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

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ACS Matters Weekly Newsletter

FEATURE: New Officer Leadership Training in Ft. Worth, TX
Tue, 17 Nov 2009 13:30:00 -0500
The 2010 Leadership Institute for newly-elected ACS officers is planned for January 22-24, 2010, in Ft. Worth, Texas. The goal of the Leadership Institute is to provide vital education and training to enable ACS volunteers, especially chair-elects, to lead their groups with great success. This jam-packed weekend includes track time where participants will gain an understanding of the essential elements of being an effective ACS volunteer leader, as well as many opportunities to interact and exchange ideas with other local section and division officers, new committee chairs, and ACS governance. In addition, participants will have the opportunity to participate in two ACS Leadership Development System courses that help develop core leadership skills important in ACS volunteer positions as well as the workplace. All new division and local section chairs-elect are invited to join us for this powerful Leadership Institute; more information and online registration can be found at www.acs.org/leaderdevelopment. Attendees are encouraged to register early and to take the online course ACS and You prior to the conference.
US-China Workshops for Early Career Chemical Researchers
Tue, 17 Nov 2009 13:30:00 -0500
During the week of October 26, 2009, a delegation of highly esteemed early-career scientists from the US traveled to Beijing to take part in parallel workshops on New Materials (with sub-themes including: Energy, Nano and Bio/Medicinal Chemistry) and Supramolecular Chemistry. These workshops, funded jointly by a grant from the US National Science Foundation and the Chinese National Natural Science Foundation, aim to foster long-term collaborative relationships between promising early career researchers from the US and China, to tackle jointly some of the most daunting challenges facing the world today. More information about the workshops is available online, including session summaries and meeting proceedings.
Chemical Sciences and Society Symposium (CS3) White Paper
Tue, 17 Nov 2009 13:30:00 -0500
The ACS Office of International Activities, working on behalf of the ACS Committee on International Activities, has released a white paper, "Powering the World with Sunlight," developed during the 2009 Chemical Sciences and Society Symposium (CS3). The CS3 series, hosted by the funding agencies and chemical societies of the US, Germany, China, Japan, and the UK, convenes eminent researchers from each participating country to explore frontier chemistry research and its potential application to global challenges. The focus of the first CS3 meeting was solar energy, with a meeting theme "Sunshine to Power the World," and the meeting was held in Kloster Seeon, with Germany serving as host. Powering the World with Sunlight includes advice to policymakers highlighting the role of chemical research in reaching solutions to energy challenges and offering advice on promising research directions for advancement in solar energy. Plans are underway for a 2010 CS3 meeting, pending support from the five funding agencies, to be held in the UK with a focus on Sustainable Materials.
Share Your NCW 2009 Success Stories
Tue, 17 Nov 2009 13:30:00 -0500
If your local section had a great event or activity for National Chemistry Week (NCW) 2009, why not share your story with other NCW fans and organizers? A key component of the success of NCW over the years has been the exchange of great ideas that really make an impact. Sharing your experience will help lay the groundwork for strong NCW programs in the years ahead; thanks to great online tools, it's never been easier to tell your section's success story. The ACS Office of Community Activities staff uses the ACS Network NCW Group and Facebook (search "Meg A. Mole" or "National Chemistry Week") as a place to hold discussions on event planning, collaborations, and sharing your successes. By completing the online Post NCW 2009 Survey. Your input and feedback help strengthen the NCW program going forward. The first 50 completed survey entrants will be eligible for a drawing to win Elemento, the chemistry-based board game.
Apply Now for Summer Research Opportunities
Tue, 17 Nov 2009 13:30:00 -0500
The ACS-IREU Program is Welcoming Applications for Participation in summer 2010. This NSF-funded international research program provides opportunities for undergraduates majoring in chemistry, biochemistry, materials science or chemical engineering to conduct intensive research for 10 weeks in laboratories in France, Italy, Germany, or the UK To qualify, students must be in their sophomore or junior year, have one semester or summer of prior research experience, and must be US citizens or permanent US residents. Members of underrepresented minority groups are encouraged to apply.




Chemical & Engineering News: Latest News

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