given enough time and resources, any molecule can be made in the laboratory. But this process is inefficient and expen­sive, and largely serves to showcase what chemists can achieve rather than resulting in a useful prod­uct. Given the dwindling success of the pharmaceu­tical industry in generating new medicines, the future will see a renaissance of drugs being devel­oped from natural products. Instrumental in this process will be the crafting of genetic engineering, rendering bacteria, rather than chemists and glass­ware, the far better choice for producing potential new drugs on the scale likely to be required.

Astrochemistry, the application of chemical techniques to the study of the chemistry in outer space, has afforded interesting insights into the universe itself and its influence on the formation and the development of planet Earth. Many hypotheses have been put forward to suggest that life as we know it, or at least its simple organic precursors, could have developed in space and then subsequently been transferred to Earth by meteorites. Chemistry will continue to be of immense value to space exploration, and it is hoped that it will provide more clues as to our origin, and maybe even our subsequent fate.

James V. Morey

See also Aristotle; Chemical Reactions; Comets; Decay, Organic; DNA; Dying and Death; Ecology; Evolution, Chemical; Life, Origin of; Medicine, History of; Meteors and Meteorites; Oparin, A. I.; Paracelsus; Photosynthesis; Presocratic Age; Space Travel; Thanatochemistry

Further Readings

Ball, P. (2003). Molecules: A very short introduction. Oxford, UK: Oxford University Press.

Ball, P. (2004). The elements: A very short introduction. Oxford, UK: Oxford University Press.

Donovan, A. (1993). Antoine Lavoisier: Science, administration, and revolution. Cambridge, UK: Cambridge University Press.

Greenberg, A. D. (2000). Chemical history tour, picturing chemistry from alchemy to modern molecular science. New York: Wiley-Interscience.

Hall, N. (Ed.). (2000). The new chemistry. Cambridge, UK: Cambridge University Press.

Lewis, F. A. (1991). Substance and predication in Aristotle. Cambridge, UK: Cambridge University Press

Robinson, J. M. (1968). An introduction to early Greek philosophy. Boston: Houghton Mifflin.

Scerri, E. R. (2006). The periodic table: Its story and its significance. Oxford, UK: Oxford University Press.

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Chemical Reactions

Chemical Reactions

Chicxulub Crater

Chicxulub Crater