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ChemistryChemistry is the study of structure, properties, composition, and transformation of substances. Chemistry deals with chemical elements and compounds, which consist of atoms and molecules, and the reactions between them. See also: the periodic table and list of compounds. Table of contents showTocToggle("show","hide") 1 Overview 2 Branches of chemistry 3 Chemicals and interactions 4 Quantitative chemistry 5 States of matter 6 Acids and bases 7 Kinetics and thermodynamics 8 History of chemistry 9 Etymology 10 See also 11 External links Overview The atomic theory is basic to chemistry. The theory states that all matter is composed of a set of very small units called atoms. One of the very first laws to be discovered leading to the establishment of chemistry as a science is the Law of Conservation of Mass. This law states there is no detectable change in the quantity of matter during an ordinary chemical reaction. (Modern physics now shows that it is actually energy that is conserved, and that energy and mass are related) On a superficial level this means that if we start off with 10,000 atoms and proceed with many chemical reactions, we will still be left with exactly 10,000 atoms. The mass will be the same too if the energy gained or lost is accounted for. Chemistry studies the interactions of these atoms, sometimes alone but more often combined with (bonded to) other atoms to form ions and compounds/molecules. These atoms interact with other atoms (e.g., a wood fire is the combination of oxygen atoms from the air with the carbon and hydrogen atoms in the wood) and they may also interact with light (a photograph is formed from the changes that light causes to the chemicals on a film) and other types of radiation. One surprisingly early finding was that these atoms almost always combine in definite ratios or proportions: silica sand is a structure where the ratio of silicon atoms to oxygen atoms is 1:2. We now know that there are exceptions to this law of definite proportions (integrated circuits are a good example). Another key discovery in chemistry was that when a specific chemical reaction occurs, the amount of energy gained or lost will always be the same. This leads to the important concepts of equilibrium, thermodynamics, and kinetics. Physical chemistry is grounded upon modern physics, and it is in principle possible to describe all chemical systems using the theory of quantum mechanics. This theory is mathematically complex and profoundly non-intuitive. In practice, however, only the simplest chemical systems may realistically be investigated in purely quantum mechanical terms, and approximations must be made for most practical purposes (e.g. Density functional theory). Hence a detailed understanding of quantum mechanics is not necessary for most chemistry, as the important implications of the theory (principally the orbital approximation) can be understood and applied in simpler terms. Although quantum mechanics may frequently be ignored, the fundamental concept behind it - quantisation of energy - may not. Chemists depend on quantum effects for - amongst other things - all spectroscopic techniques, although many may not realise it! Again, frequently the physics may be ignored, and the end result (e.g. an NMR Spectrum) interpreted nonetheless. A full physical description of chemistry must also take into account relativity, the other principle theory of modern physics, also mathematically complex. Fortunately, relativistic effects are only important in extremely precise calculations of atomic structure, mainly involving the heavier elements, and relativity is in practice irrelevant to almost all chemistry. Chemistry typically is divided into following major parts: analytical chemistry, the determination of substance composition and its constituents; organic chemistry, the study of carbon compounds; inorganic chemistry, dealing with broader elements not emphasized in organic chemistry; biochemistry, the study of chemistry in biological system; and physical chemistry, which forms the foundation of all other branches, encompassing the physical property of substances and the theoretical tools to investigate them. Other cross-disciplinary studies and specialization branches include: materials science, polymer chemistry, environmental chemistry, Pharmacy
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Houk Kaplan SAT II: Chemistry 2004-2005 by Kaplan Uncle Tungsten : Memories of a Chemical Boyhood by Oliver Sacks Recent Chemistry related patents From USPTO: 6714877: Method for correcting combustion effluent data when used for input-loss performance monitoring of a power plant 6714875: Method for producing and screening mass-coded combinatorial libraries for drug discovery and target validation 6714815: Method for the iontophoretic non-invasive determination of the in vivo concentration level of an inorganic or organic substance 6714736: System and method for communication of digital images generated from photographic film 6714712: Radiation curable coating composition 6714675: Autogrid analysis 6714618: Temperature-based method for controlling the amount of metal applied to metal oxide surfaces to reduce corrosion and stress corrosion cracking 6714412: Scalable coolant conditioning unit with integral plate heat exchanger/expansion tank and method of use 6714402: Microfabricated electrochemical device separators 6714296: Method and apparatus for inspecting photosensitive material for surface defects 6714287: Apparatus for determining the volume of single red blood cells 6714033: Probe for direct wafer potential measurements 6713969: Method and apparatus for determination and control of plasma state 6713955: Organic light emitting device having a current self-limiting structure 6713842: Mask for and method of forming a character on a substrate 6713785: Thin film transistor and display device having the same 6713781: Organic light-emitting device having phenanthroline-fused phenazine 6713774: Structure and method for controlling the thermal emissivity of a radiating object 6713772: Free-form fabrication using multi-photon excitation 6713762: Acoustic absorption electromagnetic radiation sensing with SIC 6713757: Controlling the temporal response of mass spectrometers for mass spectrometry 6713739: Microwave-assisted chemical synthesis instrument with fixed tuning 6713738: Methods for temperature control in microwave processing 6713671: Magnetically shielded assembly 6713665: Maize NPR1 promoter and methods of use in plant gene expression 6713656: Preparation of diacetals of glyoxal 6713655: Integrated process for synthesizing alcohols, ethers, aldehydes, and olefins from alkanes 6713654: Antimicrobial compounds 6713651: .beta.2-adrenergic receptor agonists 6713650: ABCA-1 elevating compounds 6713647: Compounds having activity as inhibitors of cytochrome P450RAI 6713646: Degradable crosslinkers, and degradable crosslinked hydrogels comprising them 6713645: Substituted tricyclics 6713644: Hydrosilation with platinum free neat copper containing catalyst 6713642: Method for producing alkali metal monohydridoborates and monohydridoaluminates 6713641: Reactive anthraquinone colorant compounds and polymeric materials reacted therewith 6713639: Process for preparing enantiomerically pure (S)-3-hydroxy-gamma-butyrolactone 6713638: 2-amino-3-aroyl-4,5 alkylthiophenes: agonist allosteric enhancers at human A1 adenosine receptors 6713637: Process for preparing a 2-hydroxymethyl-2,3-dihydro-thieno[3,4-b][1,4] dioxine-5,7-dicarboxylic acid diester 6713635: 2-oxo-1-pyrrolidine derivatives, process for preparing them and their uses 6713632: Process for the preparation of imidazole derivatives 6713631: Preparation method of 2,2'-bi-1H-imidazole using glyoxal and an ammonium salt 6713630: Continuous preparation of substituted oxazoles 6713627: Processes for the preparation of (R)-.alpha.-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl)ethyl]-4-piperidine methanol 6713626: Process for synthesizing N-aryl piperazines with chiral N'-1-[benzoyl(2-pyridyl)amino]-2-propane substitution 6713622: 4,7-dichlororhodamine dye labeled polynucleotides 6713621: Chimeric oligonucleotides for modulating gene expression 6713619: Oncogenes and methods for their detection 6713616: High affinity TGF.beta. nucleic acid ligands and inhibitors |