Fundamental substances

Mercury has been known for many centuries, perhaps because its extraction is easy it has an almost unique appearance, it readily displaces gold from its ores and it forms amalgams with many other metals—all properties which caused the alchemists to regard it as one of the fundamental substances. 

In this review, structural information on sulfoxides and sulfones is presented with emphasis on recent results and on structural variations. It is our intention that the discussion reflect the characteristic patterns of this area rather than provide an encyclopedic coverage. However, for the simplest, most fundamental, substances we are aiming at complete coverage as well. 

The modern science of chemistry began during the eighteenth century, when several brilliant natural philosophers classified the products of decomposition into a small number of fundamental substances. For example, in 1774, the Englishman Joseph Priestley discovered that when the red powder mercuric oxide was heated, it decomposed to liquid metal mercury and to a colorless gas capable of supporting combustion. (This gas... 

Elements are fundamental substances that cannot be broken down into smaller chemical components. The smallest unit of an element is an atom, a term based on the Greek word atomos, meaning indivisible. But atoms are divisible—they consist of a nucleus containing positively charged particles called protons and electrically neutral particles called neutrons, surrounded by a swarm of electrically negative particles called electrons. In chemical reactions, atoms interact and combine to form a molecule of a compound. (Chemical reactions also occur when the atoms in molecules interact and combine to form even bigger com-... 

Early scientists and philosophers invested much effort in the search for the fundamental substance or substances—the simplest kind of matter that comprises the world and all of its various materials. The ancient Greek philosopher Thales (ca. 635-556 b.c.e.) postulated that water is the fundamental substance. Although this idea may not sound realistic today, the hypothesis was a reasonable one. Life depends on water and Earth contains a huge quantity of water in oceans and rivers water falls from the sky as rain and seeps through the ground in wells. The ancient Greek philosopher Empedocles (ca. 495-435 b.c.e.) expanded the list of fundamental substances to four—water, earth, air, and fire. 

Thales of Miletus (c.620-c.555 bc), one of the first known enquirers into the constitution of the physical world, posited only one fundamental substance water. There is ample justification for this view in myth the Hebrew god was not the only deity to bring forth the world from a primal ocean. But the Milesian school of philosophers that Thales founded produced little consensus about the profe hyle or first matter that constituted everything. Anaximander (c.6ll-547 bc), Thales successor, avoided the issue with his contention that things are ultimately made of apeiron, the indefinite and unknowable first substance. Anaximenes (d. C.500 bc) decided that air, not water, was primary. For Heraclitus (d. 460 bc), fire was the stuff of creation. 

Plato s elements can be interconverted because of the geometric commonalities of their atoms . For Anaxagoras, all material substances are mixtures of all four elements, so one substance changes to another by virtue of the growth in proportion of one or more elements and the corresponding diminution of the others. This view of matter as intimate blends of elements is central to the antiquated elementary theories, and is one of the stark contrasts with the modern notion of an element as a fundamental substance that can be isolated and purified. 

Everything you see around you is formed from one or more of 114 presently known elements. An element is a fundamental substance that can t be chemically changed or broken down into anything simpler. Mercury, silver, and sulfur are common examples, as listed in Table 1.1. 

Compact bone like long bones, most abundant among archaeological bone remains, shows basically two different parts a central one called diaphysis, mainly composed of compact bone, and two extremities called epiphysis which are more porous. It contains a fundamental substance - a mixture of the organic and mineral phase - and cells that remodel continuously the bone material as well as the so-called Haversian systems containing channels that provide the nutrition to the bone cells as they accommodate blood vessels and nerves. The Haversian channels exhibit diameters between 10 and 70 pm [26], The periosteum closes the bone at its outside and the medullar cavity at the inside accommodating the bone marrow [40],... 

The substitution of two or three hydrogen atoms of methane by six-membered nitrogen heterocycles, like pyridine, quinoline, or benzoquinoline, leads to a class of compounds which we call quinolylmethanes, as its representatives are in structure as well as in their chemical and physical properties similar to di-(2-quinolyl)methane, the compound prepared first.1 Substitution of the central —CH2— (or =CH—) bridge by —NH— (or =N—) leads to the corresponding quinolylamines. Quinolylmethanes and quinolylamines are the fundamental substances of many cyanine dyestuffs. 

For ages, humankind has been interested about the structure of substances. For centuries, thinkers, philosophers, alchemists, and scientists have all tried to discover the most fundamental unit of matter. How is matter made up What are its fundamental substances How are its structures In the past, the answers to these questions were not easy to formulate. Let s try a simple exercise in order to better understand just how hard this must have been ... 

The Greeks were the first to try to explain why chemical changes occur. By about 400 b.c. they had proposed that all matter was composed of four fundamental substances fire, earth, water, and air. The Greeks also considered... 

Another approach to the study of the interstellar medium includes experiments carried out here on the Earth s surface. In such experiments, researchers attempt to simulate the conditions found in various regions of the ISM and to determine if chemical reactions hypothesized for those regions actually do occur. The study by scientists at SETI and NASA on amino acids, reported earlier in this chapter, is an example of such experiments. Researchers general approach in such experiments is to enclose certain fundamental substances (such as hydrogen, oxygen, and carbon monoxide) within a sealed container at the low temperatures and pressures common to the ISM and then expose those substances to the type of radiation that may be found in some particular region of the ISM, such as ultraviolet radiation or cosmic-ray-like radiation. The substances formed in such experiments can then be compared with those actually observed in the ISM. 

Chitin, a polysaccharide similar to cellulose, is Earth s second most abrmdant polysaccharide (after cellulose). It is present in the cell walls of fungi and is the fundamental substance in the exoskeletons of crustaceans, insects, and spiders. The structure of chitin is identical to that of cellulose, except for the replacement of the OH group on the C-2 carbon of each of the glucose units with an -NHCOCH3 group. The principal source of chitin is shellfish waste. Commercial uses of chitin waste include the making of edible plastic food wrap and cleaning up of industrial wastewater. 

Chitin, the earth s second most abundant polysaccharide, is the fundamental substance in the exoskeletons of crustaceans. 

We have seen that all matter exists as elements or can be broken down into elements, the most fundamental substances we have encountered up to this point. We will have more to say about the nature of elements in the next chapter. 

The ancient Greeks believed that all matter was composed of four fundamental substances earth, air, fire, and water. How does this early conception of maffer compare with our modern theories about matter ... 

We have seen that the matter around us has various levels of organization. The most fundamental substances we have discussed so far are elements. As we will see in later chapters, elements also have structure They are composed of atoms, which in turn are composed of nuclei and electrons. Even the nucleus has structure It is composed of protons and neutrons. And even these can be broken down further, into elementary particles called quarks. Flowever, we need not concern ourselves with such details at this point. Figure 1.14 summarizes our discussion of the organization of matter. 

The Greeks were the first to try to explain why chemical changes occur. By about 400 B.c. they had proposed that all matter was composed of four fundamental substances fire, earth, water, and air. The Greeks also considered the question of whether matter is continuous, and thus infinitely divisible into smaller pieces, or composed of small, indivisible particles. Supporters of the latter position were Demokritos of Abdera (c. 460-c. 370 B.c.) and Leucippos, who used the term atomos (which later became atoms) to describe these ultimate particles. However, because the Greeks had no experiments to test their ideas, no definitive conclusion could be reached about the divisibility of matter. 

There are two kinds of pure substances elements and compounds. An element is a substance that cannot be separated into simpler substances by ordinary chemical methods. Nor can it be created by combining simpler substances. All the matter in the universe is composed of one or more of these fundamental substances. When elements are combined, they form compounds—substances having definite, fixed proportions of the combined elements with none of the properties of the individual elements, but with their own unique set of new physical and chemical properties. 

As we examine the chemical changes of matter, we encounter a series of fundamental substances called elements. Elements cannot be broken down into other substances by chemical means. Examples of elements are iron,... 

We can summarize the desaiption of matter given in this chapter with the diagram shown in Figure 3.10. Note that a given sample of matter can be a pure substance (either an element or a compound) or, more commonly, a mixture (homogeneous or heterogeneous). We have seen that all matter exists as elements or can be broken down into elements, the most fundamental substances we have encountered up to this point. We will have more to say about the nature of elements in the next chapter. 

What were the four fundamental substances postulated by the Greeks ... 

An element is a fundamental substance that cannot be broken down into simpler substances by chemical methods. An element consists of atoms of only one type. Compounds, on the... 

In a chemical sense, fats are triglycerides. This word may sound familiar to maiy as it is often used in the mass media. In blood tests, the level of triglycerides is often measured in addition to cholesterol. Triglycerides are compounds formed from glycerol (an alcohol with three hydroxyl groups) and fatty acids known as esters. They are fundamental substances in all living organisms, bacteria and humans alike. 

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