Chemical substance definition of chemical substance by Medical dictionary https: This is one of a series of simple pages introducing key concepts in introductory chemistry.
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. 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. The former is an aldehyde , the latter is a ketone. Their interconversion requires either enzymatic or acid-base catalysis. However, tautomers are an exception: 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.
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.
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.
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 in the English speaking world to refer to both pure chemical substances and mixtures often called compounds ,  and especially when produced or purified in a laboratory or an industrial process. 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. 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:. 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.
For example, gasoline is not a single chemical compound or even a particular mixture: Every chemical substance has one or more systematic names , usually named according to the IUPAC rules for naming. 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. 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. As of May , about sixty million chemical compounds are known.
Also it is difficult to keep the track of them in the literature. 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: 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.
From Wikipedia, the free encyclopedia. For other uses, see Chemical disambiguation. List of organic compounds and List of inorganic compounds. Archived from the original on This definition and interpretation is generally considered sufficient for school-level, incl GCSE Chemistry. There are, however, some other definitions e. A pure substance cannot be separated into simpler components without chemical change. Physical changes can alter the state of matter but not the chemical identity of a pure substance.
Chemical Symbol or Formula. This is one of a series of simple pages introducing key concepts in introductory chemistry. Other pages in this section include elements, mixtures and compounds and individual pages about substances , elements , mixtures and compounds , plus pages about atoms , molecules and isotopes. If you need further information ask your chemistry tutor. See related pages listed top-left or visit the Introduction to Chemistry page.
Further information may be found by entering a search term below:. An important purpose of education is to help learners discover and explore their own talents and interests. To achieve this it is is necessary to genuinely try many subjects. Also on this website: What is Organic Chemistry?
What is Inorganic Chemistry? What is an element? What is a compound? What is a mixture? What is a substance? What is an atom?
A chemical substance is a form of matter having constant chemical composition and characteristic properties ·. It cannot be separated into components by physical separation methods, i.e., without breaking chemical bonds. Chemical substances can be simple substances, chemical compounds, or . explosive - a chemical substance that undergoes a rapid chemical change (with the production of gas) on being heated or struck material, stuff - the tangible substance that goes into the makeup of a physical object; "coal is a hard black material"; "wheat is the stuff they use to make bread. chemical substance Pharmacology Any substance including alcohol, drugs, or medications–eg, those taken pursuant to a valid prescription for legitimate medical purposes, and in accordance with the prescriber's direction, as well as those taken illegally. See Substance abuse.