Химия. Экология. Медицина



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MINERALS ARE EARTH'S TREASURES

Khalil Al Jaddouh, group 3. Science adviser is Svetlana Kozub.


Definition: Minerals are natural compounds formed through geological processes. A mineral is a naturally occurring, inorganic solid with a definite chemical composition and a crystalline structure There is an overwhelming number of known minerals. Currently, the International Mineralogical Association lists more than 4,600 minerals with new minerals still being discovered. Only 100 of these are common, while the rest are either encountered occasionally, or are very rare. With such a large number of minerals, it is difficult to identify and classify them separately.

The most commonly found group of minerals in the Earth's crust is the silicate group. Almost all silicate minerals have silicon and oxygen as their base units. Most silicate minerals are formed by the cooling of molten rocks. As the molten rocks come closer to the surface inside the Earth's crust, they start cooling very fast and combine with the most abundant element in the Earth's crust -- silicon. Silicate minerals constitute approximately 90% of the Earth's crust. Mica, quartz, amazonites, olivine, and biotite are some of the examples of silicate minerals.

Non-silicateMinerals

There is a complete range of non-silicate minerals. Some of these are formed when there is cooling of magma, while some others are formed when water in them evaporates, or due to mineral decomposition. The non-silicates can be further classified into different groups which are:

Native Elements: Many pure elements that are found with a distinct mineral structure and occur naturally in an uncombined form, fall under this category. For example: uncombined carbon is often found in its pure state in the form of graphite or more rarely as diamond. Gold, silver, and sulfur are other elements, which are also found in their pure state. Even though these are pure elements, they qualify to be known as minerals, but no chemical process is required on them further.

Sulfides: This class of minerals have sulfide (S2−) as their basic unit. These inorganic compounds are sometimes as economically important as other ores. Some examples include Nickeline (NiAs), Pyrite (FeS2) and Molybdenite (MoS2).

Oxides: When an ore is found in which one or more elements are combined with oxygen, it is an oxide mineral. These may have chemical formulas of the type XO (MgO, ZnO, CuO, etc.), X2O (Cu2O), X2O3 (Al2O3, Fe2O3), XO2 (MnO2, SnO2) and XY2O4 (MgAl2O4, FeCr2O4). The oxide minerals are mostly of metallic elements. Example: hematite, magnetite, and cuprite. Silicates and oxides are the most common types of minerals in volcanoes, especially after an eruption.

Carbonates: This particular type is formed when a single carbonate ion (CO32-) reacts with a metal ion of complementing polarity. Example: siderite (FeCO3), smithsonite (ZnCO3), calcite (CaCO3). Carbonate minerals are used in making cement and other bonding material.

Sulfates: The mineral class which includes the sulfate ion (SO42-) within its molecular structure is categorized as a sulfate mineral. Minerals like Gypsum (CaSO4•2H2O) and Barite (BaSO4) are examples of sulfate minerals.

Organic Minerals: This class of minerals includes biogenic substances, genesis, or origin of which can be attributed to a geological process. Organic minerals include all types of oxalates, mellitates, citrates, cyanates, acetates, formates, hydrocarbons, etc. Examples of organic minerals include whewellite, moolooite, mellite, fichtelite, carpathite, evenkite, and abelsonite.

Apart from these, there are many more non-silicate minerals, like nitrates, sulfides, halides, phosphates, etc., but most of the 4,000-odd listed minerals are grouped in the above categories. Make sure you do not get confused between minerals and rocks. A rock is a combination of a number of minerals, which may also include organic remains and mineraloids, i.e., non-crystalline minerals.

REACTION IN CHEMISTRY

Jad Ahmad, group 3. Science adviser is Svetlana Kozub.


Defintion: A chemical reaction is a process that leads to the transformation of one set of chemical substances to another.

• Types of chemical reaction:

1-Decomposition reaction

A decomposition reaction is the opposite of a synthesis reaction, where a more complex substance breaks down into its more simple parts. These reactions are in the general form

One example of a decomposition reaction is the electrolysis of water to make oxygen and hydrogen gas

2-Single replacement:

In a single replacement reaction, a single uncombined element replaces another in a compound; in order words, one element trades places with another element in a compound.

One example of a single displacement reaction is when magnesium replaces hydrogen in water to make magnesium hydroxide and hydrogen gas.

3-Double replacement:

In a double replacement reaction, the anions and cations of two compounds switch places and form two entirely different compounds. These reactions are in the general form.

For example, when barium chloride (BaCl2) and magnesium sulfate (MgSO4) react, the SO42- anion switches places with the 2Cl- anion, giving the compounds BaSO4 and MgCl2.

Another example of a double displacement reaction is the reaction of lead(II) nitrate with potassium iodide to form lead(II) iodide and potassium nitrate

Representation of four basic chemical reactions types: synthesis, decomposition, single and double replecment.

4-Acid-base reactions:

An acid-base reaction involves a transfer of protons (H+) from one species (the acid) to another (thebase).

HA: acid, B: Base, A−: conjugated base, HB+: conjugated acid

5-Oxidation and reduction:

Redox reactions can be understood in terms of transfer of electrons from one involved species (reducing agent) to another (oxidizing agent).

In the following redox reaction, hazardous sodium metal reacts with toxic chlorine gas to form the ionic compound sodium chloride, or common table salt.

6-Combustion reaction:

Combustion reactions always involve molecular oxygen O2. Anytime anything burns (in the usual sense), it is a combustion reaction. Combustion reactions are almost always exothermic (i.e., they give off heat). For example when wood burns, it must do so in the presence of O2 and a lot of heat is produced.

7-Solid-state reactions

Reactions can take place between two solids. However, because of the relatively small diffusion rates in solids, the corresponding chemical reactions are very slow in comparison to liquid and gas phase reactions. They are accelerated by increasing the reaction temperature and finely dividing the reactant to increase the contacting surface area.

8-Organic reactions.

are chemical reactions involving organic compounds.[1] The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, photochemical reactions and redox reactions. In organic synthesis, organic reactions are used in the construction of new organic molecules. The production of many man-made chemicals such as drugs, plastics, food additives, fabrics depend on organic reactions.

The oldest organic reactions are combustion of organic fuels and saponification of fats to make soap. Modern organic chemistry starts with the Wöhler synthesis in 1828. In the history of the Nobel Prize in Chemistry awards have been given for the invention of specific organic reactions such as the Grignard reaction in 1912, the Diels-Alder reaction in 1950, the Wittig reaction in 1979 and olefin metathesis in 2005.

Finally…This are not all the type in chemical reaction but this is the most reaction we are incontect in chemistry lessons.

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