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Chemical substance

A chemical substance is a form of matter having constant chemical composition and characteristic properties.[1][2] Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., without breaking chemical bonds.[3] Chemical substances can be simple substances (substances consisting of a single chemical element),[4] chemical compounds, or alloys.

Steam and liquid water are two different forms of the same pure chemical substance, that is, water.

Chemical substances are often called 'pure' to set them apart from mixtures. A common example of a chemical substance is pure water; it has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory. Other chemical substances commonly encountered in pure form are diamond (carbon), gold, table salt (sodium chloride) and refined sugar (sucrose). However, in practice, no substance is entirely pure, and chemical purity is specified according to the intended use of the chemical.

Chemical substances exist as solids, liquids, gases, or plasma, and may change between these phases of matter with changes in temperature or pressure and time. Chemical substances may be combined or converted to others by means of chemical reactions.

Definition

 
Colors of a single chemical (Nile red) in different solvents, under visible and UV light, showing how the chemical interacts dynamically with its solvent environment.

A chemical substance may well be defined as "any material with a definite chemical composition" in an introductory general chemistry textbook.[5][page needed] According to this definition a chemical substance can either be a pure chemical element or a pure chemical compound. But, there are exceptions to this definition; a pure substance can also be defined as a form of matter that has both definite composition and distinct properties.[6] The chemical substance index published by CAS also includes several alloys of uncertain composition.[7] Non-stoichiometric compounds are a special case (in inorganic chemistry) that violates the law of constant composition, and for them, it is sometimes difficult to draw the line between a mixture and a compound, as in the case of palladium hydride. Broader definitions of chemicals or chemical substances can be found, for example: "the term 'chemical substance' means any organic or inorganic substance of a particular molecular identity, including – (i) any combination of such substances occurring in whole or in part as a result of a chemical reaction or occurring in nature".[8]

In geology, substances of uniform composition are called minerals, while physical mixtures (aggregates) of several minerals (different substances) are defined as rocks. Many minerals, however, mutually dissolve into solid solutions, such that a single rock is a uniform substance despite being a mixture in stoichiometric terms. Feldspars are a common example: anorthoclase is an alkali aluminum silicate, where the alkali metal is interchangeably either sodium or potassium.

In law, "chemical substances" may include both pure substances and mixtures with a defined composition or manufacturing process. For example, the EU regulation REACH defines "monoconstituent substances", "multiconstituent substances" and "substances of unknown or variable composition". The latter two consist of multiple chemical substances; however, their identity can be established either by direct chemical analysis or reference to a single manufacturing process. For example, charcoal is an extremely complex, partially polymeric mixture that can be defined by its manufacturing process. Therefore, although the exact chemical identity is unknown, identification can be made with a sufficient accuracy. The CAS index also includes mixtures.

Polymers almost always appear as mixtures of molecules of multiple molar masses, each of which could be considered a separate chemical substance. However, the polymer may be defined by a known precursor or reaction(s) and the molar mass distribution. For example, polyethylene is a mixture of very long chains of -CH2- repeating units, and is generally sold in several molar mass distributions, LDPE, MDPE, HDPE and UHMWPE.

History

The concept of a "chemical substance" became firmly established in the late eighteenth century after work by the chemist Joseph Proust on the composition of some pure chemical compounds such as basic copper carbonate.[9] He deduced that, "All samples of a compound have the same composition; that is, all samples have the same proportions, by mass, of the elements present in the compound." This is now known as the law of constant composition.[10] Later with the advancement of methods for chemical synthesis particularly in the realm of organic chemistry; the discovery of many more chemical elements and new techniques in the realm of analytical chemistry used for isolation and purification of elements and compounds from chemicals that led to the establishment of modern chemistry, the concept was defined as is found in most chemistry textbooks. However, there are some controversies regarding this definition mainly because the large number of chemical substances reported in chemistry literature need to be indexed.

Isomerism caused much consternation to early researchers, since isomers have exactly the same composition, but differ in configuration (arrangement) of the atoms. For example, there was much speculation about the chemical identity of benzene, until the correct structure was described by Friedrich August Kekulé. Likewise, the idea of stereoisomerism – that atoms have rigid three-dimensional structure and can thus form isomers that differ only in their three-dimensional arrangement – was another crucial step in understanding the concept of distinct chemical substances. For example, tartaric acid has three distinct isomers, a pair of diastereomers with one diastereomer forming two enantiomers.

Chemical elements

 
Native sulfur crystals. Sulfur occurs naturally as elemental sulfur, in sulfide and sulfate minerals and in hydrogen sulfide.

An element is a chemical substance made up of a particular kind of atom and hence cannot be broken down or transformed by a chemical reaction into a different element, though it can be transmuted into another element through a nuclear reaction. This is because all of the atoms in a sample of an element have the same number of protons, though they may be different isotopes, with differing numbers of neutrons.

As of 2019, there are 118 known elements, about 80 of which are stable – that is, they do not change by radioactive decay into other elements. Some elements can occur as more than a single chemical substance (allotropes). For instance, oxygen exists as both diatomic oxygen (O2) and ozone (O3). The majority of elements are classified as metals. These are elements with a characteristic lustre such as iron, copper, and gold. Metals typically conduct electricity and heat well, and they are malleable and ductile.[11] Around 14 to 21 elements,[12] such as carbon, nitrogen, and oxygen, are classified as non-metals. Non-metals lack the metallic properties described above, they also have a high electronegativity and a tendency to form negative ions. Certain elements such as silicon sometimes resemble metals and sometimes resemble non-metals, and are known as metalloids.

Chemical compounds

 
Potassium ferricyanide is a compound of potassium, iron, carbon and nitrogen; although it contains cyanide anions, it does not release them and is nontoxic.

A chemical compound is a chemical substance that is composed of a particular set of atoms or ions. Two or more elements combined into one substance through a chemical reaction form a chemical compound. All compounds are substances, but not all substances are compounds.

A chemical compound can be either atoms bonded together in molecules or crystals in which atoms, molecules or ions form a crystalline lattice. Compounds based primarily on carbon and hydrogen atoms are called organic compounds, and all others are called inorganic compounds. Compounds containing bonds between carbon and a metal are called organometallic compounds.

Compounds in which components share electrons are known as covalent compounds. Compounds consisting of oppositely charged ions are known as ionic compounds, or salts.

Coordination complexes are compounds where a dative bond keeps the substance together without a covalent or ionic bond. Coordination complexes are distinct substances with distinct properties different from a simple mixture. Typically these have a metal, such as a copper ion, in the center and a nonmetals atom, such as the nitrogen in an ammonia molecule or oxygen in water in a water molecule, forms a dative bond to the metal center, e.g. tetraamminecopper(II) sulfate [Cu(NH3)4]SO4·H2O. The metal is known as a "metal center" and the substance that coordinates to the center is called a "ligand". However, the center does not need to be a metal, as exemplified by boron trifluoride etherate BF3OEt2, where the highly Lewis acidic, but nonmetallic boron center takes the role of the "metal". If the ligand bonds to the metal center with multiple atoms, the complex is called a chelate.

In organic chemistry, there can be more than one chemical compound with the same composition and molecular weight. Generally, these are called isomers. Isomers usually have substantially different chemical properties, and often may be isolated without spontaneously interconverting. A common example is glucose vs. fructose. The former is an aldehyde, the latter is a ketone. Their interconversion requires either enzymatic or acid-base catalysis.

However, tautomers are an exception: the isomerization occurs spontaneously in ordinary conditions, such that a pure substance cannot be isolated into its tautomers, even if these can be identified spectroscopically or even isolated in special conditions. A common example is glucose, which has open-chain and ring forms. One cannot manufacture pure open-chain glucose because glucose spontaneously cyclizes to the hemiacetal form.

Substances versus mixtures

 
Cranberry glass, while appearing homogeneous, is a mixture consisting of glass and colloidal gold particles of about 40 nm in diameter, giving it a red color.

All matter consists of various elements and chemical compounds, but these are often intimately mixed together. Mixtures contain more than one chemical substance, and they do not have a fixed composition. In principle, they can be separated into the component substances by purely mechanical processes. Butter, soil and wood are common examples of mixtures.

Grey iron metal and yellow sulfur are both chemical elements, and they can be mixed together in any ratio to form a yellow-grey mixture. No chemical process occurs, and the material can be identified as a mixture by the fact that the sulfur and the iron can be separated by a mechanical process, such as using a magnet to attract the iron away from the sulfur.

In contrast, if iron and sulfur are heated together in a certain ratio (1 atom of iron for each atom of sulfur, or by weight, 56 grams (1 mol) of iron to 32 grams (1 mol) of sulfur), a chemical reaction takes place and a new substance is formed, the compound iron(II) sulfide, with chemical formula FeS. The resulting compound has all the properties of a chemical substance and is not a mixture. Iron(II) sulfide has its own distinct properties such as melting point and solubility, and the two elements cannot be separated using normal mechanical processes; a magnet will be unable to recover the iron, since there is no metallic iron present in the compound.

Chemicals versus chemical substances

 
Chemicals in graduated cylinders and beaker.

While the term chemical substance is a precise technical term that is synonymous with chemical for chemists, the word chemical is used in general usage to refer to both (pure) chemical substances and mixtures (often called compounds),[13] and especially when produced or purified in a laboratory or an industrial process.[14][15][16] In other words, the chemical substances of which fruits and vegetables, for example, are naturally composed even when growing wild are not called "chemicals" in general usage. In countries that require a list of ingredients in products, the "chemicals" listed are industrially produced "chemical substances". The word "chemical" is also often used to refer to addictive, narcotic, or mind-altering drugs.[14][15]

Within the chemical industry, manufactured "chemicals" are chemical substances, which can be classified by production volume into bulk chemicals, fine chemicals and chemicals found in research only:

  • Bulk chemicals are produced in very large quantities, usually with highly optimized continuous processes and to a relatively low price.
  • Fine chemicals are produced at a high cost in small quantities for special low-volume applications such as biocides, pharmaceuticals and speciality chemicals for technical applications.
  • Research chemicals are produced individually for research, such as when searching for synthetic routes or screening substances for pharmaceutical activity. In effect, their price per gram is very high, although they are not sold.

The cause of the difference in production volume is the complexity of the molecular structure of the chemical. Bulk chemicals are usually much less complex. While fine chemicals may be more complex, many of them are simple enough to be sold as "building blocks" in the synthesis of more complex molecules targeted for single use, as named above. The production of a chemical includes not only its synthesis but also its purification to eliminate by-products and impurities involved in the synthesis. The last step in production should be the analysis of batch lots of chemicals in order to identify and quantify the percentages of impurities for the buyer of the chemicals. The required purity and analysis depends on the application, but higher tolerance of impurities is usually expected in the production of bulk chemicals. Thus, the user of the chemical in the US might choose between the bulk or "technical grade" with higher amounts of impurities or a much purer "pharmaceutical grade" (labeled "USP", United States Pharmacopeia). "Chemicals" in the commercial and legal sense may also include mixtures of highly variable composition, as they are products made to a technical specification instead of particular chemical substances. For example, gasoline is not a single chemical compound or even a particular mixture: different gasolines can have very different chemical compositions, as "gasoline" is primarily defined through source, properties and octane rating.

Naming and indexing

Every chemical substance has one or more systematic names, usually named according to the IUPAC rules for naming. An alternative system is used by the Chemical Abstracts Service (CAS).

Many compounds are also known by their more common, simpler names, many of which predate the systematic name. For example, the long-known sugar glucose is now systematically named 6-(hydroxymethyl)oxane-2,3,4,5-tetrol. Natural products and pharmaceuticals are also given simpler names, for example the mild pain-killer Naproxen is the more common name for the chemical compound (S)-6-methoxy-α-methyl-2-naphthaleneacetic acid.

Chemists frequently refer to chemical compounds using chemical formulae or molecular structure of the compound. There has been a phenomenal growth in the number of chemical compounds being synthesized (or isolated), and then reported in the scientific literature by professional chemists around the world.[17] An enormous number of chemical compounds are possible through the chemical combination of the known chemical elements. As of Feb 2021, about "177 million organic and inorganic substances" (including 68 million defined-sequence biopolymers) are in the scientific literature and registered in public databases.[18] The names of many of these compounds are often nontrivial and hence not very easy to remember or cite accurately. Also it is difficult to keep the track of them in the literature. Several international organizations like IUPAC and CAS have initiated steps to make such tasks easier. CAS provides the abstracting services of the chemical literature, and provides a numerical identifier, known as CAS registry number to each chemical substance that has been reported in the chemical literature (such as chemistry journals and patents). This information is compiled as a database and is popularly known as the Chemical substances index. Other computer-friendly systems that have been developed for substance information, are: SMILES and the International Chemical Identifier or InChI.

Identification of a typical chemical substance
Common name Systematic name Chemical formula Chemical structure CAS registry number InChI
Alcohol, or
ethyl alcohol
Ethanol C2H5OH
 
[64-17-5] 1/C2H6O/c1-2-3/h3H,2H2,1H3

Isolation, purification, characterization, and identification

Often a pure substance needs to be isolated from a mixture, for example from a natural source (where a sample often contains numerous chemical substances) or after a chemical reaction (which often gives mixtures of chemical substances).

See also

References

  1. ^ Hale, Bob (2013-09-19). Necessary Beings: An Essay on Ontology, Modality, and the Relations Between Them. OUP Oxford. ISBN 9780191648342. from the original on 2018-01-13.
  2. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "Chemical Substance". doi:10.1351/goldbook.C01039
  3. ^ Hunter, Lawrence E. (2012-01-13). The Processes of Life: An Introduction to Molecular Biology. MIT Press. ISBN 9780262299947. from the original on 2018-01-13.
  4. ^ Scerri, Eric (2005). "Simples and Compounds". www.iupac.org. Retrieved 15 May 2018.
  5. ^ Petrucci, Ralph H.; Herring, F. Geoffrey; Madura, Jeffry D.; Bissonnette, Carey (2011). General Chemistry: Principles and Modern Applications. Pearson Canada. ISBN 9780137032129. OCLC 967377094.
  6. ^ . Diracdelta.co.uk. Archived from the original on 2013-05-11. Retrieved 2013-06-06.
  7. ^ Appendix IV: Chemical Substance Index Names 2007-12-03 at the Wayback Machine
  8. ^ "What is the TSCA Chemical Substance Inventory?". US Environmental Protection Agency. from the original on 2009-06-05. Retrieved 2009-10-19.
  9. ^ Hill, J. W.; Petrucci, R. H.; McCreary, T. W.; Perry, S. S. General Chemistry, 4th ed., p37, Pearson Prentice Hall, Upper Saddle River, New Jersey, 2005.
  10. ^ Law of Definite Proportions November 18, 2007, at the Wayback Machine
  11. ^ Hill, J. W.; Petrucci, R. H.; McCreary, T. W.; Perry, S. S. General Chemistry, 4th ed., pp 45–46, Pearson Prentice Hall, Upper Saddle River, New Jersey, 2005.
  12. ^ The boundary between metalloids and non-metals is imprecise, as explained in the previous reference.
  13. ^ compound 2017-11-07 at the Wayback Machine in Oxford Online Dictionaries
  14. ^ a b chemical 2017-11-07 at the Wayback Machine in Oxford Online Dictionaries
  15. ^ a b Random House Unabridged Dictionary 2017-11-07 at the Wayback Machine, 1997
  16. ^ . Nicnas.gov.au. 2005-06-01. Archived from the original on 2013-06-16. Retrieved 2013-06-06.
  17. ^ Joachim Schummer. . Rz.uni-karlsruhe.de. Archived from the original on 2013-09-17. Retrieved 2013-06-06.
  18. ^ "Chemical Abstracts substance count". Cas.org. Retrieved Feb 15, 2021.

External links

  •   Media related to Chemical substances at Wikimedia Commons

chemical, substance, chemical, redirects, here, other, uses, chemical, disambiguation, chemical, substance, form, matter, having, constant, chemical, composition, characteristic, properties, some, references, that, chemical, substance, cannot, separated, into,. Chemical redirects here For other uses see Chemical disambiguation A chemical substance is a form of matter having constant chemical composition and characteristic properties 1 2 Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods i e without breaking chemical bonds 3 Chemical substances can be simple substances substances consisting of a single chemical element 4 chemical compounds or alloys Steam and liquid water are two different forms of the same pure chemical substance that is water Chemical substances are often called pure to set them apart from mixtures A common example of a chemical substance is pure water it has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory Other chemical substances commonly encountered in pure form are diamond carbon gold table salt sodium chloride and refined sugar sucrose However in practice no substance is entirely pure and chemical purity is specified according to the intended use of the chemical Chemical substances exist as solids liquids gases or plasma and may change between these phases of matter with changes in temperature or pressure and time Chemical substances may be combined or converted to others by means of chemical reactions Contents 1 Definition 2 History 3 Chemical elements 4 Chemical compounds 5 Substances versus mixtures 6 Chemicals versus chemical substances 7 Naming and indexing 8 Isolation purification characterization and identification 9 See also 10 References 11 External linksDefinition Edit Colors of a single chemical Nile red in different solvents under visible and UV light showing how the chemical interacts dynamically with its solvent environment A chemical substance may well be defined as any material with a definite chemical composition in an introductory general chemistry textbook 5 page needed According to this definition a chemical substance can either be a pure chemical element or a pure chemical compound But there are exceptions to this definition a pure substance can also be defined as a form of matter that has both definite composition and distinct properties 6 The chemical substance index published by CAS also includes several alloys of uncertain composition 7 Non stoichiometric compounds are a special case in inorganic chemistry that violates the law of constant composition and for them it is sometimes difficult to draw the line between a mixture and a compound as in the case of palladium hydride Broader definitions of chemicals or chemical substances can be found for example the term chemical substance means any organic or inorganic substance of a particular molecular identity including i any combination of such substances occurring in whole or in part as a result of a chemical reaction or occurring in nature 8 In geology substances of uniform composition are called minerals while physical mixtures aggregates of several minerals different substances are defined as rocks Many minerals however mutually dissolve into solid solutions such that a single rock is a uniform substance despite being a mixture in stoichiometric terms Feldspars are a common example anorthoclase is an alkali aluminum silicate where the alkali metal is interchangeably either sodium or potassium In law chemical substances may include both pure substances and mixtures with a defined composition or manufacturing process For example the EU regulation REACH defines monoconstituent substances multiconstituent substances and substances of unknown or variable composition The latter two consist of multiple chemical substances however their identity can be established either by direct chemical analysis or reference to a single manufacturing process For example charcoal is an extremely complex partially polymeric mixture that can be defined by its manufacturing process Therefore although the exact chemical identity is unknown identification can be made with a sufficient accuracy The CAS index also includes mixtures Polymers almost always appear as mixtures of molecules of multiple molar masses each of which could be considered a separate chemical substance However the polymer may be defined by a known precursor or reaction s and the molar mass distribution For example polyethylene is a mixture of very long chains of CH2 repeating units and is generally sold in several molar mass distributions LDPE MDPE HDPE and UHMWPE History EditThe concept of a chemical substance became firmly established in the late eighteenth century after work by the chemist Joseph Proust on the composition of some pure chemical compounds such as basic copper carbonate 9 He deduced that All samples of a compound have the same composition that is all samples have the same proportions by mass of the elements present in the compound This is now known as the law of constant composition 10 Later with the advancement of methods for chemical synthesis particularly in the realm of organic chemistry the discovery of many more chemical elements and new techniques in the realm of analytical chemistry used for isolation and purification of elements and compounds from chemicals that led to the establishment of modern chemistry the concept was defined as is found in most chemistry textbooks However there are some controversies regarding this definition mainly because the large number of chemical substances reported in chemistry literature need to be indexed Isomerism caused much consternation to early researchers since isomers have exactly the same composition but differ in configuration arrangement of the atoms For example there was much speculation about the chemical identity of benzene until the correct structure was described by Friedrich August Kekule Likewise the idea of stereoisomerism that atoms have rigid three dimensional structure and can thus form isomers that differ only in their three dimensional arrangement was another crucial step in understanding the concept of distinct chemical substances For example tartaric acid has three distinct isomers a pair of diastereomers with one diastereomer forming two enantiomers Chemical elements Edit Native sulfur crystals Sulfur occurs naturally as elemental sulfur in sulfide and sulfate minerals and in hydrogen sulfide Main article Chemical element See also List of elements An element is a chemical substance made up of a particular kind of atom and hence cannot be broken down or transformed by a chemical reaction into a different element though it can be transmuted into another element through a nuclear reaction This is because all of the atoms in a sample of an element have the same number of protons though they may be different isotopes with differing numbers of neutrons As of 2019 there are 118 known elements about 80 of which are stable that is they do not change by radioactive decay into other elements Some elements can occur as more than a single chemical substance allotropes For instance oxygen exists as both diatomic oxygen O2 and ozone O3 The majority of elements are classified as metals These are elements with a characteristic lustre such as iron copper and gold Metals typically conduct electricity and heat well and they are malleable and ductile 11 Around 14 to 21 elements 12 such as carbon nitrogen and oxygen are classified as non metals Non metals lack the metallic properties described above they also have a high electronegativity and a tendency to form negative ions Certain elements such as silicon sometimes resemble metals and sometimes resemble non metals and are known as metalloids Chemical compounds Edit Potassium ferricyanide is a compound of potassium iron carbon and nitrogen although it contains cyanide anions it does not release them and is nontoxic Main article Chemical compound See also List of organic compounds and List of inorganic compounds A chemical compound is a chemical substance that is composed of a particular set of atoms or ions Two or more elements combined into one substance through a chemical reaction form a chemical compound All compounds are substances but not all substances are compounds A chemical compound can be either atoms bonded together in molecules or crystals in which atoms molecules or ions form a crystalline lattice Compounds based primarily on carbon and hydrogen atoms are called organic compounds and all others are called inorganic compounds Compounds containing bonds between carbon and a metal are called organometallic compounds Compounds in which components share electrons are known as covalent compounds Compounds consisting of oppositely charged ions are known as ionic compounds or salts Coordination complexes are compounds where a dative bond keeps the substance together without a covalent or ionic bond Coordination complexes are distinct substances with distinct properties different from a simple mixture Typically these have a metal such as a copper ion in the center and a nonmetals atom such as the nitrogen in an ammonia molecule or oxygen in water in a water molecule forms a dative bond to the metal center e g tetraamminecopper II sulfate Cu NH3 4 SO4 H2O The metal is known as a metal center and the substance that coordinates to the center is called a ligand However the center does not need to be a metal as exemplified by boron trifluoride etherate BF3OEt2 where the highly Lewis acidic but nonmetallic boron center takes the role of the metal If the ligand bonds to the metal center with multiple atoms the complex is called a chelate In organic chemistry there can be more than one chemical compound with the same composition and molecular weight Generally these are called isomers Isomers usually have substantially different chemical properties and often may be isolated without spontaneously interconverting A common example is glucose vs fructose The former is an aldehyde the latter is a ketone Their interconversion requires either enzymatic or acid base catalysis However tautomers are an exception the isomerization occurs spontaneously in ordinary conditions such that a pure substance cannot be isolated into its tautomers even if these can be identified spectroscopically or even isolated in special conditions A common example is glucose which has open chain and ring forms One cannot manufacture pure open chain glucose because glucose spontaneously cyclizes to the hemiacetal form Substances versus mixtures EditMain article Mixture Cranberry glass while appearing homogeneous is a mixture consisting of glass and colloidal gold particles of about 40 nm in diameter giving it a red color All matter consists of various elements and chemical compounds but these are often intimately mixed together Mixtures contain more than one chemical substance and they do not have a fixed composition In principle they can be separated into the component substances by purely mechanical processes Butter soil and wood are common examples of mixtures Grey iron metal and yellow sulfur are both chemical elements and they can be mixed together in any ratio to form a yellow grey mixture No chemical process occurs and the material can be identified as a mixture by the fact that the sulfur and the iron can be separated by a mechanical process such as using a magnet to attract the iron away from the sulfur In contrast if iron and sulfur are heated together in a certain ratio 1 atom of iron for each atom of sulfur or by weight 56 grams 1 mol of iron to 32 grams 1 mol of sulfur a chemical reaction takes place and a new substance is formed the compound iron II sulfide with chemical formula FeS The resulting compound has all the properties of a chemical substance and is not a mixture Iron II sulfide has its own distinct properties such as melting point and solubility and the two elements cannot be separated using normal mechanical processes a magnet will be unable to recover the iron since there is no metallic iron present in the compound Chemicals versus chemical substances Edit Chemicals in graduated cylinders and beaker Main article Chemical free While the term chemical substance is a precise technical term that is synonymous with chemical for chemists the word chemical is used in general usage to refer to both pure chemical substances and mixtures often called compounds 13 and especially when produced or purified in a laboratory or an industrial process 14 15 16 In other words the chemical substances of which fruits and vegetables for example are naturally composed even when growing wild are not called chemicals in general usage In countries that require a list of ingredients in products the chemicals listed are industrially produced chemical substances The word chemical is also often used to refer to addictive narcotic or mind altering drugs 14 15 Within the chemical industry manufactured chemicals are chemical substances which can be classified by production volume into bulk chemicals fine chemicals and chemicals found in research only Bulk chemicals are produced in very large quantities usually with highly optimized continuous processes and to a relatively low price Fine chemicals are produced at a high cost in small quantities for special low volume applications such as biocides pharmaceuticals and speciality chemicals for technical applications Research chemicals are produced individually for research such as when searching for synthetic routes or screening substances for pharmaceutical activity In effect their price per gram is very high although they are not sold The cause of the difference in production volume is the complexity of the molecular structure of the chemical Bulk chemicals are usually much less complex While fine chemicals may be more complex many of them are simple enough to be sold as building blocks in the synthesis of more complex molecules targeted for single use as named above The production of a chemical includes not only its synthesis but also its purification to eliminate by products and impurities involved in the synthesis The last step in production should be the analysis of batch lots of chemicals in order to identify and quantify the percentages of impurities for the buyer of the chemicals The required purity and analysis depends on the application but higher tolerance of impurities is usually expected in the production of bulk chemicals Thus the user of the chemical in the US might choose between the bulk or technical grade with higher amounts of impurities or a much purer pharmaceutical grade labeled USP United States Pharmacopeia Chemicals in the commercial and legal sense may also include mixtures of highly variable composition as they are products made to a technical specification instead of particular chemical substances For example gasoline is not a single chemical compound or even a particular mixture different gasolines can have very different chemical compositions as gasoline is primarily defined through source properties and octane rating Naming and indexing EditEvery chemical substance has one or more systematic names usually named according to the IUPAC rules for naming An alternative system is used by the Chemical Abstracts Service CAS Many compounds are also known by their more common simpler names many of which predate the systematic name For example the long known sugar glucose is now systematically named 6 hydroxymethyl oxane 2 3 4 5 tetrol Natural products and pharmaceuticals are also given simpler names for example the mild pain killer Naproxen is the more common name for the chemical compound S 6 methoxy a methyl 2 naphthaleneacetic acid Chemists frequently refer to chemical compounds using chemical formulae or molecular structure of the compound There has been a phenomenal growth in the number of chemical compounds being synthesized or isolated and then reported in the scientific literature by professional chemists around the world 17 An enormous number of chemical compounds are possible through the chemical combination of the known chemical elements As of Feb 2021 about 177 million organic and inorganic substances including 68 million defined sequence biopolymers are in the scientific literature and registered in public databases 18 The names of many of these compounds are often nontrivial and hence not very easy to remember or cite accurately Also it is difficult to keep the track of them in the literature Several international organizations like IUPAC and CAS have initiated steps to make such tasks easier CAS provides the abstracting services of the chemical literature and provides a numerical identifier known as CAS registry number to each chemical substance that has been reported in the chemical literature such as chemistry journals and patents This information is compiled as a database and is popularly known as the Chemical substances index Other computer friendly systems that have been developed for substance information are SMILES and the International Chemical Identifier or InChI Identification of a typical chemical substance Common name Systematic name Chemical formula Chemical structure CAS registry number InChIAlcohol orethyl alcohol Ethanol C2H5OH 64 17 5 1 C2H6O c1 2 3 h3H 2H2 1H3Isolation purification characterization and identification EditOften a pure substance needs to be isolated from a mixture for example from a natural source where a sample often contains numerous chemical substances or after a chemical reaction which often gives mixtures of chemical substances See also Edit Chemistry portalHazard symbol Homogeneous and heterogeneous mixtures Prices of chemical elements Dedicated bio based chemical Fire diamond Research chemicalReferences Edit Hale Bob 2013 09 19 Necessary Beings An Essay on Ontology Modality and the Relations Between Them OUP Oxford ISBN 9780191648342 Archived from the original on 2018 01 13 IUPAC Compendium of Chemical Terminology 2nd ed the Gold Book 1997 Online corrected version 2006 Chemical Substance doi 10 1351 goldbook C01039 Hunter Lawrence E 2012 01 13 The Processes of Life An Introduction to Molecular Biology MIT Press ISBN 9780262299947 Archived from the original on 2018 01 13 Scerri Eric 2005 Simples and Compounds www iupac org Retrieved 15 May 2018 Petrucci Ralph H Herring F Geoffrey Madura Jeffry D Bissonnette Carey 2011 General Chemistry Principles and Modern Applications Pearson Canada ISBN 9780137032129 OCLC 967377094 Pure Substance DiracDelta Science amp Engineering Encyclopedia Diracdelta co uk Archived from the original on 2013 05 11 Retrieved 2013 06 06 Appendix IV Chemical Substance Index Names Archived 2007 12 03 at the Wayback Machine What is the TSCA Chemical Substance Inventory US Environmental Protection Agency Archived from the original on 2009 06 05 Retrieved 2009 10 19 Hill J W Petrucci R H McCreary T W Perry S S General Chemistry 4th ed p37 Pearson Prentice Hall Upper Saddle River New Jersey 2005 Law of Definite Proportions Archived November 18 2007 at the Wayback Machine Hill J W Petrucci R H McCreary T W Perry S S General Chemistry 4th ed pp 45 46 Pearson Prentice Hall Upper Saddle River New Jersey 2005 The boundary between metalloids and non metals is imprecise as explained in the previous reference compound Archived 2017 11 07 at the Wayback Machine in Oxford Online Dictionaries a b chemical Archived 2017 11 07 at the Wayback Machine in Oxford Online Dictionaries a b Random House Unabridged Dictionary Archived 2017 11 07 at the Wayback Machine 1997 What is a chemical Nicnas gov au 2005 06 01 Archived from the original on 2013 06 16 Retrieved 2013 06 06 Joachim Schummer Coping with the Growth of Chemical Knowledge Challenges for Chemistry Documentation Education and Working Chemists Rz uni karlsruhe de Archived from the original on 2013 09 17 Retrieved 2013 06 06 Chemical Abstracts substance count Cas org Retrieved Feb 15 2021 External links Edit Media related to Chemical substances at Wikimedia Commons Retrieved from https en wikipedia org w index php title Chemical substance amp oldid 1151993572, wikipedia, wiki, book, books, library,

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