1.
Chemistry
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Chemistry is a branch of physical science that studies the composition, structure, properties and change of matter. Chemistry is sometimes called the science because it bridges other natural sciences, including physics. For the differences between chemistry and physics see comparison of chemistry and physics, the history of chemistry can be traced to alchemy, which had been practiced for several millennia in various parts of the world. The word chemistry comes from alchemy, which referred to a set of practices that encompassed elements of chemistry, metallurgy, philosophy, astrology, astronomy, mysticism. An alchemist was called a chemist in popular speech, and later the suffix -ry was added to this to describe the art of the chemist as chemistry, the modern word alchemy in turn is derived from the Arabic word al-kīmīā. In origin, the term is borrowed from the Greek χημία or χημεία and this may have Egyptian origins since al-kīmīā is derived from the Greek χημία, which is in turn derived from the word Chemi or Kimi, which is the ancient name of Egypt in Egyptian. Alternately, al-kīmīā may derive from χημεία, meaning cast together, in retrospect, the definition of chemistry has changed over time, as new discoveries and theories add to the functionality of the science. The term chymistry, in the view of noted scientist Robert Boyle in 1661, in 1837, Jean-Baptiste Dumas considered the word chemistry to refer to the science concerned with the laws and effects of molecular forces. More recently, in 1998, Professor Raymond Chang broadened the definition of chemistry to mean the study of matter, early civilizations, such as the Egyptians Babylonians, Indians amassed practical knowledge concerning the arts of metallurgy, pottery and dyes, but didnt develop a systematic theory. Greek atomism dates back to 440 BC, arising in works by such as Democritus and Epicurus. In 50 BC, the Roman philosopher Lucretius expanded upon the theory in his book De rerum natura, unlike modern concepts of science, Greek atomism was purely philosophical in nature, with little concern for empirical observations and no concern for chemical experiments. Work, particularly the development of distillation, continued in the early Byzantine period with the most famous practitioner being the 4th century Greek-Egyptian Zosimos of Panopolis. He formulated Boyles law, rejected the four elements and proposed a mechanistic alternative of atoms. Before his work, though, many important discoveries had been made, the Scottish chemist Joseph Black and the Dutchman J. B. English scientist John Dalton proposed the theory of atoms, that all substances are composed of indivisible atoms of matter. Davy discovered nine new elements including the alkali metals by extracting them from their oxides with electric current, british William Prout first proposed ordering all the elements by their atomic weight as all atoms had a weight that was an exact multiple of the atomic weight of hydrogen. The inert gases, later called the noble gases were discovered by William Ramsay in collaboration with Lord Rayleigh at the end of the century, thereby filling in the basic structure of the table. Organic chemistry was developed by Justus von Liebig and others, following Friedrich Wöhlers synthesis of urea which proved that organisms were, in theory
2.
Ionic compound
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In chemistry, an ionic compound is a chemical compound composed of ions held together by electrostatic forces termed ionic bonding. The compound is overall, but consists of positively charged ions called cations. These can be simple ions such as the sodium and chloride in sodium chloride, or polyatomic species such as the ammonium, Ionic compounds containing hydrogen ions are classified as acids, and those containing basic ions hydroxide or oxide are classified as bases. Ionic compounds without these ions are known as salts and can be formed by acid–base reactions. Ionic compounds typically have high melting and boiling points, and are hard, as solids they are almost always electrically insulating, but when melted or dissolved they become highly conductive, because the ions are mobilized. The word ion is the Greek ἰόν, ion, going and this term was introduced by English physicist and chemist Michael Faraday in 1834 for the then-unknown species that goes from one electrode to the other through an aqueous medium. In 1913 the crystal structure of sodium chloride was determined by William Henry Bragg, many other inorganic compounds were also found to have similar structural features. Principal contributors to the development of a treatment of ionic crystal structures were Max Born, Fritz Haber, Alfred Landé, Erwin Madelung, Paul Peter Ewald. Born predicted crystal energies based on the assumption of ionic constituents, Ionic compounds can be produced from their constituent ions by evaporation, precipitation, or freezing. Reactive metals such as the alkali metals can react directly with the highly electronegative halogen gases to form an ionic product and they can also be synthesized as the product of a high temperature reaction between solids. If the ionic compound is soluble in a solvent, it can be obtained as a compound by evaporating the solvent from this electrolyte solution. This process occurs widely in nature, and is the means of formation of the evaporite minerals, insoluble ionic compounds can be precipitated by mixing two solutions, one with the cation and one with the anion in it. Because all solutions are neutral, the two solutions mixed must also contain counterions of the opposite charges. To ensure that these do not contaminate the precipitated ionic compound, if the two solutions have hydrogen ions and hydroxide ions as the counterions, they will react with one another in what is called an acid–base reaction or a neutralization reaction to form water. Alternately the counterions can be chosen to ensure that even when combined into a solution they will remain soluble as spectator ions. Molten salts will solidify on cooling to below their freezing point and this is sometimes used for the solid-state synthesis of complex ionic compounds from solid reactants, which are first melted together. In other cases the solid reactants do not need to be melted, other synthetic routes use a solid precursor with the correct stoichiometric ratio of non-volatile ions, which is heated to drive off other species. There is also an additional attractive force from van der Waals interactions which contributes only around 1–2% of the cohesive energy for small ions
3.
Alkaline earth metal
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The alkaline earth metals are six chemical elements in column 2 of the Periodic table. They are beryllium, magnesium, calcium, strontium, barium, the elements have very similar properties, they are all shiny, silvery-white, somewhat reactive metals at standard temperature and pressure. All the discovered alkaline earth metals occur in nature, experiments have been conducted to attempt the synthesis of element 120, the next potential member of the group, but they have all met with failure. The chemistry of radium is not well-established due to its radioactivity, thus, the alkaline earth metals are all silver-colored and soft, and have relatively low densities, melting points, and boiling points. In chemical terms, all of the alkaline metals react with the halogens to form the earth metal halides. All the alkaline earth metals except beryllium also react with water to form strongly alkaline hydroxides and, thus, the heavier alkaline earth metals react more vigorously than the lighter ones. The second ionization energy of all of the metals is also somewhat low. Beryllium is an exception, It does not react with water or steam, all compounds that include beryllium have a covalent bond. Even the compound beryllium fluoride, which is the most ionic beryllium compound, has a low melting point and a low electrical conductivity when melted. The alkaline earth metals all react with the halogens to form ionic halides, such as calcium chloride, calcium, strontium, and barium react with water to produce hydrogen gas and their respective hydroxides, and also undergo transmetalation reactions to exchange ligands. The table below is a summary of the key physical and atomic properties of the alkaline earth metals, calcium-48 is the lightest nuclide to undergo double beta decay. The natural radioisotope of calcium, calcium-48, makes up about 0. 1874% of natural calcium, barium-130 makes up approximately 0. 1062% of natural barium, and, thus, barium is weakly radioactive, as well. The alkaline earth metals are named after their oxides, the alkaline earths, whose old-fashioned names were beryllia, magnesia, lime, strontia and these oxides are basic when combined with water. Earth is an old term applied by early chemists to nonmetallic substances that are insoluble in water, the realization that these earths were not elements but compounds is attributed to the chemist Antoine Lavoisier. In his Traité Élémentaire de Chimie of 1789 he called them salt-forming earth elements, later, he suggested that the alkaline earths might be metal oxides, but admitted that this was mere conjecture. The calcium compounds calcite and lime have been known and used since prehistoric times, the same is true for the beryllium compounds beryl and emerald. The other compounds of the alkaline earth metals were discovered starting in the early 15th century, the magnesium compound magnesium sulfate was first discovered in 1618 by a farmer at Epsom in England. Strontium carbonate was discovered in minerals in the Scottish village of Strontian in 1790, the last element is the least abundant, radioactive radium, which was extracted from uraninite in 1898
4.
Chemical element
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A chemical element or element is a species of atoms having the same number of protons in their atomic nuclei. There are 118 elements that have identified, of which the first 94 occur naturally on Earth with the remaining 24 being synthetic elements. There are 80 elements that have at least one stable isotope and 38 that have exclusively radioactive isotopes, iron is the most abundant element making up Earth, while oxygen is the most common element in the Earths crust. Chemical elements constitute all of the matter of the universe. The two lightest elements, hydrogen and helium, were formed in the Big Bang and are the most common elements in the universe. The next three elements were formed mostly by cosmic ray spallation, and are rarer than those that follow. Formation of elements with from 6 to 26 protons occurred and continues to occur in main sequence stars via stellar nucleosynthesis, the high abundance of oxygen, silicon, and iron on Earth reflects their common production in such stars. The term element is used for atoms with a number of protons as well as for a pure chemical substance consisting of a single element. A single element can form multiple substances differing in their structure, when different elements are chemically combined, with the atoms held together by chemical bonds, they form chemical compounds. Only a minority of elements are found uncombined as relatively pure minerals, among the more common of such native elements are copper, silver, gold, carbon, and sulfur. All but a few of the most inert elements, such as gases and noble metals, are usually found on Earth in chemically combined form. While about 32 of the elements occur on Earth in native uncombined forms. For example, atmospheric air is primarily a mixture of nitrogen, oxygen, and argon, the history of the discovery and use of the elements began with primitive human societies that found native elements like carbon, sulfur, copper and gold. Later civilizations extracted elemental copper, tin, lead and iron from their ores by smelting, using charcoal, alchemists and chemists subsequently identified many more, almost all of the naturally occurring elements were known by 1900. Save for unstable radioactive elements with short half-lives, all of the elements are available industrially, almost all other elements found in nature were made by various natural methods of nucleosynthesis. On Earth, small amounts of new atoms are produced in nucleogenic reactions, or in cosmogenic processes. Of the 94 naturally occurring elements, those with atomic numbers 1 through 82 each have at least one stable isotope, Isotopes considered stable are those for which no radioactive decay has yet been observed. Elements with atomic numbers 83 through 94 are unstable to the point that radioactive decay of all isotopes can be detected, the very heaviest elements undergo radioactive decay with half-lives so short that they are not found in nature and must be synthesized
5.
Water
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Water is a transparent and nearly colorless chemical substance that is the main constituent of Earths streams, lakes, and oceans, and the fluids of most living organisms. Its chemical formula is H2O, meaning that its molecule contains one oxygen, Water strictly refers to the liquid state of that substance, that prevails at standard ambient temperature and pressure, but it often refers also to its solid state or its gaseous state. It also occurs in nature as snow, glaciers, ice packs and icebergs, clouds, fog, dew, aquifers, Water covers 71% of the Earths surface. It is vital for all forms of life. Only 2. 5% of this water is freshwater, and 98. 8% of that water is in ice and groundwater. Less than 0. 3% of all freshwater is in rivers, lakes, and the atmosphere, a greater quantity of water is found in the earths interior. Water on Earth moves continually through the cycle of evaporation and transpiration, condensation, precipitation. Evaporation and transpiration contribute to the precipitation over land, large amounts of water are also chemically combined or adsorbed in hydrated minerals. Safe drinking water is essential to humans and other even though it provides no calories or organic nutrients. There is a correlation between access to safe water and gross domestic product per capita. However, some observers have estimated that by 2025 more than half of the population will be facing water-based vulnerability. A report, issued in November 2009, suggests that by 2030, in developing regions of the world. Water plays an important role in the world economy, approximately 70% of the freshwater used by humans goes to agriculture. Fishing in salt and fresh water bodies is a source of food for many parts of the world. Much of long-distance trade of commodities and manufactured products is transported by boats through seas, rivers, lakes, large quantities of water, ice, and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a variety of chemical substances, as such it is widely used in industrial processes. Water is also central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, surfing, sport fishing, Water is a liquid at the temperatures and pressures that are most adequate for life. Specifically, at atmospheric pressure of 1 bar, water is a liquid between the temperatures of 273.15 K and 373.15 K
6.
PH
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In chemistry, pH is a numeric scale used to specify the acidity or basicity of an aqueous solution. It is approximately the negative of the base 10 logarithm of the concentration, measured in units of moles per liter. More precisely it is the negative of the logarithm to base 10 of the activity of the hydrogen ion, solutions with a pH less than 7 are acidic and solutions with a pH greater than 7 are basic. Pure water is neutral, at pH7, being neither an acid nor a base, contrary to popular belief, the pH value can be less than 0 or greater than 14 for very strong acids and bases respectively. The pH scale is traceable to a set of standard solutions whose pH is established by international agreement, the pH of aqueous solutions can be measured with a glass electrode and a pH meter, or an indicator. In the first papers, the notation had the H as a subscript to the p, as so. The exact meaning of the p in pH is disputed, but according to the Carlsberg Foundation and it has also been suggested that the p stands for the German Potenz, others refer to French puissance. Another suggestion is that the p stands for the Latin terms pondus hydrogenii, potentia hydrogenii and it is also suggested that Sørensen used the letters p and q simply to label the test solution and the reference solution. Currently in chemistry, the p stands for decimal cologarithm of, PH is defined as the decimal logarithm of the reciprocal of the hydrogen ion activity, aH+, in a solution. P H = − log 10 = log 10 For example and this definition was adopted because ion-selective electrodes, which are used to measure pH, respond to activity. For H+ number of electrons transferred is one and it follows that electrode potential is proportional to pH when pH is defined in terms of activity. The reference electrode may be a silver chloride electrode or a calomel electrode, the hydrogen-ion selective electrode is a standard hydrogen electrode. Reference electrode | concentrated solution of KCl || test solution | H2 | Pt Firstly, the cell is filled with a solution of hydrogen ion activity. Then the emf, EX, of the cell containing the solution of unknown pH is measured. PH = pH + E S − E X z The difference between the two measured emf values is proportional to pH and this method of calibration avoids the need to know the standard electrode potential. The proportionality constant, 1/z is ideally equal to 12.303 R T / F the Nernstian slope, to apply this process in practice, a glass electrode is used rather than the cumbersome hydrogen electrode. A combined glass electrode has a reference electrode. It is calibrated against buffer solutions of hydrogen ion activity
7.
Chemical engineering
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A chemical engineer designs large-scale processes that convert chemicals, raw materials, living cells, microorganisms and energy into useful forms and products. A1996 British Journal for the History of Science article cites James F. Donnelly for mentioning an 1839 reference to chemical engineering in relation to the production of sulfuric acid. In the same however, George E. Davis, an English consultant, was credited for having coined the term. The History of Science in United States, An Encyclopedia puts this at around 1890, Chemical engineering, describing the use of mechanical equipment in the chemical industry, became common vocabulary in England after 1850. By 1910, the profession, chemical engineer, was already in use in Britain. Chemical engineering emerged upon the development of operations, a fundamental concept of the discipline of chemical engineering. Most authors agree that Davis invented the concept of operations if not substantially developed it. He gave a series of lectures on unit operations at the Manchester Technical School in 1887, three years before Davis lectures, Henry Edward Armstrong taught a degree course in chemical engineering at the City and Guilds of London Institute. Armstrongs course failed simply because its graduates, were not especially attractive to employers. Employers of the time would have rather hired chemists and mechanical engineers, starting from 1888, Lewis M. Norton taught at MIT the first chemical engineering course in the United States. Nortons course was contemporaneous and essentially similar with Armstrongs course, both courses, however, simply merged chemistry and engineering subjects. Its practitioners had difficulty convincing engineers that they were engineers and chemists that they were not simply chemists, unit operations was introduced into the course by William Hultz Walker in 1905. By the early 1920s, unit operations became an important aspect of engineering at MIT and other US universities. For instance, it defined chemical engineering to be a science of itself, unit operations in a 1922 report, and with which principle, it had published a list of academic institutions which offered satisfactory chemical engineering courses. Meanwhile, promoting chemical engineering as a science in Britain lead to the establishment of the Institution of Chemical Engineers in 1922. IChemE likewise helped make unit operations considered essential to the discipline, by the 1940s, it became clear that unit operations alone was insufficient in developing chemical reactors. While the predominance of unit operations in chemical engineering courses in Britain, along with other novel concepts, such process systems engineering, a second paradigm was defined. Transport phenomena gave an analytical approach to chemical engineering while PSE focused on its elements, such as control system
8.
Cabbage
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Cabbage or headed cabbage is a leafy green or purple biennial plant, grown as an annual vegetable crop for its dense-leaved heads. It is descended from the cabbage, B. oleracea var. oleracea. Cabbage heads generally range from 0.5 to 4 kilograms, smooth-leafed firm-headed green cabbages are the most common, with smooth-leafed red and crinkle-leafed savoy cabbages of both colors seen more rarely. Under conditions of long sunlit days such as are found at high latitudes in summer. Some records are discussed at the end of the history section and it is difficult to trace the exact history of cabbage, but it was most likely domesticated somewhere in Europe before 1000 BC, although savoys were not developed until the 16th century. By the Middle Ages, it had become a prominent part of European cuisine, cabbage is prone to several nutrient deficiencies, as well as to multiple pests, and bacterial and fungal diseases. The Food and Agriculture Organization of the United Nations reports that production of cabbage. Almost half of these crops were grown in China, where Chinese cabbage is the most popular Brassica vegetable, cabbages are prepared in many different ways for eating. They can be pickled, fermented for dishes such as sauerkraut, steamed, stewed, sautéed, braised, cabbage is a good source of vitamin K, vitamin C and dietary fiber. Contaminated cabbage has been linked to cases of illness in humans. Cabbage is a member of the genus Brassica and the mustard family, several other cruciferous vegetables are considered cultivars of B. oleracea, including broccoli, collard greens, brussels sprouts, kohlrabi and sprouting broccoli. All of these developed from the wild cabbage B. oleracea var. oleracea, the varietal epithet capitata is derived from the Latin word for having a head. B. oleracea and its derivatives have hundreds of names throughout the world. Cabbage was originally used to refer to forms of B. oleracea. A related species, Brassica rapa, is commonly named Chinese, napa or celery cabbage and it is also a part of common names for several unrelated species. These include cabbage bark or cabbage tree and cabbage palms, which include several genera of palms such as Mauritia, Roystonea oleracea, Acrocomia, the original family name of brassicas was Cruciferae, which derived from the flower petal pattern thought by medieval Europeans to resemble a crucifix. The word brassica derives from bresic, a Celtic word for cabbage, many European and Asiatic names for cabbage are derived from the Celto-Slavic root cap or kap, meaning head. The late Middle English word cabbage derives from the word caboche and this in turn is a variant of the Old French caboce
9.
Soda lake
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A soda lake or alkaline lake is a lake on the strongly alkaline side of neutrality. They are characterized by high concentrations of salts, typically sodium carbonate. In addition, many lakes also contain high concentrations of sodium chloride and other dissolved salts. High pH and salinity often coincide, because of how soda lakes develop, the resulting hypersaline and highly alkalic soda lakes are considered some of the most extreme aquatic environments on Earth. In spite of their apparent inhospitability, soda lakes are often highly productive ecosystems, gross primary production rates above 10 g C m−2 day−1, over 16 times the global average for lakes and streams, have been measured. This makes them the most productive aquatic environments on Earth, an important reason for the high productivity is the virtually unlimited availability of dissolved carbon dioxide. Soda lakes occur naturally throughout the world, typically in arid and semi-arid areas, the pH of most freshwater lakes is on the alkaline side of neutrality and many exhibit similar water chemistries to soda lakes, only less extreme. In order for a lake to become alkalic, a combination of geographic, geological. First of all, a suitable topography is needed, that limits the outflow of water from the lake, when the outflow is completely prevented, this is called an endorheic basin. Craters or depressions formed by tectonic rifting often provide such topological depressions, the high alkalinity and salinity arise through evaporation of the lake water. This requires suitable conditions, in order for the inflow to balance outflow through evaporation. Another critical geological condition for the formation of a lake is the relative absence of soluble magnesium or calcium. This results in a salt lake instead. A good example is the Dead Sea, which is rich in Mg2+. In some soda lakes, inflow of Ca2+ through subterranean seeps, in Mono Lake, California and Lake Van, Turkey, such precipitation has formed columns of tufa rising above the lake surface. Many soda lakes are strongly stratified, with well-oxygenated upper layer, stratification can be permanent, or with seasonal mixing. The depth of the interface separating the two layers varies from a few centimeters to near the bottom sediments, depending on local conditions. In either case, it represents an important barrier, both physically and between strongly contrasting biochemical conditions, a rich diversity of microbial life inhabit soda lakes, often in dense concentrations
