Chemistry is the science that studies the composition, structure and properties of matter and the changes it undergoes during chemical reactions and their relationship with energy. Linus Pauling defined it as the science that studies substances, their structure (types and forms of arrangement of the atoms), their properties and reactions that transform them in other substances in reference with the time.
Modern chemistry developed out of alchemy, a practice proto of philosophical character, which combined elements of chemistry, metallurgy, physics, medicine, biology, among other sciences and arts. This phase ends upon the occurrence of the call Revolution of the chemical, based on the law of conservation of matter and the theory of combustion oxygen was postulated by the French scientist Antoine Lavoisier.
The disciplines of chemistry are grouped according to the class of matter under study or the type of study undertaken. Among these are the inorganic chemistry, which studies the inorganic matter; organic chemistry, which studies organic matter; biochemistry, which studies the substances existing in biological organisms; physical chemistry, which includes the energy aspects of chemical systems at multiple scales (macroscopic, molecular and atomic physics, and analytical chemistry, which analyzes samples of matter and try to understand its composition and structure through various studies and reactions.
Chemistry covers a field of studies quite broad, so that, in practice, we study each topic in a particular way. The six major and most studied branches of chemistry are:
Inorganic chemistry: synthesis and study of the properties of electrical, magnetic and optical compounds formed by atoms that are not carbon (though with some exceptions). Is especially novel compounds with transition metals, acids and bases, among other compounds.
Organic chemistry: Synthesis and study of compounds based on carbon chains.
Biochemistry: study the chemical reactions in living beings, studying the body and living beings. Biochemistry is the study of the chemical substances, chemical reactions and chemical interactions that take place in living organisms. Biochemistry and organic chemistry are closely related, as in medicinal chemistry or neurochemistry. Biochemistry is also associated with the molecular biology and genetics.
Physical chemistry: also known as physical chemistry, study the fundamentals and physical basis of systems and chemical processes. In particular, are of interest to the chemical physical aspects of energy and dynamic of such systems and processes. Among his important area of study include thermodynamics, chemistry, chemical kinetics, electrochemistry, statistical mechanics, and spectroscopy. Usually associated with quantum chemistry and theoretical chemistry.
Industrial chemistry: the Study of the methods of production of chemical reagents in high quantities, in the manner most economically beneficial. Today also attempts to combine their interests upfront, with a low damage to the environment.
Analytical chemistry: the study of the methods of detection (identification) and quantification (determination) of a substance in a sample. It is subdivided into Quantitative and Qualitative.
The difference between organic chemistry and biological chemistry is the chemistry of biological molecules of DNA have a history and, therefore, in its structure to tell us of its history, in the past, that have been formed, while an organic molecule, created today, is only a witness of your present, without a past and without a historical evolution