According to Linus Pauling, substances are "homogeneous species of matter with reasonably definite chemical composition." Substances only containing the same item are called pure substances. The two types are elements and compounds.
Pure Substances
A pure substance is a form of matter having a constant composition that cannot be sepearted physically [1]. A pure substance, which can be an element or a compound [2], contains only one substance that is present in the material [3]. That means that all the particles are the same, like the element carbon consisting of all carbon particles and water having all water particles. [4]An elements is a substance that cannot be decomposed into simpler substances by chemical or physical means [2] and when chemically combined, elements form compounds[1]. An example of an element is hydrogen or gold and an example of a compound is H2O, which we all know as water. Lavoisier, a French chemist, was the first to classify pure substances as elements or compounds based on quantitative studies [5]. He showed that when we heat mercuric oxide it changes into mercury and oxygen [5]. Mercuric oxide is a compound because it decomposes into simpler substances, whereas mercury and oxygen cannot be further decomposed into anything simpler as they are elements [5].
Test Your Knowledge:
Which ones are pure substances?
1. Hydrogen
2. Water
3. Ocean
4. Lake
5. Salt water
Answers: 1. yes 2. yes 3. no 4. no 5. no
References
- ↑ 1.0 1.1 "Chapter 1 Matter and Its Origins." Chemistry. 2003. W.W. Norton and Company. 5 Feb 2009 <http://www.wwnorton.com/college/chemistry/gilbert/overview/ch1.htm>.
- ↑ 2.0 2.1 Zumdahl, Steven, Susan Zumdahl, and Donald De Coste. World of Chemistry. USA: Houghton Mifflin Company, 2002.
- ↑ Brown, W.P. "Doc Brown's Chemistry Clinic." 2008. 5 Feb 2009 <http://www.docbrown.info/page01/ElCpdMix/EleCmdMix.htm#COMPOUND>.
- ↑ http://209.85.173.132/search?q=cache:DmyUCIFx8NwJ:www.cybered.net/library/Teaching_Resources/MSS/introWS/5003104WS.pdf+pure+substances+and+mixtures&hl=en&ct=clnk&cd=10&gl=us
- ↑ 5.0 5.1 5.2 http://www.tutorvista.com/content/science/science-i/matter-around-pure/pure-substances.php
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