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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.

Biochemistrythe 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.