Metal - online puzzles

Metal

A metal (from Ancient Greek μέταλλον métallon 'mine, quarry, metal') is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typically ductile (can be drawn into wires) and malleable (they can be hammered into thin sheets). These properties are the result of the metallic bond between the atoms or molecules of the metal.

A metal may be a chemical element such as iron; an alloy such as stainless steel; or a molecular compound such as polymeric sulfur nitride.In physics, a metal is generally regarded as any substance capable of conducting electricity at a temperature of absolute zero. Many elements and compounds that are not normally classified as metals become metallic under high pressures. For example, the nonmetal iodine gradually becomes a metal at a pressure of between 40 and 170 thousand times atmospheric pressure. Equally, some materials regarded as metals can become nonmetals. Sodium, for example, becomes a nonmetal at pressure of just under two million times atmospheric pressure.

In chemistry, two elements that would otherwise qualify (in physics) as brittle metals—arsenic and antimony—are commonly instead recognised as metalloids due to their chemistry (predominantly non-metallic for arsenic, and balanced between metallicity and nonmetallicity for antimony). Around 95 of the 118 elements in the periodic table are metals (or are likely to be such). The number is inexact as the boundaries between metals, nonmetals, and metalloids fluctuate slightly due to a lack of universally accepted definitions of the categories involved.

In astrophysics the term "metal" is cast more widely to refer to all chemical elements in a star that are heavier than helium, and not just traditional metals. In this sense the first four "metals" collecting in stellar cores through nucleosynthesis are carbon, nitrogen, oxygen, and neon, all of which are strictly non-metals in chemistry. A star fuses lighter atoms, mostly hydrogen and helium, into heavier atoms over its lifetime. Used in that sense, the metallicity of an astronomical object is the proportion of its matter made up of the heavier chemical elements.Metals, as chemical elements, comprise 25% of the Earth's crust and are present in many aspects of modern life. The strength and resilience of some metals has led to their frequent use in, for example, high-rise building and bridge construction, as well as most vehicles, many home appliances, tools, pipes, and railroad tracks. Precious metals were historically used as coinage, but in the modern era, coinage metals have extended to at least 23 of the chemical elements.The history of refined metals is thought to begin with the use of copper about 11,000 years ago. Gold, silver, iron (as meteoric iron), lead, and brass were likewise in use before the first known appearance of bronze in the fifth millennium BCE. Subsequent developments include the production of early forms of steel; the discovery of sodium—the first light metal—in 1809; the rise of modern alloy steels; and, since the end of World War II, the development of more sophisticated alloys.

Old Buttons puzzle online from photoMozart Statue in Salzburg (Austria) online puzzlePolish zloty puzzle online from photoClocks puzzle online from photoInside of the lighthouse on the Island of Vierge (France) online puzzlePearls online puzzleChocolate products arranged in rows puzzle online from photoMillennium Bridge (United Kingdom) online puzzleNew Year’s composition with old clock online puzzleChocolates online puzzleChristmas gingerbread online puzzleWindmill on the graduation tower (Poland) puzzle online from photoEiffel Tower (France) puzzle online from photoHistoric opera glasses online puzzlePolished pieces of glass online puzzleRed-footed Booby puzzle online from photoDollars and euros puzzle online from photoBeelitz Heilstätten (Germany) puzzle online from photoJewelry online puzzleKlocka online puzzlecoats of arms puzzle online from photoKeys puzzle online from photoJohann Strauss Monument in Vienna (Austria) online puzzleArab tea with dried dates puzzle online from photo
Tools of the past puzzle online from photoPaint cans online puzzleCollection of old suitcases online puzzleBridge between Frederiksø and Christiansø (Denmark) puzzle online from photoHistoric district in Galveston (USA) puzzle online from photoCorks online puzzleOld compass lying on dollar bills online puzzleStreet lamp puzzle online from photoEngine puzzle online from photoNavajo Bridge (USA) puzzle online from photoRound... online puzzleAlarm clocks online puzzleOld black telephone with a dial puzzle online from photoColored nail polish on a pink background online puzzleEngine online puzzleClocks online puzzleTrain at the train station in Kalmar (Sweden) puzzle online from photoAn assortment of spieces puzzle online from photoPralines puzzle online from photobuttons online puzzleLeather handbags puzzle online from photovintage brooches online puzzleThumbtacks puzzle online from photoPrague Astronomical Clock online puzzle