For 4,000 years chemistry has been essential to the development of mankind. Since the beginning of the Bronze Age, people have used chemical processes in smelting and glassmaking; early medicine and alchemy were intimately related; and chemistry played a key role in the reawakening of scientific interest during the Renaissance and in the Industrial Revolution. But above all, it is in the last 100 years that the influence of chemistry has exploded, so that it now touches every aspect of scientific knowledge and civilized living.
Most of the familiar products around us depend on the chemical industry. Modern transportation relies on synthetic rubber, refined metals, and high-energy fuels. The construction industry needs paints, pigments, alloys, cements, glasses, plastics, and ceramics. Our clothing and fabrics are increasingly manufactured from artificial fibers such as nylon and polyesters, colored by synthetic dyes, and cleansed by synthetic detergents and solvents. Fertilizers, antifreezes, disinfectants, pesticides, cosmetics, adhesives, and drugs are just a few of the other products of synthetic chemistry.
The atomic theory of matter
The vital breakthrough that allowed chemistry to become the central science was the demonstration of the atomic nature of matter. In about 1800 John Dalton realized that all matter is composed of relatively few elements. He postulated that these elements combine together in accordance with their valency to make up discrete molecules. (Thus, water, H20, is formed by the combination of two hydrogen atoms with one oxygen atom.) Antoine Lavoisier proved that burning is simply the chemical combination of the combustible material with the oxygen of the air. In the early nineteenth century, Friedrich Wohler synthesized urea from inorganic materials and demonstrated that there is no difference in principle between inanimate substances and those of living matter.
The atomic theory allows us to treat all the properties of matter in terms of the molecules that make it up. This has enabled the development of chemistry (and physics) to progress rapidly. An explanation in terms of molecular structure allows scientists to carry out rational experiments to test the explanations. Furthermore, correct explanations of significant and desired properties lead to the possibility of predicting improvements to those properties by molecular modification. This, in turn, then allows additional experiments to produce materials with such improved properties.
This chain of events is the basis of all applied research, and the chief reason why living standards have so improved that in the developed nations the good life should now be possible for everyone.
За 4000 років хімії відіграли істотну роль у розвитку людства. З початку бронзового століття люди використовували хімічні процеси в плавки і glassmak-ня; рано медицині та алхімії були тісно пов'язані і хімії зіграли ключову роль у пробудженні наукового інтересу в епоху Відродження і в промисловій революції. Але, перш за все, саме в останні 100 років, що вплив хімії вибухнув, так що тепер зачіпає всі аспекти наукового знання і цивілізованого життя.
Більшість знайомих продуктах навколо нас-де залежати від хімічної промисловості. Сучасні транспортуванні спирається на синтетичний каучук, метал, і високої енергії палива. Будівельна галузь потребує фарби, пігменти, сплавів, цементу, скла, пластмаси та кераміки. Наш одяг і тканини стають все більш вироб-захопленого зі штучних волокон, таких як нейлон і поліестер, пофарбовані синтетичними барвниками і очистив від синтетичних миючих засобів і розчинників. Добрива, антифризи, дезінфікуючих засобів, пестицидів, косметика, клеї та препарати знаходяться всього в декількох інших продуктів синтетичної хімії.
Атомна теорія матерії
Життєво прорив, який дозволив хімії, щоб стати центральним наука демонстраційного атомної природи матерії. У близько 1800 Джон Дальтон зрозумів, що вся матерія складається з відносно невеликої кількості елементів. Він припустив, що ці елементи об'єднуються, щоб разом, у відповідності з їх валентністю скласти дискретних молекул. (Таким чином, вода, H20, утворюється комбінація з двох атомів водню з одним атомом кисню). Антуан Лавуазьє довів, що горіння це просто хімічна сполука горючого матеріалу з киснем повітря. На початку дев'ятнадцятого століття, Фрідріх Велер синтезували сечовину з неорганічних матеріалів і показали, що не існує принципової різниці між неживих речовин і тих, хто живої матерії.
The atomic theory allows us to treat all the properties of matter in terms of the molecules that make it up. This has enabled the development of chemistry (and physics) to progress rapidly. An explanation in terms of molecular structure allows scientists to carry out rational experiments to test the explanations. Further-more, correct explanations of significant and desired properties lead to the possibility of predicting improvements to those properties by molecular modification. This, in turn, then allows additional experiments to produce materials with such improved properties.
This chain of events is the basis of all applied research, and the chief reason why living standards have so improved that in the developed nations the good life should now be possible for everyone.
Chemistry and the biological sciences
In the last 50 years, chemistry has become the language of the biological sciences and the basis of many of its most important experimental theories and methods. For example, reproduction is central to the concept of living matter. Since James Watson and Francis Crick broke the genetic code in the late 1950's, we understand in molecular terms how information is passed from one generation to another. Genes are made up of nucleic acids; nucleic acids allow the synthesis of proteins in living organisms; and proteins are the universal catalysts for the chemical processes that make up life.
The science of molecular genetics—literally genetics explained by chemistry—has already had great influence on world food production through the development of new improved strains of crop plants and farm animals. And much more progress lies just ahead.
Biochemistry—the chemistry of life
Biochemistry is the branch of organic chemistry that deals with the processes that take place in living matter. Physiology—plant, animal, and human—is increasingly expressed in biochemical terms. Today we know that blood carries oxygen around the body in chemical combination with the protein hemoglobin. We
describe the working of nerves through chemical transmitters of known molecular formulae. Hormones are chemical messengers that monitor and control glandular functions. And the importance of the sodium-potassium balance in cell fluids is now well recognized.
Much of medicine is also dominated by chemical concepts. Medicinal chemists and pharmacologists design new pharmaceuticals for the control of diseases with reference to the molecular fitting of agent and protein receptor sites. In this way, the catalytic activity of the protein can be modified in the required direction. The recognition that sulfonamide drugs mimicked paraaminobenzoic acid derivatives led the way to the eradication of such infections as pneumonia. Present targets are the conquest of cancer and the understanding of the aging process.
The importance of inorganic chemistry
Inorganic chemistry is beginning to repay the great debt it owes to physics. Materials science is now based on molecular structure. The great advances in physics, electronics, and engineering would be impossible without semiconductors, transistors, and new magnetic materials—all crafted by chemical processes. Astronomy relies increasingly on chemical concepts. A knowledge of the chemical composition of the planets, interstellar matter, and the stars themselves is vital to test cosmological theories.
The geology of our planet earth has been largely determined by chemical reactions in the formation of rocks. Much weathering is caused by chemical processes, particularly reactions with water and with carbon dioxide and oxygen from the atmosphere.