A chemical substance is any material with a definite chemical composition, no matter where it comes from. 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. For example, a sample of water has the same properties and the same ratio of hydrogen and oxygen whether the sample is isolated from a river or made in a laboratory. A pure substance cannot be separated into other substances by any mechanical process,Ebbing, D. D.; Gammon, S. D. General Chemistry, 7th ed., p12, Houghton Mifflin, Boston, Massachusetts, 2002.. Typical chemical substances found in the home are water, salt (sodium chloride) and sugar (sucrose). Generally, substances exist as solid, liquid, or gas, and may change between these phases of matter with changes in temperature or pressure.

The concept of chemical substances was established in the eighteenth century by the chemist Joseph Proust. He did careful studies of the composition of some pure chemical compounds such as basic copper carbonate 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. 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 became known as the law of constant composition, and it is one of the foundations of modern chemistry.

Elements

---

More on [ Chemical substance ]

ACS Weekly Newsletter

Noteworthy Chemistry
Mon, 07 Jul 2008 17:00:00 -0500
Use of paclitaxel, a potent anticancer drug, is limited by its severe side effects. Delivery using polymeric nanoencapsulates allows controlled release but has serious deficiencies which limit its applications. Researchers at the University of Illiniois at Urbana-Champaign report a method which features predefined drug loadings, nearly quantitative loading efficiences, and a significant increase in controlled release of the drug with minimum burst-release effects. Read more in the latest edition of Noteworthy Chemistry.
Electronic Chemicals
Mon, 07 Jul 2008 17:00:00 -0500
New materials from chemical companies are helping the electronics industry advance solar power, semiconductors, and lighting.
Exchange Social News
Mon, 07 Jul 2008 17:00:00 -0500
Controlling The Size Of Nanoclusters: First Step In Making New Catalysts To Control Polllution
New on www.acs.org: ChemTechStandards Resource Package
Mon, 07 Jul 2008 16:00:00 -0500
The ChemTechStandards Resource Package is now available to help facilitate chemical technology partnerships among industry, academia, and the community. The package includes tips on using the ChemTechStandards database and a CD filled with useful information about starting and maintaining partnerships, technician skill standards, presentations, and more. E-mail ChemTechLinks@acs.org to request the package.
Graduate School Recruiting Events
Mon, 07 Jul 2008 16:00:00 -0500
College and universities are invited to register for the Graduate School Recruiting Events August 17 and 18 at the ACS national meeting in Philadelphia. This is a great opportunity to meet talented undergraduate students.

Noteworthy Chemistry, a product of the American Chemical Society

Methanol-to-olefins-a new paradigm for olefins production?
Mon, 21 Jul 2008 09:59:18 -0400
Methanol-to-olefins-a new paradigm for olefins production?

Chemical & Engineering News: Latest News

FDA Launches Fellowship Program
Tue, 22 Jul 2008 16:43:00 -0400
Agency aims to attract the best scientists to help it overcome numerous challenges
Roche Bids For Rest Of Genentech
Mon, 21 Jul 2008 16:10:00 -0400
Swiss drugmaker believes the companies will be more innovative together than alone
Lightweight Atoms Imaged
Mon, 21 Jul 2008 11:00:00 -0400
New method renders conventional instruments capable of 'seeing' hydrogen atoms

Subscribe to Chemicals RSS feed

Price forecasts for chemical commodities