1.
Chemistry
–
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.
Louis Pasteur
–
Louis Pasteur was a French biologist, microbiologist and chemist renowned for his discoveries of the principles of vaccination, microbial fermentation and pasteurization. He is remembered for his breakthroughs in the causes and prevention of diseases. He reduced mortality from puerperal fever, and created the first vaccines for rabies and his medical discoveries provided direct support for the germ theory of disease and its application in clinical medicine. He is best known to the public for his invention of the technique of treating milk and wine to stop bacterial contamination. He is regarded as one of the three founders of bacteriology, together with Ferdinand Cohn and Robert Koch, and is popularly known as the father of microbiology. Pasteur was responsible for disproving the doctrine of spontaneous generation and he performed experiments that showed that without contamination, microorganisms could not develop. Under the auspices of the French Academy of Sciences, he demonstrated that in sterilized and sealed flasks nothing ever developed, although Pasteur was not the first to propose the germ theory, his experiments indicated its correctness and convinced most of Europe that it was true. Today, he is regarded as one of the fathers of germ theory. Pasteur also made significant discoveries in chemistry, most notably on the basis for the asymmetry of certain crystals. Early in his career, his investigation of tartaric acid resulted in the first resolution of what is now called optical isomers and his work led the way to the current understanding of a fundamental principle in the structure of organic compounds. He was the director of the Pasteur Institute, established in 1887, till his death, although Pasteur made groundbreaking experiments, his reputation became associated with various controversies. Historical reassessment of his notebook revealed that he practiced deception to overcome his rivals, Louis Pasteur was born on December 27,1822, in Dole, Jura, France, to a Catholic family of a poor tanner. He was the child of Jean-Joseph Pasteur and Jeanne-Etiennette Roqui. The family moved to Marnoz in 1826 and then to Arbois in 1827, Pasteur entered primary school in 1831. He was a student in his early years, and not particularly academic. He drew many pastels and portraits of his parents, friends, Pasteur attended secondary school at the Collège dArbois. In October 1838, he left for Paris to join the Pension Barbet, in 1839, he entered the Collège Royal de Besançon to study philosophy and earned his Bachelor of Letters degree in 1840. He was appointed a tutor at the Besançon college while continuing a degree course with special mathematics
3.
Polarization (waves)
–
Polarization is a parameter applying to transverse waves that specifies the geometrical orientation of the oscillations. In a transverse wave the direction of the oscillation is transverse to the direction of motion of the wave, a simple example of a polarized transverse wave is vibrations traveling along a taut string for example in a musical instrument like a guitar string. Depending on how the string is plucked, the vibrations can be in a direction, horizontal direction. Transverse waves that exhibit polarization include electromagnetic waves such as light and radio waves, gravitational waves, in some types of transverse waves the wave displacement is limited to a single direction, so these also dont exhibit polarization. For example, in waves in liquids the wave displacement of the particles is always in a vertical plane. In linear polarization the fields oscillate in a single direction, in circular or elliptical polarization the fields rotate at a constant rate in a plane as the wave travels. Polarized light can be produced by passing unpolarized light through a polarizing filter, some of these are used to make polarizing filters. Light is also partially polarized when it reflects from a surface, according to quantum mechanics, electromagnetic waves consist of particles called photons. When viewed in this way, the polarization of a wave is determined by a quantum mechanical property of photons called their spin. A photon has one of two spins, it can either spin in a right hand sense or a left hand sense about its direction of travel. Circularly polarized electromagnetic waves are composed of photons with one type of spin. Linearly polarized waves consist of numbers of right and left hand spinning photons. Polarization is an important parameter in areas of science dealing with transverse waves, such as optics, seismology, radio, especially impacted are technologies such as lasers, wireless and optical fiber telecommunications, and radar. And incoherent states can be modeled stochastically as a combination of such uncorrelated waves with some distribution of frequencies, phases. Considering a monochromatic wave of optical frequency f, let us take the direction of propagation as the z axis. Being a transverse wave the E and H fields must then contain components only in the x and y directions whereas Ez=Hz=0. Using complex notation, we understand the instantaneous electric and magnetic fields to be given by the real parts of the complex quantities occurring in the following equations. Here ex, ey, hx, and hy are complex numbers, in the second more compact form, as these equations are customarily expressed, these factors are described using the wavenumber k =2 π n / λ and angular frequency ω =2 π f
4.
Methamphetamine
–
Methamphetamine is a strong central nervous system stimulant that is mainly used as a recreational drug and less commonly as a treatment for attention deficit hyperactivity disorder and obesity. Methamphetamine was discovered in 1893 and exists as two enantiomers, levo-methamphetamine and dextro-methamphetamine, Methamphetamine properly refers to a specific chemical, the racemic free base, which is an equal mixture of levomethamphetamine and dextromethamphetamine in their pure amine forms. Dextromethamphetamine is a much stronger CNS stimulant than levomethamphetamine, both methamphetamine and dextromethamphetamine are illicitly trafficked and sold owing to their potential for recreational use. Levomethamphetamine is available as a drug for use as an inhaled nasal decongestant in the United States. While dextromethamphetamine is a potent drug, racemic methamphetamine is sometimes illicitly produced due to the relative ease of synthesis. In low doses, methamphetamine can elevate mood, increase alertness, concentration and energy in fatigued individuals, at higher doses, it can induce psychosis, breakdown of skeletal muscle, seizures and bleeding in the brain. Chronic high-dose use can precipitate unpredictable and rapid mood swings, prominent delusions, Methamphetamine is known to have a high addiction liability and dependence liability. Heavy recreational use of methamphetamine may lead to a post-acute-withdrawal syndrome, unlike amphetamine, methamphetamine is neurotoxic to human midbrain dopaminergic neurons. It has also shown to damage serotonin neurons in the CNS. This damage includes adverse changes in structure and function, such as reductions in grey matter volume in several brain regions. Methamphetamine belongs to the phenethylamine and substituted amphetamine chemical classes. It is related to the other dimethylphenethylamines as an isomer of these compounds. Methamphetamine is sometimes prescribed off label for narcolepsy and idiopathic hypersomnia, in the United States, methamphetamines levorotary form is available in some over-the-counter nasal decongestant products. As methamphetamine is associated with a potential for misuse, the drug is regulated under the Controlled Substances Act and is listed under schedule II in the United States. Methamphetamine hydrochloride dispensed in the United States is required to include a warning regarding its potential for recreational misuse. Methamphetamine is often used recreationally for its effects as a potent euphoriant and stimulant as well as aphrodisiac qualities, according to a National Geographic TV documentary on methamphetamine, an entire subculture known as party and play is based around methamphetamine use. Members of this San Francisco sub-culture, which consists almost entirely of gay male methamphetamine users, due to its strong stimulant and aphrodisiac effects and inhibitory effect on ejaculation, with repeated use, these sexual encounters will sometimes occur continuously for several days on end. The crash following the use of methamphetamine in this manner is often severe
5.
Melting point
–
The melting point of a solid is the temperature at which it changes state from solid to liquid at atmospheric pressure. At the melting point the solid and liquid phase exist in equilibrium, the melting point of a substance depends on pressure and is usually specified at standard pressure. When considered as the temperature of the change from liquid to solid. Because of the ability of some substances to supercool, the point is not considered as a characteristic property of a substance. For most substances, melting and freezing points are approximately equal, for example, the melting point and freezing point of mercury is 234.32 kelvins. However, certain substances possess differing solid-liquid transition temperatures, for example, agar melts at 85 °C and solidifies from 31 °C to 40 °C, such direction dependence is known as hysteresis. The melting point of ice at 1 atmosphere of pressure is close to 0 °C. In the presence of nucleating substances the freezing point of water is the same as the melting point, the chemical element with the highest melting point is tungsten, at 3687 K, this property makes tungsten excellent for use as filaments in light bulbs. Many laboratory techniques exist for the determination of melting points, a Kofler bench is a metal strip with a temperature gradient. Any substance can be placed on a section of the strip revealing its thermal behaviour at the temperature at that point, differential scanning calorimetry gives information on melting point together with its enthalpy of fusion. A basic melting point apparatus for the analysis of crystalline solids consists of an oil bath with a transparent window, the several grains of a solid are placed in a thin glass tube and partially immersed in the oil bath. The oil bath is heated and with the aid of the melting of the individual crystals at a certain temperature can be observed. In large/small devices, the sample is placed in a heating block, the measurement can also be made continuously with an operating process. For instance, oil refineries measure the point of diesel fuel online, meaning that the sample is taken from the process. This allows for more frequent measurements as the sample does not have to be manually collected, for refractory materials the extremely high melting point may be determined by heating the material in a black body furnace and measuring the black-body temperature with an optical pyrometer. For the highest melting materials, this may require extrapolation by several hundred degrees, the spectral radiance from an incandescent body is known to be a function of its temperature. An optical pyrometer matches the radiance of a body under study to the radiance of a source that has been previously calibrated as a function of temperature, in this way, the measurement of the absolute magnitude of the intensity of radiation is unnecessary. However, known temperatures must be used to determine the calibration of the pyrometer, for temperatures above the calibration range of the source, an extrapolation technique must be employed
6.
Dumbbell
–
The dumbbell, a type of free weight, is a piece of equipment used in weight training. It can be used individually or in pairs, with one in each hand, the forerunner of the dumbbell, halteres, were used in ancient Greece as lifting weights and also as weights in the ancient Greek version of the long jump. A kind of dumbbell was also used in India for more than a millennium, despite their common English name implying an Indian origin, the so-called Indian clubs were in fact created in the Near East. Properly referred to as meels, they are first recorded as being used by wrestlers in ancient Persia, Egypt, the practice has continued to the present day, notably in the Varzesh-e Bastan tradition practiced in the zurkaneh of Iran. From Persia, the Mughals brought the meels to South Asia where are still used by pehlwan, british colonists first came across Persian meels in India, and erroneously referred to them as Indian clubs despite their Middle Eastern origin. The design of the Nal, as the equipment was referred to and it was generally used in pairs, in workouts by wrestlers, bodybuilders, sports players, and others wishing to increase strength and muscle size. The term dumbbell or dumb bell originated in late Stuart England, in 1711 the poet Joseph Addison mentioned exercising with a dumb bell in an essay published in The Spectator. By the early 17th century, the shape of the dumbbell. There are currently three main types of dumbbell, Adjustable dumbbells consist of a metal bar whose centre portion is engraved with a crosshatch pattern to improve grip. Weight plates are slid onto the outer portions of the dumbbell, shown to the right is a spinlock dumbbell, whose ends are threaded to accept large nuts as collars. Alternatively, a dumbbell may have smooth ends with plates being secured by a sprung collar, nowadays, many commercially sold dumbbells are available with sophisticated, and easy-to-use methods for weight increments adjustments. Fixed-weight dumbbells are weights created in a dumbbell shape, inexpensive varieties consist of cast iron, sometimes coated with rubber or neoprene for comfort, and even cheaper versions consist of a rigid plastic shell that is filled with concrete. Selectorized dumbbells are adjustable dumbbells whose number of plates can be changed when resting in the dumbbell stand. This is achieved by adjusting the number of plates that follow the handle when lifted and this makes it very easy to change the weight of the dumbbell between exercises, and the stand typically doubles as storage for the additional weights not being used for a particular exercise. Barbell Kettlebell Weights Weight lifting belt Pool dumbbell Bulgarian Bag Media related to Dumbbells at Wikimedia Commons Guide to different types of dumbbell
7.
Chromatography
–
Chromatography is a laboratory technique for the separation of a mixture. The mixture is dissolved in a called the mobile phase. The various constituents of the mixture travel at different speeds, causing them to separate, the separation is based on differential partitioning between the mobile and stationary phases. Subtle differences in a partition coefficient result in differential retention on the stationary phase. Chromatography may be preparative or analytical, the purpose of preparative chromatography is to separate the components of a mixture for later use, and is thus a form of purification. Analytical chromatography is done normally with smaller amounts of material and is for establishing the presence or measuring the proportions of analytes in a mixture. The two are not mutually exclusive, Chromatography was first employed in Russia by the Italian-born scientist Mikhail Tsvet in 1900. He continued to work with chromatography in the first decade of the 20th century, primarily for the separation of plant pigments such as chlorophyll, carotenes, since these components have different colors they gave the technique its name. New types of chromatography developed during the 1930s and 1940s made the technique useful for separation processes. Since then, the technology has advanced rapidly, researchers found that the main principles of Tsvets chromatography could be applied in many different ways, resulting in the different varieties of chromatography described below. Advances are continually improving the performance of chromatography, allowing the separation of increasingly similar molecules. The analyte is the substance to be separated during chromatography and it is also normally what is needed from the mixture. Analytical chromatography is used to determine the existence and possibly also the concentration of analyte in a sample, a bonded phase is a stationary phase that is covalently bonded to the support particles or to the inside wall of the column tubing. A chromatogram is the output of the chromatograph. In the case of a separation, different peaks or patterns on the chromatogram correspond to different components of the separated mixture. Plotted on the x-axis is the time and plotted on the y-axis a signal corresponding to the response created by the analytes exiting the system. In the case of a system the signal is proportional to the concentration of the specific analyte separated. A chromatograph is equipment that enables a sophisticated separation, e. g. gas chromatographic or liquid chromatographic separation, Chromatography is a physical method of separation that distributes components to separate between two phases, one stationary, the other moving in a definite direction
8.
Catalysis
–
Catalysis is the increase in the rate of a chemical reaction due to the participation of an additional substance called a catalyst. In most cases, reactions occur faster with a catalyst because they require less activation energy, furthermore, since they are not consumed in the catalyzed reaction, catalysts can continue to act repeatedly. Often only tiny amounts are required in principle, in the presence of a catalyst, less free energy is required to reach the transition state, but the total free energy from reactants to products does not change. A catalyst may participate in multiple chemical transformations, the effect of a catalyst may vary due to the presence of other substances known as inhibitors or poisons or promoters. Catalyzed reactions have an activation energy than the corresponding uncatalyzed reaction, resulting in a higher reaction rate at the same temperature. However, the mechanics of catalysis is complex. Usually, the catalyst participates in this slowest step, and rates are limited by amount of catalyst, in heterogeneous catalysis, the diffusion of reagents to the surface and diffusion of products from the surface can be rate determining. A nanomaterial-based catalyst is an example of a heterogeneous catalyst, analogous events associated with substrate binding and product dissociation apply to homogeneous catalysts. Although catalysts are not consumed by the reaction itself, they may be inhibited, deactivated, in heterogeneous catalysis, typical secondary processes include coking where the catalyst becomes covered by polymeric side products. Additionally, heterogeneous catalysts can dissolve into the solution in a system or sublimate in a solid–gas system. The production of most industrially important chemicals involves catalysis, similarly, most biochemically significant processes are catalysed. Research into catalysis is a field in applied science and involves many areas of chemistry, notably organometallic chemistry. Catalysis is relevant to aspects of environmental science, e. g. the catalytic converter in automobiles. Many transition metals and transition metal complexes are used in catalysis as well, Catalysts called enzymes are important in biology. A catalyst works by providing a reaction pathway to the reaction product. The rate of the reaction is increased as this route has a lower activation energy than the reaction route not mediated by the catalyst. The disproportionation of hydrogen peroxide creates water and oxygen, as shown below,2 H2O2 →2 H2O + O2 This reaction is preferable in the sense that the reaction products are more stable than the starting material, though the uncatalysed reaction is slow. In fact, the decomposition of hydrogen peroxide is so slow that hydrogen peroxide solutions are commercially available and this reaction is strongly affected by catalysts such as manganese dioxide, or the enzyme peroxidase in organisms
9.
Carbocation
–
A carbocation is an ion with a positively charged carbon atom. Among the simplest examples are methenium CH+3, methanium CH+5, some carbocations may have two or more positive charges, on the same carbon atom or on different atoms, such as the ethylene dication C 2H2+4. Until the early 1970s, all carbocations were called carbonium ions and this nomenclature was proposed by G. A. Olah. One textbook retains the name of carbonium ion for carbenium ion to this day. The history of carbocations dates back to 1891 when G. Merling reported that he added bromine to tropylidene and then heated the product to obtain a crystalline, water-soluble material, C 7H 7Br. He did not suggest a structure for it, however, Doering and this ion is predicted to be aromatic by Hückels rule. In 1902, Norris and Kehrman independently discovered that colorless triphenylmethanol gives deep-yellow solutions in concentrated sulfuric acid, triphenylmethyl chloride similarly formed orange complexes with aluminium and tin chlorides. In 1902, Adolf von Baeyer recognized the character of the compounds formed. He dubbed the relationship between color and salt formation halochromy, of which green is a prime example. Carbocations are reactive intermediates in organic reactions. This idea, first proposed by Julius Stieglitz in 1899, was developed by Hans Meerwein in his 1922 study of the Wagner–Meerwein rearrangement. Carbocations were also found to be involved in the SN1 reaction, the E1 reaction, the chemical establishment was reluctant to accept the notion of a carbocation and for a long time the Journal of the American Chemical Society refused articles that mentioned them. The first NMR spectrum of a carbocation in solution was published by Doering et al. in 1958. It was the ion, made by treating hexamethylbenzene with methyl chloride. The stable 7-norbornadienyl cation was prepared by Story et al. in 1960 by reacting norbornadienyl chloride with silver tetrafluoroborate in sulfur dioxide at −80 °C, the NMR spectrum established that it was non-classically bridged. In 1962, Olah directly observed the tert-butyl carbocation by nuclear magnetic resonance as a species on dissolving tert-butyl fluoride in magic acid. The NMR of the norbornyl cation was first reported by Schleyer et al. the charged carbon atom in a carbocation is a sextet, i. e. it has only six electrons in its outer valence shell instead of the eight valence electrons that ensures maximum stability. Therefore, carbocations are often reactive, seeking to fill the octet of electrons as well as regain a neutral charge
10.
Otto Wallach
–
Otto Wallach was a German chemist and recipient of the 1910 Nobel Prize in Chemistry for his work on alicyclic compounds. Wallach was born in Königsberg, the son of a Prussian civil servant and his father, Gerhard Wallach, descended from a Jewish family that had converted to Lutheranism. His mother, Otillie, was an ethnic German of Protestant religion, Wallachs father was transferred to Stettin and later to Potsdam. Otto Wallach went to school, a Gymnasium, in Potsdam, where he learned about literature, at this time he also started private chemical experiments at the house of his parents. In 1867 he started studying chemistry at the University of Göttingen, during his work with Friedrich Kekulé in Bonn he started a systematic analysis of the terpenes present in essential oils. Up to this only a few had been isolated in pure form. Melting point comparison and the measurement of mixtures was one of the methods to confirm identical substances, for this method the mostly liquid terpenes had to be transformed into crystalline compounds. With stepwise derivatisation, especially additions to the double bond present in some of the terpenes, with these principal methods he opened the path to systematic research on terpenes. He was responsible for naming terpene and pinene, and for undertaking the first systematic study of pinene^ and he wrote a book about the chemistry of terpenes, Terpene und Campher. Otto Wallach is known for Wallachs rule, Wallach degradation, the Leuckart-Wallach reaction, digital edition of the University and State Library Düsseldorf. Verhalten der Elemente und ihrer Verbindungen, methoden zur Auffindung und Trennung der Elemente. Aufl. von Hülfstabellen für den chemisch-analytischen Unterricht 1880 Terpene und Campher, digital edition of the University and State Library Düsseldorf. Nobel Lecture Alicyclic Compounds from Nobelprize. org website Biography Biography from Nobelprize. org website Otto Wallach at the NNDB website
11.
Boiling point
–
The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the environmental pressure. A liquid in a vacuum has a lower boiling point than when that liquid is at atmospheric pressure. A liquid at high pressure has a boiling point than when that liquid is at atmospheric pressure. For a given pressure, different liquids boil at different temperatures, for example, water boils at 100 °C at sea level, but at 93.4 °C at 2,000 metres altitude. The normal boiling point of a liquid is the case in which the vapor pressure of the liquid equals the defined atmospheric pressure at sea level,1 atmosphere. At that temperature, the pressure of the liquid becomes sufficient to overcome atmospheric pressure. The standard boiling point has been defined by IUPAC since 1982 as the temperature at which boiling occurs under a pressure of 1 bar, the heat of vaporization is the energy required to transform a given quantity of a substance from a liquid into a gas at a given pressure. Liquids may change to a vapor at temperatures below their boiling points through the process of evaporation, evaporation is a surface phenomenon in which molecules located near the liquids edge, not contained by enough liquid pressure on that side, escape into the surroundings as vapor. On the other hand, boiling is a process in which molecules anywhere in the liquid escape, a saturated liquid contains as much thermal energy as it can without boiling. The saturation temperature is the temperature for a corresponding saturation pressure at which a liquid boils into its vapor phase, the liquid can be said to be saturated with thermal energy. Any addition of energy results in a phase transition. If the pressure in a system remains constant, a vapor at saturation temperature will begin to condense into its liquid phase as thermal energy is removed, similarly, a liquid at saturation temperature and pressure will boil into its vapor phase as additional thermal energy is applied. The boiling point corresponds to the temperature at which the pressure of the liquid equals the surrounding environmental pressure. Thus, the point is dependent on the pressure. Boiling points may be published with respect to the NIST, USA standard pressure of 101.325 kPa, at higher elevations, where the atmospheric pressure is much lower, the boiling point is also lower. The boiling point increases with increased pressure up to the critical point, the boiling point cannot be increased beyond the critical point. Likewise, the point decreases with decreasing pressure until the triple point is reached
