Chemistry - New World Encyclopedia

à 27 avril

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Explains what structural isomerism is and the various ways that...

The word is a structural and semantic entity within the language system. It should be pointed out that there is another approach to the concept of the basic language unit. groups consisting of two or more words whose combination is integrated as a unit with a specialised meaning of the whole.Which of the following are typically seen as being associated with strategic decisions? A. The organisation's long-term direction B. The detailed planning of a department's work over the next month C. The values and expectations Which are the two most common types of governance structure?One of the most important industries is the food industry, because every day the human body requires fuel of various food products Classification of food products is a logical process of dividing the whole set of food products into groups of different levels of generality according to certain characteristics.Minerals are the foundation of the construction, manufacturing and agricultural industries. The white "m" on a piece of M&M's candy is a titanium oxide pigment, most likely produced from the mineral rutile. Structure of the mineral halite: The mineral "halite" has a chemical composition of NaCl.

Compounds and Mixtures Reading Comprehension

To create the wide variety of silicate minerals, this pyramid-shaped structure is often bound to other elements, such as calcium, iron, and magnesium. The sulfate group contains many different minerals, but only a few are common. Gypsum is a common sulfate with a variety of appearances...The structure of the world we commonly experience and the properties of the matter we Modern Transmutation is a large component of nuclear chemistry, and the table of nuclides is an important The most familiar examples of phases are solids, liquids, and gases. Less familiar phases include...In general stone is used as basic structural components in the buildings, while mud is used to fill in the space between, acting as a type of concrete Common plantmaterials include wood and various fibers such as cotton. Animal materials include leather and fibers suchas wool.Wood is a valuable...Which of the following forces can stabilize a normal DNA double-helix? a) Base-stacking is a non-covalent interaction that occurs between the. Which describes the structural properties of a eukaryotic chromosome? a) It contains a double-helix composed of nucleosomes each with four.The biotic components can be further grouped into two basic components from the nutrition point of view Some of the most common terrestrial ecosystems that are found are the following Function of Ecosystem. An ecosystem is a discrete structural, functional and life-sustaining...

Mineral, naturally occurring homogeneous solid with a definite chemical composition and a highly ordered atomic arrangement; it is usually formed by inorganic processes. There are several thousand known mineral species, about 100 of which constitute the major mineral components of rocks; these are the so-called rock-forming minerals.

azuriteAzurite, also called chessylite, is a basic copper carbonate ordinarily found with malachite in the oxidized zone of copper lodes.© Rainer Walter Schmied/Dreamstime.com

Britannica Quiz

Rocks and Minerals: Fact or Fiction?

Is the Grand Canyon 2 billion years old? Can you find magnesium in the sea? Rock your knowledge of rocks and minerals in this quiz.

Definition

Observe the formation of salt crystal through the crystallization processUnit cells cluster together to form crystals in a process called crystallization.Created and produced by QA International. © QA International, 2010. All rights reserved. www.qa-international.comSee all videos for this article

A mineral, which by definition must be formed through natural processes, is distinct from the synthetic equivalents produced in the laboratory. Artificial versions of minerals, including emeralds, sapphires, diamonds, and other valuable gemstones, are regularly produced in industrial and research facilities and are often nearly identical to their natural counterparts.

By its definition as a homogeneous solid, a mineral is composed of a single solid substance of uniform composition that cannot be physically separated into simpler chemical compounds. Homogeneity is determined relative to the scale on which it is defined. A specimen that appears homogeneous to the unaided eye, for example, may reveal several mineral components under a microscope or upon exposure to X-ray diffraction techniques. Most rocks are composed of several different minerals; e.g., granite consists of feldspar, quartz, mica, and amphibole. In addition, gases and liquids are excluded by a strict interpretation of the above definition of a mineral. Ice, the solid state of water (H2O), is considered a mineral, but liquid water is not; liquid mercury, though sometimes found in mercury ore deposits, is not classified as a mineral either. Such substances that resemble minerals in chemistry and occurrence are dubbed mineraloids and are included in the general domain of mineralogy.

Since a mineral has a definite composition, it can be expressed by a specific chemical formula. Quartz (silicon dioxide), for instance, is rendered as SiO2, because the elements silicon (Si) and oxygen (O) are its only constituents and they invariably appear in a 1:2 ratio. The chemical makeup of most minerals is not as well defined as that of quartz, which is a pure substance. Siderite, for example, does not always occur as pure iron carbonate (FeCO3); magnesium (Mg), manganese (Mn), and, to a limited extent, calcium (Ca) may sometimes substitute for the iron. Since the amount of the replacement may vary, the composition of siderite is not fixed and ranges between certain limits, although the ratio of the metal cation to the anionic group remains fixed at 1:1. Its chemical makeup may be expressed by the general formula (Fe, Mn, Mg, Ca)CO3, which reflects the variability of the metal content.

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Minerals display a highly ordered internal atomic structure that has a regular geometric form. Because of this feature, minerals are classified as crystalline solids. Under favourable conditions, crystalline materials may express their ordered internal framework by a well-developed external form, often referred to as crystal form or morphology. Solids that exhibit no such ordered internal arrangement are termed amorphous. Many amorphous natural solids, such as glass, are categorized as mineraloids.

pyriteSchematic representation of the structure of pyrite (FeS2) as based on a cubic array of ferrous iron cations (Fe2+) and sulfur anions (S−).Encyclopædia Britannica, Inc.

Traditionally, minerals have been described as resulting exclusively from inorganic processes; however, current mineralogic practice often includes as minerals those compounds that are organically produced but satisfy all other mineral requirements. Aragonite (CaCO3) is an example of an inorganically formed mineral that also has an organically produced, yet otherwise identical, counterpart; the shell (and the pearl, if it is present) of an oyster is composed to a large extent of organically formed aragonite. Minerals also are produced by the human body: hydroxylapatite [Ca5(PO4)3(OH)] is the chief component of bones and teeth, and calculi are concretions of mineral substances found in the urinary system.

Nomenclature

While minerals are classified in a logical manner according to their major anionic (negatively charged) chemical constituents into groups such as oxides, silicates, and nitrates, they are named in a far less scientific or consistent way. Names may be assigned to reflect a physical or chemical property, such as colour, or they may be derived from various subjects deemed appropriate, such as, for example, a locality, public figure, or mineralogist. Some examples of mineral names and their derivations follow: albite (NaAlSi3O8) is from the Latin word (albus) for "white" in reference to its colour; goethite (FeO ∙ OH) is in honour of Johann Wolfgang von Goethe, the German poet; manganite (MnO ∙ OH) reflects the mineral's composition; franklinite (ZnFe2O4) is named after Franklin, New Jersey, U.S., the site of its occurrence as the dominant ore mineral for zinc (Zn); and sillimanite (Al2SiO4) is in honour of the American chemist Benjamin Silliman. Since 1960 the Commission on New Minerals and Mineral Names of the International Mineralogical Association has reviewed descriptions of new minerals and proposals for new mineral names and has attempted to remove inconsistencies. Any new mineral name must be approved by this committee, and the type material is usually stored in a museum or university collection.

franklinite, willemite, and calciteSpecimen showing bright fluorescent colour resulting from ultraviolet irradiation of calcite (calcium carbonate; red fluorescence) with grains of franklinite (a zinc, manganese, and iron oxide; black coloration), which is nonfluorescent. Veins and grains of willemite (a zinc silicate; green fluorescence) also appear.Benjamin M. Shaub