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#1 Re: This is Cool » Miscellany » Today 01:13:50

1124) Aluminum

Aluminum (Al), also spelled aluminium, chemical element, a lightweight, silvery-white metal of main Group 13 (IIIa, or boron group) of the periodic table. Aluminum is the most abundant metallic element in Earth’s crust and the most widely used nonferrous metal. Because of its chemical activity, aluminum never occurs in the metallic form in nature, but its compounds are present to a greater or lesser extent in almost all rocks, vegetation, and animals. Aluminum is concentrated in the outer 10 miles (16 km) of Earth’s crust, of which it constitutes about 8 percent by weight; it is exceeded in amount only by oxygen and silicon. The name aluminum is derived from the Latin word alumen, used to describe potash alum, or aluminum potassium sulfate, KAl(SO4)2∙12H2O.

Element Properties

atomic number  :  13
atomic weight  :  26.9815
melting point  :  660 °C (1,220 °F)
boiling point  :  2,467 °C (4,473 °F)
specific gravity  :  2.70 (at 20 °C [68 °F])
valence  :  3

Occurrence, Uses, And Properties

Aluminum occurs in igneous rocks chiefly as aluminosilicates in feldspars, feldspathoids, and micas; in the soil derived from them as clay; and upon further weathering as bauxite and iron-rich laterite. Bauxite, a mixture of hydrated aluminum oxides, is the principal aluminum ore. Crystalline aluminum oxide (emery, corundum), which occurs in a few igneous rocks, is mined as a natural abrasive or in its finer varieties as rubies and sapphires. Aluminum is present in other gemstones, such as topaz, garnet, and chrysoberyl. Of the many other aluminum minerals, alunite and cryolite have some commercial importance.

Crude aluminum was isolated (1825) by Danish physicist Hans Christian Ørsted by reducing aluminum chloride with potassium amalgam. British chemist Sir Humphry Davy had prepared (1809) an iron-aluminum alloy by electrolyzing fused alumina (aluminum oxide) and had already named the element aluminum; the word later was modified to aluminium in England and some other European countries. German chemist Friedrich Wöhler, using potassium metal as the reducing agent, produced aluminum powder (1827) and small globules of the metal (1845), from which he was able to determine some of its properties.

The new metal was introduced to the public (1855) at the Paris Exposition at about the time that it became available (in small amounts at great expense) by the sodium reduction of molten aluminum chloride. When electric power became relatively plentiful and cheap, almost simultaneously Charles Martin Hall in the United States and Paul-Louis-Toussaint Héroult in France discovered (1886) the modern method of commercially producing aluminum: electrolysis of purified alumina (Al2O3) dissolved in molten cryolite (Na3AlF6). During the 1960s aluminum moved into first place, ahead of copper, in world production of nonferrous metals.

Aluminum is added in small amounts to certain metals to improve their properties for specific uses, as in aluminum bronzes and most magnesium-base alloys; or, for aluminum-base alloys, moderate amounts of other metals and silicon are added to aluminum. The metal and its alloys are used extensively for aircraft construction, building materials, consumer durables (refrigerators, air conditioners, cooking utensils), electrical conductors, and chemical and food-processing equipment.

Pure aluminum (99.996 percent) is quite soft and weak; commercial aluminum (99 to 99.6 percent pure) with small amounts of silicon and iron is hard and strong. Ductile and highly malleable, aluminum can be drawn into wire or rolled into thin foil. The metal is only about one-third as dense as iron or copper. Though chemically active, aluminum is nevertheless highly corrosion-resistant, because in air a hard, tough oxide film forms on its surface.

Aluminum is an excellent conductor of heat and electricity. Its thermal conductivity is about one-half that of copper; its electrical conductivity, about two-thirds. It crystallizes in the face-centred cubic structure. All natural aluminum is the stable isotope aluminum-27. Metallic aluminum and its oxide and hydroxide are nontoxic.

Aluminum is slowly attacked by most dilute acids and rapidly dissolves in concentrated hydrochloric acid. Concentrated nitric acid, however, can be shipped in aluminum tank cars because it renders the metal passive. Even very pure aluminum is vigorously attacked by alkalies such as sodium and potassium hydroxide to yield hydrogen and the aluminate ion. Because of its great affinity for oxygen, finely divided aluminum, if ignited, will burn in carbon monoxide or carbon dioxide with the formation of aluminum oxide and carbide, but, at temperatures up to red heat, aluminum is inert to sulfur.

Aluminum can be detected in concentrations as low as one part per million by means of emission spectroscopy. Aluminum can be quantitatively analyzed as the oxide (formula Al2O3) or as a derivative of the organic nitrogen compound 8-hydroxyquinoline. The derivative has the molecular formula Al(C9H6ON)3.

Compounds

Ordinarily, aluminum is trivalent. At elevated temperatures, however, a few gaseous monovalent and bivalent compounds have been prepared (AlCl, Al2O, AlO). In aluminum the configuration of the three outer electrons is such that in a few compounds (e.g., crystalline aluminum fluoride [AlF3] and aluminum chloride [AlCl3]) the bare ion, Al3+, formed by loss of these electrons, is known to occur. The energy required to form the Al3+ ion, however, is very high, and, in the majority of cases, it is energetically more favourable for the aluminum atom to form covalent compounds by way of sp2 hybridization, as boron does. The Al3+ ion can be stabilized by hydration, and the octahedral ion [Al(H2O)6]3+ occurs both in aqueous solution and in several salts.

A number of aluminum compounds have important industrial applications. Alumina, which occurs in nature as corundum, is also prepared commercially in large quantities for use in the production of aluminum metal and the manufacture of insulators, spark plugs, and various other products. Upon heating, alumina develops a porous structure, which enables it to adsorb water vapour. This form of aluminum oxide, commercially known as activated alumina, is used for drying gases and certain liquids. It also serves as a carrier for catalysts of various chemical reactions.

Anodic aluminum oxide (AAO), typically produced via the electrochemical oxidation of aluminum, is a nanostructured aluminum-based material with a very unique structure. AAO contains cylindrical pores that provide for a variety of uses. It is a thermally and mechanically stable compound while also being optically transparent and an electrical insulator. The pore size and thickness of AAO can easily be tailored to fit certain applications, including acting as a template for synthesizing materials into nanotubes and nanorods.

Another major compound is aluminum sulfate, a colourless salt obtained by the action of sulfuric acid on hydrated aluminum oxide. The commercial form is a hydrated crystalline solid with the chemical formula Al2(SO4)3. It is used extensively in paper manufacture as a binder for dyes and as a surface filler. Aluminum sulfate combines with the sulfates of univalent metals to form hydrated double sulfates called alums. The alums, double salts of formula MAl(SO4)2 ·12H2O (where M is a singly charged cation such as K+), also contain the Al3+ ion; M can be the cation of sodium, potassium, rubidium, cesium, ammonium, or thallium, and the aluminum may be replaced by a variety of other M3+ ions—e.g., gallium, indium, titanium, vanadium, chromium, manganese, iron, or cobalt. The most important of such salts is aluminum potassium sulfate, also known as potassium alum or potash alum. These alums have many applications, especially in the production of medicines, textiles, and paints.

The reaction of gaseous chlorine with molten aluminum metal produces aluminum chloride; the latter is the most commonly used catalyst in Friedel-Crafts reactions—i.e., synthetic organic reactions involved in the preparations of a wide variety of compounds, including aromatic ketones and anthroquinone and its derivatives. Hydrated aluminum chloride, commonly known as aluminum chlorohydrate, AlCl3∙H2O, is used as a topical antiperspirant or body deodorant, which acts by constricting the pores. It is one of several aluminum salts employed by the cosmetics industry.

Aluminum hydroxide, Al(OH)3, is used to waterproof fabrics and to produce a number of other aluminum compounds, including salts called aluminates that contain the AlO−2 group. With hydrogen, aluminum forms aluminum hydride, AlH3, a polymeric solid from which are derived the tetrohydroaluminates (important reducing agents). Lithium aluminum hydride (LiAlH4), formed by the reaction of aluminum chloride with lithium hydride, is widely used in organic chemistry—e.g., to reduce aldehydes and ketones to primary and secondary alcohols, respectively.

iStock-538025236.jpg

#2 Jokes » More Sundry Jokes - 25 » Today 01:01:39

ganesh
Replies: 0

Q: What did the hamburger name her daughter?
A: Patty.
* * *
Q: What do a car and an elephant have in common?
A: They both have trunks.
* * *
Knock, knock.
Who’s there?
Tank.
Tank who?
You’re welcome!
* * *
Q: Why do cowboys ride horses?
A: Because they’re too heavy to carry.
* * *
Q: What is a math teacher’s favorite type of dessert?
A: Pi.
* * *

#5 Re: Ganesh's Puzzles » General Quiz » Today 00:14:22

Hi,

#8013. What does the term 'Balneotherapy' mean?

#8014. What does the term 'Batrachology' mean?

#6 Re: Ganesh's Puzzles » Doc, Doc! » Today 00:13:51

Hi,

#1716. What does the medical term 'Myenteric plexus' mean?

#7 Re: Ganesh's Puzzles » English language puzzles » Yesterday 00:31:37

Hi,

#4087. What does the noun footstool mean?

#4088. What does the noun footwear mean?

#8 Re: Dark Discussions at Cafe Infinity » crème de la crème » Yesterday 00:17:39

942) Raman Sukumar

Raman Sukumar, (born April 3, 1955, Madras [now Chennai], India), Indian ecologist best known for his work on the behaviour of Asian elephants and how their presence has affected both human and natural environments.

As a child growing up in Madras, Sukumar was dubbed ‘vanavasi’ (the Tamil word for “forest dweller”) by his grandmother. It was during his secondary-school years that Sukumar first developed an interest in the field of conservation. He graduated from the University of Madras with bachelor’s (1977) and master’s (1979) degrees in botany. In 1979 he began studies for his doctoral thesis at the Indian Institute of Science, where he focused on the ecological conflict that occurs when elephants and humans use the same land. He received his doctorate in ecology in 1985 and became a professor at the Centre for Ecological Sciences, attached to the Indian Institute of Science, in 1986. Sukumar later became a Fulbright scholar and completed a postdoctoral fellowship (1991–92) at Princeton University.

In an effort to provide a safe habitat for elephants, Sukumar carried out surveys and tried to establish protected corridors so that elephant herds could move from one reserve to another. He experimented with various forms of fences around village perimeters to keep the animals away from crops and human habitation. Sukumar also helped design the Nilgiri Biosphere Reserve, the first of its kind in India, which was established in 1986. There he conducted research on climate change, tropical forests, and wildlife conservation.

In 1993 Sukumar became a member of the Project Elephant Steering Committee, which provided technical support and advice on matters of elephant conservation to the Indian government. He chaired the Asian Elephant Specialist Group of the World Conservation Union from 1997 to 2004. Sukumar also served as director of the Asian Elephant Research and Conservation Centre, a special division of the Asian Nature Conservation Foundation, an independent organization that he had helped to establish in 1997. The foundation worked closely with many governmental and nongovernmental agencies in the region to determine how to best conserve elephant habitat and manage human-elephant conflict. He published several notable texts on elephants, including ‘Elephant Days and Nights: Ten Years with the Indian Elephant’ (1994), ‘The Living Elephants: Evolutionary Ecology, Behavior and Conservation’ (2003), and ‘The Story of Asia’s Elephants’ (2011).

Sukumar’s accolades included the Presidential Award of the Chicago Zoological Society in 1989 and the Order of the Golden Ark in 1997. He became a fellow of the Indian Academy of Sciences in 2000 and was inducted into the Indian National Science Academy in 2004. Sukumar was presented with the Whitley Gold Award in 2003 and with the International Cosmos Prize in 2006.

SukumarRaman400x300.jpg?ssl=1

#9 Re: Ganesh's Puzzles » Doc, Doc! » Yesterday 00:05:58

Hi,

#1715. What does the medical term 'Coronary catheterization' mean?

#12 Re: Ganesh's Puzzles » English language puzzles » 2021-09-25 01:26:30

Hi,

#4085. What does the noun footstep mean?

#4086. What does the adjective footsore mean?

#13 Re: This is Cool » Miscellany » 2021-09-25 00:53:46

1123) Cesium

Cesium (Cs), also spelled caesium, chemical element of Group 1 (also called Group Ia) of the periodic table, the alkali metal group, and the first element to be discovered spectroscopically (1860), by German scientists Robert Bunsen and Gustav Kirchhoff, who named it for the unique blue lines of its spectrum (Latin caesius, “sky-blue”).

This silvery metal with a golden cast is the most reactive and one of the softest of all metals. It melts at 28.4 °C (83.1 °F), just above room temperature. It is about half as abundant as lead and 70 times as abundant as silver. Cesium occurs in minute quantities (7 parts per million) in Earth’s crust in the minerals pollucite, rhodizite, and lepidolite. Pollucite (Cs4Al4Si9O26∙H2O) is a cesium-rich mineral resembling quartz. It contains 40.1 percent cesium on a pure basis, and impure samples are ordinarily separated by hand-sorting methods to greater than 25 percent cesium. Large pollucite deposits have been found in Zimbabwe and in the lithium-bearing pegmatites at Bernic Lake, Manitoba, Canada. Rhodizite is a rare mineral found in low concentrations in lepidolite and in salt brines and saline deposits.

The primary difficulty associated with the production of pure cesium is that cesium is always found together with rubidium in nature and is also mixed with other alkali metals. Because cesium and rubidium are very similar chemically, their separation presented numerous problems before the advent of ion-exchange methods and ion-specific complexing agents such as crown ethers. Once pure salts have been prepared, it is a straightforward task to convert them to the free metal.

Cesium can be isolated by electrolysis of a molten cesium cyanide/barium cyanide mixture and by other methods, such as reduction of its salts with sodium metal, followed by fractional distillation. Cesium reacts explosively with cold water; it readily combines with oxygen, so it is used in vacuum tubes as a “getter” to clear out the traces of oxygen and other gases trapped in the tube when sealed. The very pure gas-free cesium needed as a “getter” for oxygen in vacuum tubes can be produced as needed by heating cesium azide (CsN3) in a vacuum. Because cesium is strongly photoelectric (easily loses electrons when struck by light), it is used in photoelectric cells, photomultiplier tubes, scintillation counters, and spectrophotometers. It is also used in infrared lamps. Because the cesium atom can be ionized thermally and the positively charged ions accelerated to great speeds, cesium systems could provide extraordinarily high exhaust velocities for plasma propulsion engines for deep-space exploration.

Cesium metal is produced in rather limited amounts because of its relatively high cost. Cesium has application in thermionic power converters that generate electricity directly within nuclear reactors or from the heat produced by radioactive decay. Another potential application of cesium metal is in the production of low-melting NaKCs eutectic alloy.

Atomic cesium is employed in the world’s time standard, the cesium clock. The microwave spectral line emitted by the isotope cesium-133 has a frequency of 9,192,631,770 hertz (cycles per second). This provides the fundamental unit of time. Cesium clocks are so stable and accurate that they are reliable to 1 second in 1.4 million years. Primary standard cesium clocks, such as NIST-F1 in Boulder, Colo., are about as large as a railroad flatcar. Commercial secondary standards are suitcase-sized.

Naturally occurring cesium consists entirely of the nonradioactive isotope cesium-133; a large number of radioactive isotopes from cesium-123 to cesium-144 have been prepared. Cesium-137 is useful in medical and industrial radiology because of its long half-life of 30.17 years. However, as a major component of nuclear fallout and a waste product left over from the production of plutonium and other enriched nuclear fuels, it presents an environmental hazard. Removal of radioactive cesium from contaminated soil at nuclear-weapon-production sites, such as Oak Ridge National Laboratory in Oak Ridge, Tennessee, and the U.S. Department of Energy’s Hanford site near Richland, Washington, is a major cleanup effort.

Cesium is difficult to handle because it reacts spontaneously in air. If a metal sample has a large enough surface area, it can burn to form superoxides. Cesium superoxide has a more reddish cast. Cs2O2 can be formed by oxidation of the metal with the required amount of oxygen, but other reactions of cesium with oxygen are much more complex.

Cesium is the most electropositive and most alkaline element, and thus, more easily than all other elements, it loses its single valence electron and forms ionic bonds with nearly all the inorganic and organic anions. The anion Cs– has also been prepared. Cesium hydroxide (CsOH), containing the hydroxide anion (OH–), is the strongest base known, attacking even glass. Some cesium salts are used in making mineral waters. Cesium forms a number of mercury amalgams. Because of the increased specific volume of cesium, as compared with the lighter alkali metals, there is a lesser tendency for it to form alloy systems with other metals.

Rubidium and cesium are miscible in all proportions and have complete solid solubility; a melting-point minimum of 9 °C (48 °F) is reached.

Element Properties

atomic number  :  55
atomic weight  :  132.90543
melting point  :  28.44 °C (83.19 °F)
boiling point  :  671 °C (1,240 °F)
specific gravity  :  1.873 (at 20 °C, or 68 °F)
oxidation states  :  +1, -1 (rare).

Cesium.png

#14 Jokes » More Sundry Jokes - 24 » 2021-09-25 00:41:09

ganesh
Replies: 0

Q: What’s a rabbit’s favorite kind of music?
A: Hip-hop.
* * *
Q: Where’s a wall’s favorite place to meet his friends?
A: At the corner.
* * *
Q: Where did the king keep his army?
A: In his sleeve.
* * *
Q: Why don’t animals eat clowns?
A: They taste funny!
* * *
Q: Where do books hide when they’re scared?
A: Under their covers.
* * *

#15 Re: Ganesh's Puzzles » General Quiz » 2021-09-25 00:17:17

Hi,

#8011. What does the term 'Arthrology' mean?

#8012. What does the term 'Auxology' mean?

#20 Re: Dark Discussions at Cafe Infinity » crème de la crème » 2021-09-24 00:41:41

941) Ray Kurzweil

Ray Kurzweil, byname of Raymond Kurzweil, (born February 12, 1948, Queens, New York, U.S.), American computer scientist and futurist who pioneered pattern-recognition technology and proselytized the inevitability of humanity’s merger with the technology it created.

Kurzweil was raised in a secular Jewish family in Queens, New York. His parents fostered an early interest in science, allowing him to work as a computer programmer for the Head Start program at age 14. In 1965 he earned first prize in the International Science Fair with a computer program that could write music that mimicked the styles of great composers. The program marked the beginning of his career-long attempt to re-create pattern recognition, or the ability to find order in complex data. It was Kurzweil’s belief that pattern recognition formed the basis of human thought.

As a student at the Massachusetts Institute of Technology (MIT), Kurzweil created a computer program that helped high-school students choose a college to attend. He then sold the service to a publisher for $100,000 plus royalties. He graduated from MIT in 1970 with a bachelor’s degree in computer science and literature. Four years later he established Kurzweil Computer Products, Inc., which developed technology that allowed computers to read text printed in any normal typeface. Under Kurzweil’s direction, the company also pioneered a flatbed scanner and a text-to-speech synthesizer and used all three inventions to build a reading machine for the blind. A commercial version of the machine was developed, which led to the sale of the company to the Xerox Corporation in 1980; Kurzweil was a consultant for Xerox until 1995. A friendship with musician Stevie Wonder led Kurzweil to launch a business that created professional-quality music synthesizers in 1982. That venture was sold to the Korean instrument manufacturer Young Chang in 1990.

In 1987 another company founded by Kurzweil spawned the first commercial speech-recognition system and in 1997 was sold to a concern that later teamed with the Microsoft Corporation to market speech-recognition software for personal computers. In 1997 and 1999 he founded firms that produced software using artificial intelligence for financial analysis and medical training. Kurzweil also explored the possibilities of technology in creating art, founding a company in 1998 that produced software capable of creating paintings and poetry. His Web site, KurzweilAI.net, was founded in 2001 and featured articles on the future of technology, as well as Ramona, a virtual-reality woman who conversed with users. In 2003 Kurzweil cofounded a company that sold nutritional supplements aimed at extending the human life span, and in 2005 he cofounded a company that released a handheld print reader for the blind.

Kurzweil attracted the attention of the general public with his daring prognostications about how technology would shape the future. He explicated an array of prescient theories in ‘The Age of Intelligent Machines’ (1990), which anticipated the explosion in popularity of the Internet. Kurzweil also wrote ‘The 10% Solution for a Healthy Life’ (1993), which details a diet that he had used to help cure himself of diabetes. His book ‘The Age of Spiritual Machines’ (1999) presents a vision of the 21st century as a time when computer technology would have advanced far enough to allow machines to operate on a level equivalent to that of the human brain. Computers, he predicted, would make complex decisions, appreciate beauty, and even experience emotions. Moreover, Kurzweil believed that as humans transferred the information in their brains to computers, the distinction between man and machine would become blurred. He further augured the convergence of human life with technology in ‘Fantastic Voyage: Live Long Enough to Live Forever’ (2004), coauthored with Terry Grossman, and ‘The Singularity Is Near: When Humans Transcend Biology’ (2005). ‘Transcendent Man’ (2009), a documentary, chronicles Kurzweil’s life and features interviews with both supporters and detractors of his predictions.

In 2000 Kurzweil was awarded the U.S. National Medal of Technology in recognition of his many innovations. He was inducted into the National Inventors Hall of Fame, established by the U.S. Patent Office, in 2002.

Ray-Kurzweil.jpg

#21 Re: Ganesh's Puzzles » Doc, Doc! » 2021-09-24 00:28:21

Hi,

#1714. What does the medical term 'Sternocleidomastoid muscle' mean?

#22 Re: Ganesh's Puzzles » English language puzzles » 2021-09-24 00:18:36

Hi,

#4083. What does the noun footplate mean?

#4084. What does the noun footprint mean?

#25 Re: Ganesh's Puzzles » 10 second questions » 2021-09-23 14:17:36

Hi T897T and phrontister,

#8112.

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