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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
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Physical model
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Physical model is a smaller or larger physical copy of an object. The object being modelled may be small or large, the geometry of the model and the object it represents are often similar in the sense that one is a rescaling of the other, in such cases the scale is an important characteristic. However, in cases the similarity is only approximate or even intentionally distorted. Sometimes the distortion is systematic with e. g. a fixed scale horizontally, physical models allow visualization, from examining the model, of information about the thing the model represents. A model can be an object such as an architectural model of a building. Uses of a model include visualization of internal relationships within the structure or external relationships of the structure to the environment. Other uses of models in this sense are as toys, instrumented physical models are the most effective way of investigating fluid flows such as around hydraulic structures. These models are scaled in terms of geometry and important forces, for example using Froude number or Reynolds number scaling. A physical model of something large is usually smaller, and of something very small is larger, a physical model of something that can move, like a vehicle or machine, may be completely static, or have parts that can be moved manually, or be powered. A physical model may show inner parts that are not visible. The purpose of a model on a smaller scale may be to have a better overview, for testing purposes. A physical model of an animal shows the physical composition without it walking or flying away, and without danger. A soft model of an animal is popular among children and some adults as cuddly toy. some models can be used in different ways as of like prototypes for cars. A model of a person may e. g. be a doll, a statue, and in fiction a robotic humanoid, e. g. the mechas in the movie A. I. A model is a 3D alternative for a 2D representation such as a drawing or photograph, or in the case of a globe, scale model Mathematical model Model organism Model nation Metamodeling Model airplane Model car Model railway Model rocket Model house
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Computer
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A computer is a device that can be instructed to carry out an arbitrary set of arithmetic or logical operations automatically. The ability of computers to follow a sequence of operations, called a program, such computers are used as control systems for a very wide variety of industrial and consumer devices. The Internet is run on computers and it millions of other computers. Since ancient times, simple manual devices like the abacus aided people in doing calculations, early in the Industrial Revolution, some mechanical devices were built to automate long tedious tasks, such as guiding patterns for looms. More sophisticated electrical machines did specialized analog calculations in the early 20th century, the first digital electronic calculating machines were developed during World War II. The speed, power, and versatility of computers has increased continuously and dramatically since then, conventionally, a modern computer consists of at least one processing element, typically a central processing unit, and some form of memory. The processing element carries out arithmetic and logical operations, and a sequencing, peripheral devices include input devices, output devices, and input/output devices that perform both functions. Peripheral devices allow information to be retrieved from an external source and this usage of the term referred to a person who carried out calculations or computations. The word continued with the same meaning until the middle of the 20th century, from the end of the 19th century the word began to take on its more familiar meaning, a machine that carries out computations. The Online Etymology Dictionary gives the first attested use of computer in the 1640s, one who calculates, the Online Etymology Dictionary states that the use of the term to mean calculating machine is from 1897. The Online Etymology Dictionary indicates that the use of the term. 1945 under this name, theoretical from 1937, as Turing machine, devices have been used to aid computation for thousands of years, mostly using one-to-one correspondence with fingers. The earliest counting device was probably a form of tally stick, later record keeping aids throughout the Fertile Crescent included calculi which represented counts of items, probably livestock or grains, sealed in hollow unbaked clay containers. The use of counting rods is one example, the abacus was initially used for arithmetic tasks. The Roman abacus was developed from used in Babylonia as early as 2400 BC. Since then, many forms of reckoning boards or tables have been invented. In a medieval European counting house, a checkered cloth would be placed on a table, the Antikythera mechanism is believed to be the earliest mechanical analog computer, according to Derek J. de Solla Price. It was designed to calculate astronomical positions and it was discovered in 1901 in the Antikythera wreck off the Greek island of Antikythera, between Kythera and Crete, and has been dated to circa 100 BC
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Chemical reaction
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A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Nuclear chemistry is a sub-discipline of chemistry that involves the reactions of unstable. The substance initially involved in a reaction are called reactants or reagents. Chemical reactions are characterized by a chemical change, and they yield one or more products. Reactions often consist of a sequence of individual sub-steps, the elementary reactions. Chemical reactions are described with chemical equations, which present the starting materials, end products. Chemical reactions happen at a characteristic reaction rate at a given temperature, typically, reaction rates increase with increasing temperature because there is more thermal energy available to reach the activation energy necessary for breaking bonds between atoms. Reactions may proceed in the forward or reverse direction until they go to completion or reach equilibrium, Reactions that proceed in the forward direction to approach equilibrium are often described as spontaneous, requiring no input of free energy to go forward. Non-spontaneous reactions require input of energy to go forward. Different chemical reactions are used in combinations during chemical synthesis in order to obtain a desired product, in biochemistry, a consecutive series of chemical reactions form metabolic pathways. These reactions are catalyzed by protein enzymes. Chemical reactions such as combustion in fire, fermentation and the reduction of ores to metals were known since antiquity, in the Middle Ages, chemical transformations were studied by Alchemists. They attempted, in particular, to lead into gold, for which purpose they used reactions of lead. The process involved heating of sulfate and nitrate minerals such as sulfate, alum. In the 17th century, Johann Rudolph Glauber produced hydrochloric acid and sodium sulfate by reacting sulfuric acid, further optimization of sulfuric acid technology resulted in the contact process in the 1880s, and the Haber process was developed in 1909–1910 for ammonia synthesis. From the 16th century, researchers including Jan Baptist van Helmont, Robert Boyle, the phlogiston theory was proposed in 1667 by Johann Joachim Becher. It postulated the existence of an element called phlogiston, which was contained within combustible bodies. This proved to be false in 1785 by Antoine Lavoisier who found the explanation of the combustion as reaction with oxygen from the air
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Edward Teller
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Edward Teller was a Hungarian-American theoretical physicist who was born in Hungary, and is known colloquially as the father of the hydrogen bomb, although he claimed he did not care for the title. He made numerous contributions to nuclear and molecular physics, spectroscopy, Teller also made contributions to Thomas–Fermi theory, the precursor of density functional theory, a standard modern tool in the quantum mechanical treatment of complex molecules. Teller emigrated to the United States in the 1930s, and was an member of the Manhattan Project. During this time he made a push to develop the first fusion-based weapons as well. After his controversial testimony in the security clearance hearing of his former Los Alamos Laboratory superior J. Robert Oppenheimer, Teller was ostracized by much of the scientific community. He was a co-founder of Lawrence Livermore National Laboratory, and was both its director and associate director for many years and he was a vigorous advocate of Ronald Reagans Strategic Defense Initiative. Strangelove in the 1964 movie of the same name, ede Teller was born on January 15,1908, in Budapest, Hungary, into a Jewish family. His parents were Ilona, a pianist, and Max Teller, raised in a Jewish family, he later on became an agnostic. Religion was not an issue in my family, he wrote, indeed. My only religious training came because the Minta required that all students take classes in their respective religions and my family celebrated one holiday, the Day of Atonement, when we all fasted. Yet my father said prayers for his parents on Saturdays and on all the Jewish holidays, the idea of God that I absorbed was that it would be wonderful if He existed, We needed Him desperately but had not seen Him in many thousands of years. Like Einstein and Feynman, Teller was a late talker and he developed the ability to speak later than most children but became very interested in numbers, and would calculate large numbers in his head for fun. Teller left Hungary in 1926, partly due to the discriminatory numerus clausus rule under Miklós Horthys regime, the political climate and revolutions in Hungary during his youth instilled a lingering animosity for both Communism and Fascism in Teller. When he was a student, his right foot was severed in a streetcar accident in Munich, requiring him to wear a prosthetic foot. Werner Heisenberg said that it was the hardiness of Tellers spirit, rather than stoicism, Teller graduated in chemical engineering at the University of Karlsruhe, and received his Ph. D. in physics under Werner Heisenberg at the University of Leipzig. Tellers dissertation dealt with one of the first accurate quantum mechanical treatments of the molecular ion. In 1930 he befriended Russian physicists George Gamow and Lev Landau, Tellers lifelong friendship with a Czech physicist, George Placzek, was also very important for his scientific and philosophical development. It was Placzek who arranged a stay in Rome with Enrico Fermi in 1932
6.
J. Robert Oppenheimer
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Julius Robert Oppenheimer was an American theoretical physicist and professor of physics at the University of California, Berkeley. After the war, Oppenheimer became chairman of the influential General Advisory Committee of the newly created United States Atomic Energy Commission and he used that position to lobby for international control of nuclear power to avert nuclear proliferation and a nuclear arms race with the Soviet Union. Nine years later, President John F. Kennedy awarded him with the Enrico Fermi Award as a gesture of political rehabilitation. As a teacher and promoter of science, he is remembered as a father of the American school of theoretical physics that gained world prominence in the 1930s. After World War II, he director of the Institute for Advanced Study in Princeton. Julius came to America with no money, no baccalaureate studies and he got a job in a textile company and within a decade was an executive with the company. The Oppenheimers were non-observant Ashkenazi Jews, in 1912 the family moved to an apartment on the 11th floor of 155 Riverside Drive, near West 88th Street, Manhattan, an area known for luxurious mansions and townhouses. Their art collection included works by Pablo Picasso and Édouard Vuillard, Robert had a younger brother, Frank, who also became a physicist. Oppenheimer was initially educated at Alcuin Preparatory School, and in 1911 he entered the Ethical Culture Society School and this had been founded by Felix Adler to promote a form of ethical training based on the Ethical Culture movement, whose motto was Deed before Creed. His father had been a member of the Society for many years, Oppenheimer was a versatile scholar, interested in English and French literature, and particularly in mineralogy. He completed the third and fourth grades in one year, during his final year, he became interested in chemistry. He entered Harvard College a year late, at age 18, Oppenheimer majored in chemistry, but Harvard required science students to also study history, literature, and philosophy or mathematics. He compensated for his start by taking six courses each term and was admitted to the undergraduate honor society Phi Beta Kappa. He was attracted to physics by a course on thermodynamics that was taught by Percy Bridgman. He graduated summa cum laude in three years, in 1924 Oppenheimer was informed that he had been accepted into Christs College, Cambridge. He wrote to Ernest Rutherford requesting permission to work at the Cavendish Laboratory, Bridgman provided Oppenheimer with a recommendation, which conceded that Oppenheimers clumsiness in the laboratory made it apparent his forte was not experimental but rather theoretical physics. Rutherford was unimpressed, but Oppenheimer went to Cambridge in the hope of landing another offer and he was ultimately accepted by J. J. Thomson on condition that he complete a basic laboratory course. He developed a relationship with his tutor, Patrick Blackett
7.
Linus Pauling
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Linus Carl Pauling was an American chemist, biochemist, peace activist, author, and educator. He published more than 1,200 papers and books, of which about 850 dealt with scientific topics, new Scientist called him one of the 20 greatest scientists of all time, and as of 2000, he was rated the 16th most important scientist in history. Pauling was one of the founders of the fields of quantum chemistry, for his scientific work, Pauling was awarded the Nobel Prize in Chemistry in 1954. In 1962, for his activism, he was awarded the Nobel Peace Prize. This makes him the person to be awarded two unshared Nobel Prizes. He is one of four individuals to have won more than one Nobel Prize. Pauling is also one of two people to be awarded Nobel Prizes in different fields, the other being Marie Curie. Pauling also worked on DNAs structure, a problem which was solved by James Watson, Francis Crick, Rosalind Franklin, in his later years he promoted nuclear disarmament, as well as orthomolecular medicine, megavitamin therapy, and dietary supplements. None of the latter have gained acceptance in the scientific community. Pauling was born in Portland, Oregon, the child of Herman Henry William Pauling. He was named Linus Carl, in honor of Lucys father, Linus, in 1902, after his sister Pauline was born, Paulings parents decided to move out of Portland, to find more affordable and spacious living quarters than their one-room apartment. Lucy stayed with her husbands parents in Lake Oswego until Herman brought the family to Salem, within a year of Luciles birth in 1904, Herman Pauling moved his family to Oswego, where he opened his own drugstore. He moved his family to Condon, Oregon in 1905, by 1906, Herman Pauling was suffering from recurrent abdominal pain. He died of an ulcer on June 11,1910, leaving Lucy to care for Linus, Lucile. Pauling attributes his interest in becoming a chemist to being amazed by experiments conducted by a friend, Lloyd A. Jeffress, in high school, Pauling conducted chemistry experiments by scavenging equipment and material from an abandoned steel plant. With an older friend, Lloyd Simon, Pauling set up Palmon Laboratories in Simons basement and they approached local dairies offering to perform butterfat samplings at cheap prices but dairymen were wary of trusting two boys with the task, and the business ended in failure. At age 15, the high school senior had enough credits to enter Oregon State University, lacking two American history courses required for his high school diploma, Pauling asked the school principal if he could take the courses concurrently during the spring semester. Denied, he left Washington High School in June without a diploma, the school awarded him a diploma 45 years later, after he had won two Nobel Prizes
8.
Cathode ray
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Cathode rays are streams of electrons observed in vacuum tubes. They were first observed in 1869 by German physicist Johann Hittorf, electrons were discovered as the constituents of cathode rays. In 1897 British physicist J. J. Thomson showed the rays were composed of a previously unknown negatively charged particle, Cathode ray tubes use a focused beam of electrons deflected by electric or magnetic fields to create the image in a classic television set. Cathode rays are made up of charged particles. Cathode rays are so named because they are emitted by the electrode, or cathode. This contrasts with cations, which are charged and go — Greek ἰόν — toward a cathode in solution. To release electrons into the tube, they first must be detached from the atoms of the cathode, modern vacuum tubes use thermionic emission, in which the cathode is made of a thin wire filament which is heated by a separate electric current passing through it. The increased random heat motion of the filament knocks electrons out at the surface of the filament, since the electrons have a negative charge, they are repelled by the cathode and attracted to the anode. They travel in straight lines through the empty tube, the voltage applied between the electrodes accelerates these low mass particles to high velocities. Researchers noticed that objects placed in the tube in front of the cathode could cast a shadow on the glowing wall, and realized that something must be travelling in straight lines from the cathode. After the electrons reach the anode, they travel through the wire to the power supply and back to the cathode. The current in a beam of cathode rays through a tube can be controlled by passing it through a screen of wires to which a small voltage is applied. The electric field of the wires deflects some of the electrons, thus a small voltage on the grid can be made to control a much larger voltage on the anode. This is the used in vacuum tubes to amplify electrical signals. These are used in cathode ray tubes, found in televisions and computer monitors, after the 1654 invention of the vacuum pump by Otto von Guericke, physicists began to experiment with passing high voltage electricity through rarefied air. In 1705, it was noted that electrostatic generator sparks travel a distance through low pressure air than through atmospheric pressure air. In 1838, Michael Faraday passed a current through an air filled glass tube and noticed a strange light arc with its beginning at the cathode. In 1857, German physicist and glassblower Heinrich Geissler sucked even more air out with a pump, to a pressure of around 10−3 atm and found that, instead of an arc
9.
Michael Faraday
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Michael Faraday FRS was an English scientist who contributed to the study of electromagnetism and electrochemistry. His main discoveries include the principles underlying electromagnetic induction, diamagnetism, although Faraday received little formal education, he was one of the most influential scientists in history. It was by his research on the field around a conductor carrying a direct current that Faraday established the basis for the concept of the electromagnetic field in physics. Faraday also established that magnetism could affect rays of light and that there was a relationship between the two phenomena. He similarly discovered the principles of induction and diamagnetism. His inventions of electromagnetic rotary devices formed the foundation of electric motor technology, Faraday ultimately became the first and foremost Fullerian Professor of Chemistry at the Royal Institution of Great Britain, a lifetime position. James Clerk Maxwell took the work of Faraday and others and summarized it in a set of equations which is accepted as the basis of all theories of electromagnetic phenomena. The SI unit of capacitance is named in his honour, the farad, albert Einstein kept a picture of Faraday on his study wall, alongside pictures of Isaac Newton and James Clerk Maxwell. Faraday was born in Newington Butts, which is now part of the London Borough of Southwark but was then a part of Surrey. His family was not well off and his father, James, was a member of the Glassite sect of Christianity. James Faraday moved his wife and two children to London during the winter of 1790 from Outhgill in Westmorland, where he had been an apprentice to the village blacksmith, Michael was born in the autumn of that year. The young Michael Faraday, who was the third of four children, at the age of 14 he became an apprentice to George Riebau, a local bookbinder and bookseller in Blandford Street. During his seven-year apprenticeship Faraday read many books, including Isaac Wattss The Improvement of the Mind, at this time he also developed an interest in science, especially in electricity. Faraday was particularly inspired by the book Conversations on Chemistry by Jane Marcet, many of the tickets for these lectures were given to Faraday by William Dance, who was one of the founders of the Royal Philharmonic Society. Faraday subsequently sent Davy a 300-page book based on notes that he had taken during these lectures, davys reply was immediate, kind, and favourable. In 1813, when Davy damaged his eyesight in an accident with nitrogen trichloride, very soon Davy entrusted Faraday with the preparation of nitrogen trichloride samples, and they both were injured in an explosion of this very sensitive substance. In the class-based English society of the time, Faraday was not considered a gentleman, Faraday was forced to fill the role of valet as well as assistant throughout the trip. Davys wife, Jane Apreece, refused to treat Faraday as an equal, the trip did, however, give him access to the scientific elite of Europe and exposed him to a host of stimulating ideas
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Gustav Kirchhoff
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Gustav Robert Kirchhoff was a German physicist who contributed to the fundamental understanding of electrical circuits, spectroscopy, and the emission of black-body radiation by heated objects. He coined the term black body radiation in 1862, and two different sets of concepts are named Kirchhoffs laws after him, there is also a Kirchhoffs Law in thermochemistry, the Bunsen–Kirchhoff Award for spectroscopy is named after him and his colleague, Robert Bunsen. Gustav Kirchhoff was born in Königsberg, Prussia, the son of Friedrich Kirchhoff, a lawyer, in the same year, he moved to Berlin, where he stayed until he received a professorship at Breslau. Later, in 1857, He married Clara Richelot, the daughter of his mathematics professor Richelot and he married Luise Brömmel in 1872. Kirchhoff formulated his laws, which are now ubiquitous in electrical engineering, in 1845. He completed this study as an exercise, it later became his doctoral dissertation. In 1857 he calculated that a signal in a resistanceless wire travels along the wire at the speed of light. He proposed his law of radiation in 1859, and gave a proof in 1861. He was called to the University of Heidelberg in 1854, where he collaborated in work with Robert Bunsen. Together Kirchhoff and Bunsen discovered caesium and rubidium in 1861, at Heidelberg he ran a mathematico-physical seminar, modelled on Neumanns, with the mathematician Leo Koenigsberger. Among those who attended this seminar were Arthur Schuster and Sofia Kovalevskaya, in 1875 Kirchhoff accepted the first chair specifically dedicated to theoretical physics at Berlin. In 1862 he was awarded the Rumford Medal for his researches on the lines of the solar spectrum. He also contributed to optics, carefully solving Maxwells equations to provide a foundation for Huygens principle. In 1884 he became member of the Royal Netherlands Academy of Arts. Kirchhoff died in 1887, and was buried in the St Matthäus Kirchhof Cemetery in Schöneberg, leopold Kronecker is buried in the same cemetery. Kirchhoffs first law is that the sum of currents in a network of conductors meeting at a point is zero. The second law is that in a circuit, the directed sums of the voltages in a closed system is zero. A solid, liquid, or dense gas excited to emit light will radiate at all wavelengths, a low-density gas excited to emit light will do so at specific wavelengths and this produces an emission spectrum
