By Karel Kosman 
Chemistry is the science of substances, or materials, their composition and characteristics, and the reactions which take place between those substances. It is concerned with chemical elements in their pure state and when they are combined, that is, reactions of these elements and the compounds which they form. The scientist who wants to do chemistry must first be able to understand its building blocks, substances in their pure state. Only then can the chemist use that knowledge to comprehend more complicated phenomena, and begin to perform his own experiments.
Every chemical reaction can be represented with the help of atoms and molecules. It was necessary, therefore, to develop a special system of chemical symbols. Substances in their pure state, called elements, were sometimes named after the scientists who discovered them. From those names, abbreviations were derived (like O for oxygen). These chemical symbols are used to denote various chemical reactions. Every element, then, has a letter or letters associated with it, most of these coming from the element's Latin name. It is natural that each element has its own original abbreviation.
With the help of these chemical symbols, which contain both letters and numbers, chemical reactions can be described in a way which describes the reality of what takes place at the atomic level. On one side, the left, are reactants, the substances which enter into a reaction. On the right side are products, the end results of a reaction.
Chemistry deals with reactions at the atomic level of substances. It attempts to experimentally decipher what happens between the individual atoms of a reaction, the "secret" of each reaction. In turn, these secrets help chemists formulate chemical laws and scientific information, which help them to better understand the world around us. One of the goals of chemistry is the development of new substances and materials, and their production. With the help of these new materials, those already in use can be replaced by more effective, higher quality ones, to make our lives easier and better.
In our daily lives, chemistry can be found around every corner. Without commercial fertiliser, medicines, plastics and other chemical products, it would be difficult to imagine our lives as they are today. We human beings have chemistry to thank for the tablets we take to make us feel better, for cleaning products, as well as for cosmetics and foods and other grocery products which contain preservatives to make them last longer.
Of course, what seemed to be promising chemical discoveries can also be the cause of environmental disasters. For example, DDT (dichlorophenyltrichloretane), an insecticide, or freon (composed of flourine and chlorine with hydrocarbons), and the dissolved gases in aerosol sprays and cooling fluids for refrigerators have all caused problems. When these problems arise, however, it is chemistry which has to step in to offer a solution.
A good example of this process, getting rid of harmful substances with the help of chemistry, was the development of a catalytic converter for motor vehicles. This device is simply an improvement to the exhaust system of motor vehicles. With its help, a highly poisonous gas, carbon monoxide (chemical symbol CO) is changed into the less harmful molecule carbon dioxide (chemical symbol CO2).
Chemistry's Beginnings
Many chemical reactions and procedures were being used long before human beings figured out that chemical laws actually governed their behaviour.
One example is the use of fire by early peoples as a source of light and heat: This is an oxidation reaction taking place.
The real beginnings of chemistry must be attributed to the developed cultures of times past. We can assume that the Egyptians, as well as the Chinese and ancient Greeks, were at the centre of the progress made in olden times. The inventions and discoveries made back then were often revolutionary, like the invention of gunpowder, which the Chinese discovered in the year 900 A.D. These discoveries often served to spark great progress in the field of natural sciences.
The ancient Greeks explained the nature of matter two different ways. Some claimed that all materials were made of four basic building blocks, or elements: air, water, earth and fire. Others believed that all materials were made up of incredibly minute particles, so-called atoms (Greek atomos = invisible). Chemistry as a science had first to be founded from a philosophical perspective. Only later could fields of study like metallurgy and alchemy be developed.
For a long period of time, alchemy concerned itself with the discovery of what was then known as the "philosophers' stone". Alchemists attempted to turn simple metals, such as lead, into gold. This discipline came into being in the sixth century B.C. in Egypt. The word alchemy as such means "black element".
No documents exist that prove that the so-called philosophers' stone was ever discovered, but the amount and variety of experiments performed in the pursuit of changing metals to gold proved to be of great importance for the future of chemistry.
In the Middle Ages, chemistry began to have close ties with medicíne. Only a short time later, science began to be perceived as a series of factual and methodical processes, and old-style mythological beliefs slowly faded into the sunset. Antoine Lavoisier began the modern era of chemistry by proving the existence of "Oxygenia" through a combustion experiment.
The 18th century saw scientific progress accelerated in an unprecedented fashion. New elements were discovered. The foundations of both electrochemistry and organic chemistry were laid. And, scientists began to try to organise matter, or the elements, in a systematic way. In the end, it was Mendel and Meyer who found the answer in what is now known as the periodic table of the elements, which is in use to this day.
The discovery of molecular orbitals in the 20th century helped to explain covalent bonding. Thanks to that discovery, more and more synthetic products (artificially produced) were developed. In addition, one of the most revolutionary discoveries of recent history was the "untangling" of the structure of the DNA molecule, the building block of all organic matter.
Of course, chemistry is not a closed system, unrelated to others. It is only one segment of the spectrum of natural sciences, all of which are in constant flux, changing and being modified constantly.
Important events in the history of chemistry
3200 B.C. Egyptian scientists produce copper from ore with the help of fire and wooden coal.
3000 B.C. First glass objects made in Egypt and Mesopotamia.
425 B.C. Democritus comes up with the first atomic theory in Greece.
300 B.C. Philosopher chemists formulate the first theory that all matter is made of elements (in Greece: 4-100 elements, in China: 5 elements).
180 B.C. First alchemistry experiments publicised in Egypt.
Around 600 years from the first Egyptian alchemistry attempts, the science reaches the Arab world.
900 A.D. The Chinese discover gunpowder.
Organised religion, specifically the Catholic Church, resists any and all new discoveries, keeping inventors and scientists from publicising their theories. The development of chemistry is greatly slowed, if not made completely impossible.
1661 Robert Boyle casts doubt on classical models and comes up with a new definition of the "element".
1766 Henry Cavendish discovers hydrogen.
1782 Karl Sheele discovers oxygen, calling it the "spirit of fire". Joseph Priestley comes up with the same discovery independently two years later.
1782 Antoine L. Lavoisier discovers that matter is neither created nor destroyed in chemical reactions, the law of conservation of mass.
1783 Antoine L. Lavoisier shows that oxygen and hydrogen can be burned together to form water.
1799 Joseph L. Proust shows that elements always combine in certain constant proportions of their mass (the law of constant proportions).
1803 John Dalton proposes his atomic model.
1807 Humphry Davy performs the first electrolysis separation, of table salt, into calcium and sodium.
1828 Friedrich Wöhler synthesises an organic resin from inorganic reactants.
1860 Robert W. Bunsen and Gustav R. Kirchhoff first discover an element, cesium, using spectroscopy.
1871 Dimitrij Mendel and Lothar Meyer publish their periodic table of the elements.
1884 Svante Arrhenius comes up with the theory of electrolytic dissociation.
1909 Sven Peter Srensen introduces the pH scale.
1920s Crystal structures begin to be investigated through X-ray structural analysis.
1937 Emilio Sergré synthesises the first man-made element - technecium.
1939 Linus C. Pauling introduces the first broad, modern theory of organic bonding.
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