Chemical substance



 Chemistry Portal

 

A chemical substance is a material with a definite chemical composition. It is a concept that became firmly established in the late eighteenth century after work by the chemist 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.

A common example of a chemical substance is pure pressure.

Defining

Chemical substances (also sometimes referred to as a pure substances) are often defined as any material with a definite chemical composition in most introductory general chemistry textbooks.[3] According to this definition a chemical substance can either be a pure chemical element or a pure chemical compound. However, 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.[4] and the chemical substance index published by palladium hydride.

Elements

Main article: Chemical element

An isotopes, with differing numbers of neutrons.

There are about 120 known elements, about 80 of which are stable, that is, they do not change by metalloids.

See also: List of elements by name

Chemical compounds

Main article: Chemical compound

A pure chemical compound is a chemical substance that is composed of a particular set of organometallic compounds.

Compounds in which components share electrons are known as salts.

In organic chemistry, there can be more than one chemical compound with the same composition and molecular weight. Generally, these are called hemiacetal form.

See also: list of inorganic compounds

Substances versus mixtures

Main article: Mixture

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 magnet to attract the iron away from the sulfur.

In contrast, if iron and sulfur are heated together in a certain ratio (56 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

While the term chemical substance is a somewhat technical term used most often by professional chemists, the word chemical[8] is more widely used in the chemical industry.

Naming and Indexing

Every chemical substance has one or more systematic names, usually named according to 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 Naproxen is the more common name for the chemical compound (S)-6-methoxy-α-methyl-2-naphthaleneacetic acid.

International Chemical Identifier or InChI.

Identification of a typical chemical substance
Common name InChI
alcohol, or
ethyl alcohol 		ethanol C2H5OH
[64-17-5] 1/C2H6O/c1-2-3/h3H,2H2,1H3

Isolation, purification, characterisation 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 give mixtures of chemical substances).

References and notes

  1. ^ 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.
  2. ^ http://dbhs.wvusd.k12.ca.us/webdocs/AtomicStructure/LawofDefiniteProportion.html
  3. ^ Hill, J. W.; Petrucci, R. H.; McCreary, T. W.; Perry, S. S. General Chemistry, 4th ed., p5, Pearson Prentice Hall, Upper Saddle River, New Jersey, 2005
  4. ^ http://www.diracdelta.co.uk/science/source/p/u/pure%20substance/source.html
  5. ^ http://www.cas.org/ASSETS/58D34DD3892142D18F5C3B0A004D3A0C/indexguideapp.pdf
  6. ^ Hill, J. W.; Petrucci, R. H.; McCreary, T. W.; Perry, S. S. General Chemistry, 4th ed., pp45-46, Pearson Prentice Hall, Upper Saddle River, New Jersey, 2005.
  7. ^ The boundary between metalloids and non-metals is imprecise, as explained in the previous reference.
  8. ^ What is a chemical
  9. ^ http://www.bfr.bund.de/cd/569
  10. ^ http://www.rz.uni-karlsruhe.de/~ed01/Jslit/eduquim.htm
  11. ^ Chemical Abstracts substance count
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Chemical_substance". A list of authors is available in Wikipedia.