What is the essence of chemistry



The chemistry [çe'mi:(Bavarian, Baden, Austrian: ke'mi :), Pl. Çe'mi: ən(Bavarian, Austrian: ke'mi: ən)] is the doctrine of the structure, behavior and transformation of substances as well as the laws that apply to them.

Chemistry in its present form as an exact natural science gradually emerged in the 17th and 18th centuries from the application of rational reasoning based on observations and experiments in alchemy. Some of the first great chemists were Robert Boyle, Humphry Davy, Jöns Jacob Berzelius, Joseph Louis Gay-Lussac, Joseph-Louis Proust, Marie and Antoine Lavoisier, and Justus von Liebig.

In chemical reactions, bonds between atoms are separated and newly formed, so there is a change in material. Since the properties of atoms that are relevant for chemistry are almost exclusively based on the structure of their electrons (electron shell), fundamental areas of chemistry can also be used as "Physics of the outer electron shell" to be viewed as.

All interventions that leave the type of substance (substance = substance) unchanged (e.g. melting, solidification) belong to physics. Nuclear physics includes changes to the atomic nucleus.

On this topic see also the article Basics of Chemistry and that in Wikipedia.

Word origin

“Chemistry” originated from the modern Greek χημεία [çiːˈmiːa], literally "[the art of metal] foundry" in the sense of "transformation". Today's spelling chemistry at the beginning of the 19th century dissolved the existing since the 17th century as Chymia from. These Chymia was probably a simplification and reinterpretation of what has been documented as a word since the 13th century alchemy ("The art of gold production"), which itself has an ambiguous etymology, for the connotations compare the etymology of the word Alchemy[1]: The word is probably rooted in Arabic al-kīmiyá, which i.a. "Philosopher's Stone" can mean, possibly from ancient Greek χυμεία, chymeía, "The casting", or from Coptic / ancient Egyptian kemi, "Black [e earth]". Compare also Kemet.

General

Chemistry deals with the properties of elements and compounds, with the possible transformations of one substance into another, makes predictions about the properties of previously unknown compounds, provides methods for the synthesis of new compounds and measurement methods to decipher the chemical composition of unknown samples.

Although all substances are made up of comparatively few "types of building blocks", namely from around 80 to 100 of the 118 known elements, the different combinations and arrangements of the elements lead to several million very different compounds, which in turn have very different forms of matter such as water, sand, and plants. and build up animal tissue or PVC plastic. The type of composition ultimately determines the chemical and physical properties of the substances and thus makes chemistry a very extensive science.

Advances in the various sub-areas of chemistry are often the indispensable prerequisite for new knowledge in other disciplines, especially in the fields of biology and medicine, but also in the field of physics and engineering. In addition, they often make it possible to reduce the production costs for many industrial products. For example, improved catalysts lead to lower energy consumption or a new, cheaper reaction route replaces an old one.

  • For medicine, chemistry is indispensable in the search for new drugs and in the manufacture of drugs.
  • The engineering sciences often look for tailor-made materials depending on the application (light materials for aircraft construction, durable and resilient building materials, high-purity semiconductors ...). Their synthesis is one of the tasks of chemistry.
  • In physics z. B. to carry out experiments often highly pure substances are required, the production of which requires special synthesis methods.

Economic importance of chemistry

The chemical industry is - especially in Germany - a very important branch of the economy: In Germany, the turnover of the chemical industry is over 100 billion euros, the number of employees was over 700,000 after the reunification of Germany and has now fallen below 500,000. On the one hand, it produces basic chemicals such as sulfuric acid or ammonia, often in quantities of millions of tons per year, which it then uses to produce fertilizers and plastics, for example. On the other hand, it produces many complex substances, especially drugs, tailor-made for special purposes. The manufacture of computers, fuels and lubricants for the automotive industry and many other technical products is also impossible without industrially manufactured chemicals.

Chemistry in everyday life

Chemical reactions in everyday life take place, for example, when cooking, baking or roasting, whereby it is often the very complex metabolic transformations that take place here that contribute to the typical aroma of the food. Food is chemically broken down into its components during the body's own breakdown processes and also converted into energy. Combustion is a readily observable chemical reaction.

Hair coloring, combustion engines, cell phone displays, detergents, fertilizers, pharmaceuticals and much more are further examples of applications of chemistry in everyday life.

In everyday life, the term 'chemistry' is often used in a restricted sense as an abbreviation for 'product of the chemical industry', for example in 'chemical cleaning': This cleans textiles with (synthetic) solvents. The cleaning process itself is usually a dissolving of the contamination (for example a grease stain) in the solvent and thus not a chemical process (substance conversion) in the actual sense, but a physical process (dissolving). In contrast to this, the dissolving of lime stains with vinegar or lemon juice, sometimes praised as 'cleaning without chemicals', is very much a chemical process, since solid calcium carbonate (lime) is converted by the acids into soluble calcium salts and hydrogen carbonate or carbon dioxide.

Chemistry as a school subject

Main article: Chemistry class

It is the task of chemistry lessons to provide insight into the composition of materials and processes in nature. Conversions of matter in animate and inanimate nature are also based on chemical reactions and should be recognized as such. Likewise, the imparting of scientific knowledge should be used to build an understanding of modern technology and a positive attitude towards it, since chemistry in particular has made a significant contribution to improving people's living conditions through the introduction of new products. Last but not least, chemistry lessons also serve to educate students to become responsible consumers.

Reputation of chemistry

Chemistry has a relatively poor public image - also due to chemical disasters and environmental scandals. Many experts do not feel this is justified in view of the benefits and the general importance of chemistry, because in Europe, among other things, the strict legislation (Chemicals Act, Hazardous Substances Ordinance) guarantees largely safe handling of chemicals. In order to improve the image of chemistry, the year 2003 was declared the "Year of Chemistry" by various sponsoring organizations.

history

  Main articles: History of chemistry, Chronology of chemical discoveries

Chemistry in antiquity consisted of the accumulated practical knowledge of processes of material conversion and the natural philosophical views of antiquity. Chemistry in the Middle Ages evolved from alchemy, which has been practiced in China, Europe and India for millennia.

The alchemists dealt with the refinement of metals (production of gold from other base metals) and with the search for medicines or a panacea for diseases. For the production of gold in particular, the alchemists were looking for an elixir (philosopher's stone, philosopher's stone) that would convert the base (“sick”) metals into noble (“healthy”) metals. The medical branch of alchemy was also looking for an elixir, the elixir of life, a cure for all diseases that would ultimately also confer immortality. However, no alchemist has ever discovered the philosopher's stone or the elixir of life.

Until the end of the 16th century, the world of ideas of the alchemists was usually not based on scientific research, but on facts of experience and empirical recipes. Alchemists conducted a wide variety of experiments on many substances in order to achieve their goals. They wrote down their discoveries and used the same symbols for their notes as were common in astrology. The mysterious nature of their activity and the often fabricated colored flames, smoke or explosions meant that they were known as magicians and witchers and were sometimes persecuted. For their experiments, the alchemists developed the same equipment that is still used today in chemical process engineering.

 

A well-known alchemist was Albertus Magnus. As a cleric, he dealt with this complex of topics and found a new chemical element, arsenic, in his experiments. Only with Paracelsus did alchemy change from a more empirical to a more experimental science, which became the basis of modern chemistry.

Chemistry in modern times received decisive impulses as a science in the 18th and 19th centuries: It was based on measurement processes and experiments - the use of the scales and the demonstrability of hypotheses and theories about substances and the transformation of substances.

Justus von Liebig's work on the mode of action of fertilizers founded agricultural chemistry and provided important insights into inorganic chemistry. The search for a synthetic substitute for the dye indigo for dyeing textiles was the trigger for the groundbreaking developments in organic chemistry and pharmacy. Up until the beginning of the 20th century, Germany had absolute primacy in both areas. This lead in knowledge made it possible, for example, to extract the explosives necessary to wage the First World War with the help of catalysis from the nitrogen in the air instead of from imported nitrates (see Haber-Bosch process).

The self-sufficiency efforts of the National Socialists gave chemistry as a science further impulses. In order to become independent of the imports of crude oil, processes for the liquefaction of hard coal were developed (Fischer-Tropsch synthesis). Another example was the development of synthetic rubber for the manufacture of vehicle tires.

Today chemistry has become an important part of the culture of life. Chemical products surround us everywhere without our being aware of it. However, accidents in large-scale chemical industry, such as those of Seveso and Bhopal, gave chemistry a very negative image, so that slogans such as “Get away from chemistry!” Could become very popular.

Research developed at the turn of the 20th century to such an extent that in-depth studies of atomic structure no longer belong to the field of chemistry, but to atomic physics or nuclear physics. Nevertheless, these researches provided important insights into the nature of chemical metabolism and chemical bonding. Further important impulses came from discoveries in quantum physics (electron orbital model).

Famous chemists

Subjects

For traditional reasons, chemistry is divided into organic and inorganic chemistry, with physical chemistry being added around 1890.

Since Friedrich Wöhler's urea synthesis in 1828, during which the organic substance urea was produced from the inorganic compound ammonium cyanate, the boundaries between substances from inanimate (the "inorganic" substances) and living nature (the organic substances) have been blurring. Living beings also produce a large number of inorganic substances, while almost all organic substances can be produced in the laboratory.

The traditional, but also arbitrary, distinction between inorganic and organic chemistry was retained. One reason is that organic chemistry is largely determined by the molecule, but inorganic chemistry is often determined by ions, crystals, complex compounds and colloids. Another is that the reaction mechanisms and substance structures in inorganic and organic matter differ in many ways.

Another possibility is to split the chemistry according to the target direction into the investigative, 'decomposing' analytical chemistry and into the constructive, product-oriented preparative or synthetic chemistry. In the teaching practice at universities, analytical chemistry is often represented as a subject, while preparative chemistry is dealt with in the context of organic or inorganic chemistry.

There are of course other subject areas, but the ones outlined here are intended to provide a rough overview.

For the relevant main articles, see Chemistry on Wikipedia.

General Chemistry

Main article: Basics of chemistry

General chemistry is understood to be the basics of chemistry, which are important in almost all chemical sub-areas. It thus represents the conceptual foundation of all chemistry: the structure of the atom, the periodic table of the elements (PSE), the chemical bond, the basics of stoichiometry, acids, bases and salts, redox reactions and the basic laws of chemistry.

In contrast to other scientific disciplines, chemistry uses the term technicus “general chemistry” (there is no “general physics”). In this respect, general chemistry is at the beginning of every closer study of chemistry.

See also general chemistry:

Inorganic chemistry

Main article: Inorganic chemistry

This direction, also known as inorganic chemistry, includes, in simple terms, the chemistry of all elements and compounds that do not exclusively contain carbon chains, because these are objects of organic chemistry. Inorganic chemistry deals, for example, with phosphoric acid, silicon and other carbon-free compounds, but also with carbon dioxide, the acids hydrogen cyanide (hydrogen cyanide) and carbonic acid and their salts. But there is still a whole range of compounds, for example organometallic compounds, that cannot be clearly assigned.

Inorganics are about small molecules or about salts or metals in general, so a sum formula is usually sufficient. In a few cases where isomers do exist, systematic names and structural formulas are understandably required, as in organic chemistry. Often these are even based on those of similarly structured substances in organic chemistry (see, for example, silanes).

Historical definition: Inorganic chemistry deals with the chemical elements and reactions of substances that are not produced by organic life (with the help of the hypothetical life force). See also on inorganic chemistry:

Organic chemistry

  Main article: Organic chemistry

Organic chemistry, also known as organic, is the chemistry of the element carbon and its compounds with other elements. Due to its ability to form long chains and the three different carbon-carbon bond options (single, double and triple bonds), many more and usually more complex compounds are known in organic chemistry than in inorganic chemistry. Due to the enormous variety of chains, rings and other compounds, the chemistry of hydrocarbons alone contains a huge number of different substances, which often only differ in a single double bond or only in their structure. In addition, foreign atoms are often built into the hydrocarbon structure. In order to properly identify this myriad of compounds, no more sum formulas are sufficient, which can easily be demonstrated with an example:

C.2H6O can mean:

Ethanol ("Alcohol"):

Dimethyl ether:

As anyone can determine by simply counting, the empirical formula is correct for both substances, which are, however, very different, as can be seen in the corresponding main articles. There are only 9 atoms in total, but a molecular formula alone is no longer a sufficient identification. Now all you have to do is imagine additional atoms and the chaos is perfect.

For this reason there is the IUPAC nomenclature, which assigns every substance (including every inorganic one) a clear, systematic name, even though trivial names (familiar names; e.g. acetic acid) are often used for organic substances.According to these rules, the first substance is ethane (C.2H6) + ol (ending for alcohols, i.e. -OH), i.e. ethanol, and the second meth (methyl (CH3-)) + oxy (-O-) + methane, also called methoxymethane.

Historical definition: It used to be thought that organic substances, as the word "organic" already says, can only be produced by living things. This was attributed to a so-called “vis vitalis”, ie a “life force” that was hidden in these substances. This theory was unchallenged for a long time until Friedrich Wöhler succeeded in 1828 in converting an inorganic substance into an organic one in the laboratory for the first time. Wöhler's famous urea synthesis from ammonium cyanate by heating to 60 ° C: OCN-     

See also:

Physical chemistry

  Main article: Physical chemistry

Physical chemistry is the boundary between physics and chemistry. While in preparative chemistry (organic, inorganic) the question z. B. is: "How can I create a substance", physical chemistry answers more quantitative questions, e. B. “Under what conditions does a reaction take place?” (Thermodynamics), or “how fast is the reaction” (kinetics). Theoretical chemistry, quantum chemistry or molecular physics, which is gaining in importance, tries to determine the properties of substances, chemical reactions and reaction mechanisms on the basis of physical models, e.g. B. quantum theory or quantum electrodynamics and numerical calculations to fathom.

Physical chemistry was founded around 1890 mainly by Svante Arrhenius, Jacobus Henricus van 't Hoff and Wilhelm Ostwald. The latter was also the first publisher of the jointly founded with van 't Hoff in 1887 Physical Chemistry Journal and held the first German chair for physical chemistry in Leipzig.

The first independent institute for physical chemistry was founded in Göttingen in 1895 by Walther Nernst, who completed his habilitation at Ostwald. Other institutes specifically dedicated to physical chemistry followed in quick succession in Leipzig (1897), Dresden (1900), Karlsruhe (1903), Breslau, Berlin (1905) and elsewhere.

Chemists and physicists who work primarily in the field of physical chemistry are also known as physical chemists.

See also about physical chemistry:

biochemistry

  Main article: biochemistry

Theoretical chemistry

  Main article: Theoretical chemistry

Theoretical chemistry is the application of non-experimental (usually mathematical or computer simulation) methods to explain or predict chemical phenomena. Theoretical chemistry can be roughly divided into two directions: some methods are based on quantum mechanics, others on statistical thermodynamics. Important theoretical chemists are or were Linus Pauling, John A. Pople, Walter Kohn and John C. Slater.

See also:

Analytical chemistry

Main article: Analytical chemistry  

 

technical chemistry

  Main article: Technical chemistry
Technical chemistry deals with the conversion of chemical reactions on a laboratory scale to large-scale industrial production.

Chemical reactions from the laboratory cannot simply be transferred to large-scale industrial production. Technical chemistry therefore deals with the question of how many tons of the same product in a factory are created from a few grams of product in the laboratory.

To put it more abstractly: Technical chemistry looks for the optimal conditions for carrying out technically relevant reactions; this is done empirically or more and more through a mathematical optimization on the basis of a model description of the reaction process and the reactor.

Preparation → reaction → preparation

Almost every production in the chemical industry can be divided into these three steps. First of all, the starting materials must be prepared. They may be heated, crushed ... or compressed. The actual reaction takes place in the second step. In the last step, the reaction mixture is finally prepared. Chemical process engineering deals with preparation and processing. Chemical reaction engineering deals with reactions on an industrial scale. See also:

more specific subject areas

 

See also

Portal: chemistry - Overview of Wikipedia content on chemistry

Sources and further information

Individual evidence

  1. Kluge Etymological Dictionary of the German Language, 24th edition, ISBN 3-11-017473-1

literature

Books

  • Charles E. Mortimer: Chemistry - The basic knowledge of chemistry. Thieme 2003, ISBN 3-13-484308-0
  • Eckhard Ignatowitz, Gerhard Haering: Chemistry for school and work; Europe teaching aids, Haan-Gruiten; ISBN 3-8085-7054-8
  • Joachim Kranz; Manfred Kuballa: Chemistry in everyday life, Berlin, 2003, ISBN 3-589-21692-1
  • Basic knowledge school chemistry (2nd edition) Duden, ISBN 3-89818-026-3
  • Manfred Kuballa; Jens Schorn: Chemistry Pocket Teacher. Cornelsen Verlag, Berlin, 1997, ISBN 3-589-20980-1
  • A compilation of selected contributions from the spectrum of science: Digest: Modern Chemistry. Spectrum of Science Verlagsgesellschaft mbH, Heidelberg, June 1995, ISSN 0945-9537
  • Pedro Cintas: The Road to Chemical Names and Eponyms: Discovery, Priority, and Appreciation. Angewandte Chemie 116 (44), pp. 6012-6018 (2004), ISSN 0044-8249

school books

  • Bäurle et al .: Prisma Chemie 7-10, Edition A; Klett-Verlag, Stuttgart; 1st edition (2006), ISBN 3-12-068560-7 (general edition for chemistry classes in the secondary school Class 7-10, edition B on this: ISBN 3-12-068550-0; There are separate editions for the curriculum for each federal state, examples: Prisma Chemie 7/8, edition of North Rhine-Westphalia (2007), ISBN 3-12-068500-3, Prisma NWA / Chemie 4/5, Baden-Württemberg edition (2005), ISBN 3-12-068535-6 among others)
  • Asselborn, Jäckel et al .: chemistry today - upper secondary education; Schroedel-Verlag, Hanover (1998), ISBN 3-507-10630-2 and subsequent editions (for chemistry lessons on high school, from class 11)
  • Amann, Eisner et al .: elements chemistry II; Klett-Verlag, Stuttgart (1991), ISBN 3-12-759800-9 and subsequent editions (also for chemistry lessons at grammar schools, from grade 11)
  • Ignatowitz: Chemistry for school and work; Europe teaching aids, Haan-Gruiten; ISBN 3-8085-7054-8 (For the introductory chemistry class at the professional school, Chemistry as a general education subject)
  • Brink, Fastert, Ignatowitz: Technical mathematics and data evaluation for laboratory professions; Europe teaching aids, Haan-Gruiten; 1st edition (2002); ISBN 3-8085-7171-3 (For chemistry classes at the professional school, Stoichiometry / technical computing chemistry, for chemical professions)
  • Guardian: Substances, particles, reactions. Verlag Handwerk und Technik, Hamburg (2000), ISBN 3-582-01235-2 (Also for vocational chemistry classes at vocational schools)
  • Dehnert, Jäckel et al .: General Chemistry; Schroedel-Verlag, Hanover (1997), ISBN 3-507-10611-6 (For grammar schools and vocational schools, from grade 11, supplementary volume: Organic chemistry,ISBN 3-507-10612-4)

Generally understandable chemistry journals

  • Chemistry in Our Time ISSN 0009-2851
  • Journal of Chemical Education ISSN 0021-9584

Chemical journals (selection)

Organizations

Category: Chemistry