Chemical substance

Definitions and Classification of Chemical Substances

  • A chemical substance is a unique form of matter with constant chemical composition and characteristic properties.
  • Chemical substances may take the form of a single element or chemical compounds.
  • Chemical substances can exist in different physical states or phases without changing their chemical composition.
  • Substances transition between phases of matter in response to changes in temperature or pressure.
  • Some chemical substances can be combined or converted into new substances by means of chemical reactions.
  • Chemical substances can be organic or inorganic substances of a particular molecular identity.
  • Chemical substances can occur as a result of a chemical reaction or in nature.
  • Inorganic solid substances of uniform composition are known as minerals.
  • Chemical substances in law can include pure substances and mixtures with a defined composition or manufacturing process.
  • Polymers are often mixtures of molecules with different molar masses.
  • The concept of a chemical substance was established in the late eighteenth century.
  • An element is a chemical substance made up of a particular kind of atom.
  • Elements cannot be broken down or transformed into a different element by a chemical reaction.
  • There are 118 known elements, with about 80 of them being stable.
  • Chemical compounds are composed of a specific set of atoms or ions.
  • Mixtures contain more than one chemical substance and do not have a fixed composition.
  • Chemical elements can be mixed together to form a mixture.
  • Chemical substances and mixtures are often referred to as chemicals.

Naming and Indexing of Chemical Substances

  • Chemical substances have systematic names according to IUPAC rules.
  • The Chemical Abstracts Service (CAS) uses an alternative naming system.
  • Many compounds have common, simpler names.
  • Chemical substances can be indexed and identified using systematic or common names.
  • Naming conventions help in the organization and identification of chemical substances.
  • Chemical compounds are often given systematic names.
  • Natural products and pharmaceuticals also have simpler names.
  • Chemical compounds can be referred to using chemical formulae or molecular structures.
  • Common methods of identifying chemical substances include using their common names, systematic names, chemical formulas, chemical structures, CAS registry numbers, and InChI.
  • CAS registry numbers are numerical identifiers assigned to each chemical substance in the literature.
  • The Chemical substances index is a database compiled by CAS that includes information on reported chemical substances.
  • SMILES and InChI are computer-friendly systems developed for substance information.
  • Identification of chemical substances is important for accurate referencing and tracking in the literature.

Isolation, Purification, Characterization, and Identification of Chemical Substances

  • Pure substances often need to be isolated from mixtures, whether from natural sources or after chemical reactions.
  • Isolation methods are used to separate desired substances from mixtures.
  • Purification techniques are employed to remove impurities and obtain a higher level of substance purity.
  • Characterization involves determining the properties and composition of a substance.
  • Identification techniques are used to confirm the identity of a substance, such as spectroscopy or chromatography.

Measurement and Stoichiometry

  • Stoichiometry is the study of the quantitative relationships between reactants and products in chemical reactions.
  • The law of conservation of mass states that the total mass of reactants equals the total mass of products.
  • Stoichiometry allows for the calculation of product amounts based on known reactant quantities.
  • Stoichiometry can be used to determine quantities by weight in a reaction described by a balanced equation.
  • Gas stoichiometry deals with reactions involving gases and uses volume ratios or molar masses for mass calculations.

Related Concepts

  • Chemistry portal is a comprehensive resource for chemistry-related information.
  • Hazard symbols are used to indicate the potential dangers associated with chemical substances.
  • Homogeneous and heterogeneous mixtures are different types of mixtures.
  • Prices of chemical elements can vary based on supply and demand.
  • Dedicated bio-based chemicals are substances derived from renewable resources.

Chemical substance Data Sources

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