Wednesday, July 18, 2007

Chem (history and branches)

History of Chemistry

1. PRACTICAL ARTS (-- to 600 BC)
· Inhabitants of Ancient Egypt and Mesopotamia
· Crafts: production of metals, pottery, brewing, baking, production of dyes
· Development was based on everyday experiences
· No reference to chemical principles

2. GREEK THEORY (600 BC- 300 BC)
· Greeks wanted to understand nature
· 1st theory- Substances are composed of 4 elements – Earth, Air, Fire Water
· 2nd theory- Matter = ATOMS by Leucippus and Democritus
· TRANSMUTATION- transformation of one element into another
· PLATO- transmutation is achieved by changing the shape of the atoms
· ARISTOTLE- elements and substances are made up of PRIMARY MATTER. Transformation is achieved when the form (shape, color etc.) is altered

3. ALCHEMY ( 300 BC- 1650 AD)
· Combination of ideas from the ancient Greeks and Egyptians
· Laboratory Apparatus (crucible)
· Laboratory Methods (crystallization, distillation and sublimation)
· Philosopher’s Stone (changes metals into gold)
· Elixir of Life (was believed to cure diseases; promote immortality of humans)
· IATROCHEMISTRY- branch of alchemy concerned with medicine
· ROBERT BOYLE- believed that metals can be changed into gold but this theory should be based on EXPERIMENTAL evidence.

4. PHLOGISTON THEORY (1650-1790)
· Work of Georg Ernst Stahl
· Was later found to be erroneous
· “Phlogiston” – a substance present in all flammable objects; is released when the object is burned
· “Calx”- powdery residue after burning of a substance

5. MODERN CHEMISTRY (1790 to 1999)
· Antoine Lavoisier marks the beginning of modern chemistry.
· Relied on the results of quantitative experimentation to explain certain phenomena
· Law of Conservation of Mass – Mass Before reaction = Mass After Reaction
· Wrote and Published à Elementary Treatise on Chemistry à the language of chemistry today


Branches of Chemistry

1. Organic Chemistry
* concerned with elements containing carbon (all living organisms contain at least some amount of carbon in their body)
* pharmaceutical, petrochemical and textile industries

2. Inorganic Chemistry
* concerned with elements not containing carbon (minerals of the earth’s crust and non-living matter)
* nuclear science and energy, geochemistry

3. Physical Chemistry
* behavior of chemical substances
* deals with the relations between physical properties of substances and their chemical formations along with their changes

4. Biochemistry
* concerned with the composition and changes in the formation of living species
* also called physiological chemistry or biological chemistry
* study the property of molecules, metabolism, vitamins etc.

5. Analytical Chemistry
*deals with the composition of substances* e.g. nicotine content of cigarettes and sugar content of carbonated drinks

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