Phase2

The first metal was worked copper. In fact, copper was then considered as a type of bronze. Indeed, the word "copper" etymologically means "bronze of Cyprus" to where the early careers were created copper in antiquity and the end of prehistory. The men began work probably native copper (that is to say, this naturally as a metal) by hammering, and they realized it was probably easier to work when it was heated (the phenomenon of annealing: the elimination of dislocations by the restructuring and possible recrystallization). Then, warming increasingly, they realized that he founded and that it therefore could be molded. This is the Copper Age, around -4000. The first was a bronze alloy (copper and tin). The bronze age spread of about -2500 to -1000 although it was thought that copper was a type of bronze. Native copper is rare, then they worked ores poorer native copper, and they probably noticed that the heat makes it possible not only minerals to extract copper by fusion, but also to "transform "Metal ore (reduction), which is probably were born and low ranges, around -1200. -1000 To the Iron Age began. Iron melts at much higher temperature than copper (1535 ° C against 1084 ° C), reducing the ore in the furnace bottom was flawed and gave birth to a block of sponge-like appearance (the mass or the magnifying glass) we hammered it to remove impurities. The first to use iron were the Hittites. In Africa, about -2000 Nok civilization developed early this science from the stone age directly to the Iron Age. Throughout the rest of antiquity only a few metals were used and only worked for some. Were known only seven metals: gold, mercury, lead, silver, iron, copper and tin. It was not until 1750, when the discovery of bismuth to attend the discovery of a new metal and 1735 to discover cobalt. = The chemical Formula: = The structure of wood is H3OC : = = The structure of alluminuim is Al : = Al = The structure of Iron is Fe : = Fe = The structure of Copper is Cu : = Cu = The structure of Steel is FeC : = FeC =
 * The materials :**

By Mehdi

Price, environment, and the future
=== The biggest threat to the conventional plastics industry is most likely to be environmental concerns, including the release of toxic pollutants, greenhouse gas, litter, biodegradable and non-biodegradable landfill impact as a result of the production and disposal of petroleum and petroleum-based plastics. Of particular concern has been the recent accumulation of enormous quantities of plastic trash in ocean gyres. ===

.. A major cause is the sharply rising cost of petroleum, the raw material that is chemically altered to form commercial plastics.
=== With some observers suggesting that future oil reserves are uncertain, the price of petroleum may increase further. Therefore, alternatives are being sought. Oil shale and tar oil are alternatives for plastic production but are expensive. Scientists are seeking cheaper and better alternatives to petroleum-based plastics, and many candidates are in laboratories all over the world. One promising alternative may be fructose. === = BY MEHDI =

**// A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, and other covalent bonds. In short, the stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding. //**

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 * // Covalent bonding includes many kinds of interaction, including σ-bonding, π-bonding, metal to metal bonding, agnostic interactions, and three-center two-electron bonds The term covalent bond dates from 1939,The prefix co- means jointly, associated in action, partnered to a lesser degree, etc. thus a "co-valet bond", essentially, means that the atoms share "valence", such as is discussed in valence bond theory. In the molecule H2, the hydrogen atoms share the two electrons via covalent bonding. Covalence is greatest between atoms of similar electro negativities. Thus, covalent bonding does not necessarily require the two atoms be of the same elements, only that they are of comparable electro negativity. //**=====

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 * // Although covalent bonding entails sharing of electrons, it is not necessarily delocalized. Furthermore, in contrast to electrostatic interactions ("ionic bonds") the strength of covalent bond depends on the angular relation . //**=====

**//BY AHMAD ASHA//**

properties of steel

The use of stainless steel gives engineers extra flexibility in their design due to its excellent corrosion resistance, weight to strength and fabrication properties. If the seat is made of iron will carry heavy weights and also do not break the fast

By abdullah

//** Steel has a lot of great characteristics. With steel you don’t need to worry about rot, termites, mold or carpenter ants. And it won’t warp with age or changing moisture levels. Steel is also fire resistant. It won’t burn but steel can melt (approximately 785° F according. **//

//** Advantage: **//

//** 1) You don’t have to worry about rot, and termites mold or carpenter ants. **// //** 2) It won’t get deformed with age or moisture levels. **// //** 3) Steel is also fire resistant, it won’t burn. **//

//** The bad things about the wood: **// //** 1) The rot, and termites mold or carpenter ants can eat the chairs made of wood. **// //** 2) It cant get deformed with age or levels. **// //** 3) Wood is not fire resistant it can burn. **//

**// BY AHMAD. //**

//** What are the properties of covalent compounds? **//


 * 1) As you may recall, ionic compounds have very high melting and boiling points because it takes a lot of energy for all of the + and - charges which make up the crystal to get pulled apart from each other. Essentially, when we have an ionic compound, we need to break all of the ionic bonds in order to make it melt. **


 * 2) The reason for this is similar to the reason that covalent compounds have low melting and boiling points. When you hit an ionic compound with something, it feels very hard. The reason for this is that all of the ionic bonds, which hold together the crystal, tend to make it very inflexible and hard to move. On the other hand, covalent compounds have these molecules, which can very easily move around each other, because there are no bonds between them. As a result, covalent compounds are frequently flexible rather than hard. **

**3) The main reason that things burn is because they contain carbon and hydrogen atoms that can react to form carbon dioxide and water when heated with oxygen gas (that's the definition of a combustion reaction). Since carbon and hydrogen have very similar electro negativities, they are mostly found together in covalent compounds. As a result, more covalent compounds than ionic compounds are flammable.**

**4) Electricity is conducted in water from the movement of ions from one place to the other. These ions are the charge carriers, which allow water to conduct electricity. Since there are no ions in a covalent compound, they don't conduct electricity in water.**


 * 5) There's a saying that, "Like dissolves like". This means that compounds tend to dissolve in other compounds that have similar properties (particularly polarity). Since water is a polar solvent and most covalent compounds are fairly no polar, many covalent compounds don't dissolve in water. Of course, this is a generalization and not set in stone - there are many covalent compounds that dissolve quite well in water. However, the majority of them don't because of this rule. **

**// BY ABDULLAH ASHGAR //**