Химия. Экология. Медицина



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LITHIUM

Afua Gyaa Asibey, group 25. Science adviser is Olga Levashova.


Lithium is a word which was obtained from the Greek word Lithos, stone. it is a chemical with the symbol Li. it has an atomic number of 3. it is soft, silver-white metal belonging to the alkaline metal group of elements. Petalite [LiAlSi4O3] was the first Lithium compound to be discovered in 1800 by a Brazillian chemist Jose Bonifacio de Andrada the Silva in a mine on the island of Uto in Sweden. However, in 1817, John August Artwedson detected the presence of a new element while analysing petalite ore. This element formed compounds similar to those of Sodium and Potassium though its carbonates and hydroxide were less soluble in water and more alkaline. Artwedson later showed that this same element was present in the minerals Spodumen and Lepidolite. However, in 1821, William Thomas was the first to isolate Lithium. He did this through electrolysis of LithiumOxide. He described some pure salts of Lithium such as Chloride. In 1855, larger quantities of Lithium were produced through electrolysis of LithiumChloride.

Under standard conditions, it is the lightest metal and the least dense solid element. Like all metals, Lithium is highly reactive and flammable. For this reason, it is typically stored in mineral oil. When cut open, Lithium exhibits a metallic lustre. But contact with moist air corrodes the surface quickly to a dull silvery grey then a black tarnish called Lithium Hydroxide. Because of its high reactivity, Lithium never occurs freely in nature and instead only appears in compounds which are usually ionic. Lithium occurs in the number of pegmatic minrals but due to its solubility as an ion. It is present in ocean water and is commonly obtained from brines and clays. On a commercial scale, Lithium is isolated electronically from a mixture of Lithium Chloride and Potassium Chloride.

Lithium has a very low melting point of 180oC. It has the lowest melting point compared to all other metals. Lithium has a very low density of 0.534g/cm3. Lithium's co-efficient of thermal expansion is twice that of Aluminium and almost four times that of Iron. It has the highest specific heat capacity of 3.58 KJ/Kg/K. Due to its highest specific heat capacity, Lithium metal is often used in coolants for heat transfer application. Lithium reacts easily with water to form Hydrogen gas and Lithium Hydroxide in aqueous solution. When placed over flame, Lithium compounds give off a striking crimson colour but when it burns strongly, the flame becomes a brilliant silver colour. Lithium is a microelement (10-4%). The nuclei of Lithium verge on instablity since the two stable Lithium isotopes: Li6 and Li7 found in nature have the lowest binding energies per nucleon of all stable nuclides. Because of its relative nuclear instability, Lithium is less common in the solar system than twenty five of the first thirty two chemical elements. Eventhough the nuclei are very light in atomic weight, for related reasons Lithium has important links to Nuclear Physics. The transmutation of Lithium atoms to Helium in 1932 was the first fully man-made nuclear reactions and Lithium-6 serves as fission fuel in staged thermonuclear weapons.

It is included in the composition of blood,tissues and organs of human and animals.Especiallythere is a lot of li in the muscles.Lithium being antagonist of sodium and potassium displaces them out of tissues when gets into the organism.Lithium ions influences the transport of sodium ions in neurons and myocytes.Lithium ions take part in regulation of higher nervous activity and also affects immunity and water-salt metabolism.Lithium salts possess antistress action-they supress pathological lability and exaltation agression at mental diseases.

Higher concentration of lithium in hair may be detected in patients with disturbances of kidney's excretive functions.lithium is detected in patients with psychic disorders ,kidney diseases as well as inn offspring of dipsomaniacs ,in patients with immune deficiency diseases including neoplesm risk.

MINERALS ARE EARTH’S TREASURE

Adil Mohammed Shahab, group 25. Science adviser is Olga Levashova.


The meaning of the word “treasure” could be stated as highly debatable and controversial. Although, it could be summed down to an object which could be regarded as very valuable and tempting. But I’d like to present a mineral, which we almost ignore regularly and do not acknowledge thanks to its abundance … the limestone calcite.

Calcite (CaCO3):

This mineral is most commonly and abundantly formed and found as result of simultaneous buildup of tiny calcite plates which are shed by micro-organisms known as coccolithophores under deep but not unreachable marine conditions.

Composition:

Chalk is composed mostly of calcium carbonate with minor amounts of silt and clay. It is normally formed underwater, then consolidated and compressed during digenesis into the form commonly seen today.

Fascinating properties and uses:

Contrary to its fragile look, chalk actually is in fact remarkably resistant to weathering. It is also very impressive job when coming to storing groundwater, acting as a reservoir and releasing it during drier eras due to its phenomenal porous nature. These specific traits are the reason why we may observe “chalk hills”, or more scientifically called “chalk download”. Furthermore, due to its porosity it has been also become centre of attraction in geophysical experiments. It also been used in “evaluating 4D seismic for the correct pore pressure prediction”. Most importantly, it is used in schools and universities to bloom the creative minds of students with the guidance of brilliant teachers. Hence, resulting in the graduation of potential professors, doctors, scientists who’d find more about chalks...probably, and what not. Not to forget economical & social growth as a consequential.

Probably the primary educations of scientists who have worked on finding about Calcite were guided by a chalk piece resulting in one of the biggest revolution in the world.

And so, I believe calcite is worth regarding it to as Earth’s treasure.

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