Chemical elements may also be categorized by their origin on Earth, with the first 98 considered to be naturally occurring, while those with atomic numbers beyond 98 have only been produced artificially as the synthetic products of man-made nuclear reactions.

Chemical thermodynamics is the study of the interrelation of heat and work with chemical reactions or with physical changes of state within the confines of the laws of thermodynamics.

# Chemical reactions

Chemical reactions are usually characterized by a chemical change, and they yield one or more products, which usually have properties different from the reactants.

Chemical reactions are described with chemical equations, which graphically present the starting materials, end products, and sometimes intermediate products and reaction conditions.

Chemical reactions happen at a characteristic reaction rate at a given temperature and chemical concentration, and rapid reactions are often described as spontaneous, requiring no input of extra energy other than thermal energy.

Chemical reactions such as combustion in the fire, fermentation and the reduction of ores to metals were known since antiquity.

Chemical equations are used to graphically illustrate chemical reactions.

Chemical reactions are determined by the laws of thermodynamics.

" Chemical affinity ", historically, refers to the " force " that causes chemical reactions.

Chemical exothermic reactions are generally more spontaneous than their counterparts, endothermic reactions.

Chemical endothermic reactions need heat to be performed.

Category: Chemical reactions

Chemical chain reactions were first proposed by German chemist Max Bodenstein in 1913, and were reasonably well understood before nuclear chain reactions were proposed.

Chemical reactions, as macroscopic unit operations, consist of simply a very large number of elementary reactions, where a single molecule reacts with another molecule.

Chemical thermodynamics studies the role of entropy in chemical reactions.

Chemical reactions cause nitrogen and oxygen to be removed from the bubble after about one hundred expansion-collapse cycles.

* Chemical Equation Balancer-An open source chemical equation balancer that handles redox reactions.

Category: Chemical reactions

Chemical weathering changes the composition of rocks, often transforming them when water interacts with minerals to create various chemical reactions.

Chemical rockets are the most common type of rocket and they typically create their exhaust by the combustion of rocket propellant.

The words, with some variations, are used in the track Jerusalem on Bruce Dickinson's album The Chemical Wedding, which also includes lines from book two of Milton.

The US military has specialized units, which can respond to a bioterrorism event ; among them are the US Marine Corp's Chemical Biological Incident Response Force and the U. S. Army's 20th Support Command ( CBRNE ), which can detect, identify, and neutralize threats, and decontaminate victims exposed to bioterror agents.

Chemical substances are classified in terms of their structure, phase, as well as their chemical compositions.

Other fields where chemical degrees are useful include Astrochemistry ( and Cosmochemistry ), Atmospheric chemistry, Chemical Engineering, Chemo-informatics, Electrochemistry, Environmental science, Forensic science, Geochemistry, Green chemistry, History of chemistry, Materials science, Medical science, Molecular Biology, Molecular genetics, Nanotechnology, Nuclear chemistry, Oenology, Organometallic chemistry, Petrochemistry, Pharmacology, Photochemistry, Phytochemistry, Polymer chemistry, Supramolecular chemistry and Surface chemistry.

Chemical element symbols are always capitalized ( see below ).

Chemical symbols are understood internationally when element names might need to be translated.

The most popular options are Chemical Engineering, Computer Science, Electrical Engineering, Mechanical Engineering and Physics.

The most popular options are Chemistry, Physics, Biology, Electrical Engineering and Chemical Engineering.

Chemical species that improve catalytic activity are called co-catalysts ( cocatalysts ) or promotors in cooperative catalysis.

# Azo dye CD-Rs are dark blue in color, and their formulation is patented by Mitsubishi Chemical Corporation.

Chemical gradients are sensed through multiple transmembrane receptors, called methyl-accepting chemotaxis proteins ( MCPs ), which vary in the molecules that they detect.

The atoms in the structure are colour coded by Chemical element | element and the detailed structure of two base pairs are shown in the bottom right. The structure of part of a DNA double helix

The United States Food and Drug Administration lists these items as " Generally recognized as safe " or GRAS ; they are listed under both their Chemical Abstract Services number and Fukda regulation under the US Code of Federal Regulations.

However, recent research published in Environmental Science & Technology, a publication of the American Chemical Society, suggests that many cases of feline hyperthyroidism are associated with exposure to environmental contaminants called polybrominated diphenyl ethers ( PBDEs ), which are present in flame retardants in many household products, in particular, furniture and some electronic products.

The American Institute of Chemical Engineers ( AIChE ), established in 1908, played a key role in making chemical engineering considered an independent science, and unit operations central to chemical engineering.

# Chemical stability: CSF flows throughout the inner ventricular system in the brain and is absorbed back into the bloodstream, rinsing the metabolic waste from the central nervous system through the blood – brain barrier.

At the end of and first year after World War II the Academy consisted of eight divisions ( Physico-Mathematical Science, Chemical Sciences, Geological-Geographical Sciences, Biological Science, Technical Science, History and Philosophy, Economics and Law, Literature and Languages ); three committees ( one for coordinating the scientific work of the Academies of the Republics, one for scientific and technical propaganda, and one for editorial and publications ), two commissions ( for publishing popular scientific literature, and for museums and archives ), a laboratory for scientific photography and cinematography and Academy of Science Press departments external to the divisions ; 7 filials ( Azerbaijan, Kazakhstan, Kirghizia, Tadzhikistan, Turkmenistan, Urals, and West Siberian ), and 8 independent of central Academies in Ukraine, Belorussia, Armenia, Georgia, Lithuania, Uzbekistan, Latvia, and Estonia.

MILES 2 was released in 1991-92, and the SAWE ( Simulated Area Weapons Effects ) add-on was first fielded in 1992 using GPS and RF messages so that vehicles and individual soldiers can be killed from a central location due to artillery strikes, or Nuclear, Biological, and Chemical weapons strikes.

* Chemical stratigraphy of the lunar crust by remote sensing of the central uplands of large lunar craters, and of the South Pole Aitken Region ( SPAR ), an expected site of interior material

The Newport Chemical Depot, previously known as the Wabash River Ordnance Works and the Newport Army Ammunition Plant, was a bulk chemical storage and destruction facility in west central Indiana, thirty miles north of Terre Haute operated by the United States Army.