Chemistry is the scientific discipline involved with compounds composed
of atoms, i.e. elements, and molecules, i.e. combinations of
atoms: their composition, structure, properties, behavior and the changes they
undergo during a reaction with other compounds. Chemistry
addresses topics such as how atoms and molecules interact via chemical
bonds to form new chemical compounds. There are four types of
chemical bonds: covalent bonds, in which compounds share one or more
electron(s); ionic bonds, in which a compound donates one or more electrons to
another compound to produce ions: cations and anions; hydrogen
bonds; and Van der Waals force bonds. See glossary of chemistry.
In the scope of its subject, chemistry occupies an intermediate
position between physics and biology. It is sometimes called the
central science because it provides a foundation for understanding both basic
and applied scientific disciplines at a fundamental level. Examples
include plant chemistry (botany), the formation of igneous rocks (geology), how
atmospheric ozone is formed and how environmental pollutants are degraded (ecology),
the properties of the soil on the moon (astrophysics), how medications work (pharmacology),
and how to collect DNA evidence at a crime scene (forensics).
The history of chemistry spans a period from very old times to
the present. Since several millennia BC, civilizations were using technologies
that would eventually form the basis of the various branches of chemistry.
Examples include extracting metals from ores, making pottery and
glazes, fermenting beer and wine, extracting chemicals from plants for medicine
and perfume, rendering fat into soap, making glass, and making alloys like bronze.
Chemistry was preceded by its protoscience, alchemy, which is an intuitive
but non-scientific approach to understanding the constituents of matter and
their interactions. It was unsuccessful in explaining the nature of matter and
its transformations, but, by performing experiments and recording the results,
alchemists set the stage for modern chemistry. Chemistry as a body of knowledge
distinct from alchemy began to emerge when a clear differentiation was made
between them by Robert Boyle in his work The Sceptical
Chymist (1661). While both alchemy and chemistry are concerned with
matter and its transformations, the crucial difference was given by the scientific
method that chemists employed in their work. Chemistry is
considered to have become an established science with the work of Antoine
Lavoisier, who developed a law of conservation of mass that demanded
careful measurement and quantitative observations of chemical phenomena. The
history of chemistry is intertwined with the history of thermodynamics,
especially through the work of Willard Gibbs.
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