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
The white smokepouring from the engine exhausts of aerobatic aircraft consists of finely divided titanium dioxide. This metallic compound also finds uses in electronic components and in paint and paper making. The preparation and properties of metals and their compounds are part of the study of inorganic chemistry.
Gummy resinseeping from the seed pods of opium poppies contains morphine and related compounds. They belong to a group of plant-produced chemicals known as alkaloids. Like most other drugs and physiologically active substances, alkaloids are dealt with in organic chemistry.
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.
Date: 2015-12-11; view: 1128