Early thinking about Materials

People working with their hands have undoubtedly sometimes asked the question What is matter in reality In Greek culture some philosophers occupied themselves with thinking about matter. How is matter built up In the 5 century bc different opinions were formulated. 

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The discovery in the 1980s that RNA molecules often have catalytic properties and may serve as true enzymes (ribozymes Chapter 12) stimulated new thinking about evolution. Although RNA catalysts are not as fast as the best enzymes they are able to catalyze a wide variety of different reactions. Could it be that in the early evolution of organisms RNA provided both the genetic material and catalysts The "RNA world" would have been independent of both DNA and protein.a b Later DNA could have been developed as a more stable coding molecule and proteins could have evolved as more efficient catalysts. Plausible reactions by which both cytosine and uracil could have arisen in drying ponds on early Earth have been demonstrated.6... 

The idea of an element as a basic type of material, different from other materials, has been around for at least 2 million years, when the first people to make stone tools appeared on the scene. These early humans chose different types of rock for different tools, knowing that certain kinds of rock were more likely to break into small flakes or keep their sharp edge. Although they probably did not think about the building blocks of the rocks themselves, they knew that the material of some rocks was different from the material of other rocks. 

Perhaps the most significant distinction in the way people think about microtechnology and nanotechnology however, is not a matter of scale, hut a philosophy of materials science. For almost all of human history, people have made new products hy starting out with a hunk of material and hacking it down to just the right size and shape. Early humans used hard rock to chip hone, wood, and other materials into arrows and spearheads. Today, complex machinery is used to hend, twist, cut, meld, and otherwise shape aluminum, steel, and other materials into automobile bodies, skyscraper skeletons, refrigerators, and other objects. 

When thinking about how our solar system may have evolved from proplyds (protoplanetary disks), we must remember that the violence of the early Solar System was tremendous as huge chunks of matter bombarded each other. In the inner Solar System, the Sun s heat drove away the lighter-weight elements and materials, leaving Mercury, Venus, Earth, and Mars behind. In the outer part of the system, the solar nebulas (gas and dust) survived for some time and were accumulated by Jupiter, Saturn, Uranus, and Neptune. 

If you look at the miscellany of Victorian objects shown in Figure 1-4, molded from a material called Parkesine in the early 1860s, you may not be impressed. But, think about it for a while. What if the ordinary things of everyday life, buttons, combs, toothbrushes,... 

After thinking about the phenomena of electrolysis (which we shall discuss in Chap. 10), an English scientist. Dr. G. Johnstone Stoney, stated, as early as 1874, that these phenomena indicate that electricity exists in discrete units, and that the units are associated with material atoms. In 1891 he emphasized this point and suggested the name electron for the postulated unit of electricity. At that time experiments were being carried on by physicists on the conduction of electricity through gases (as in a neon lamp) these experiments after some years (in 1897) led Sir J. J. Thomson (1856-1940), then Director of the Cavendish Laboratory at Cambridge University, to the firm conclusion that the electron exists and to the determination of some of its properties. 

Let s think about aluminum in this context. Pure aluminum is never found in namre. Instead, the metal occurs in an ore, called bauxite, that is composed of both useless rock and aluminum in combination with oxygen. So before aluminum can be used in our soda can, it must first be extracted or won from its ore and purified. Because aluminum combines very readily with oxygen, this presents some serious challenges. Some of these challenges are chemical and will be revisited in Chapter 13 of this text. Some of the early steps, however, can be solved by clever applications of physical properties, and we will consider a few of them as we investigate introductory material in this chapter. When confronted with a complex mixture of materials, such as an ore, how does a chemist think about separating the mixture ... 

Earths core is a solid iron sphere about the size of the Moon. Surrounding the inner core, there is an outer liquid core that contains a nickel-iron alloy. Scientists think the iron core formed when multiple collisions during Earths early history resulted in enough heat to melt metals. In the molten state, the densest materials, including iron and nickel, settled to the center and became Earths core. The less-dense materials remained at the surface. As Earth cooled, the outer layers solidified, creating Earths mantle and crust. 

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