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1.4: A Description of Matter

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    • Anonymous
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    Pure substances have an invariable composition and are composed of either elements or compounds.

    • Elements: "Substances which cannot be decomposed into simpler substances by chemical means".
    • Compounds: Can be decomposed into two or more elements.



    Elements are the basic substances out of which all matter is composed.

    • Everything in the world is made up from only 109 different elements.
    • 90% of the human body is composed of only three elements: Oxygen, Carbon and Hydrogen

    Elements are known by common names as well as by their abbreviations. These consisting of one or two letters, with the first one capitalized. These abbreviations are derived from English or foreign words (e.g. Latin, German).

    Element Abbreviation
    Carbon C
    Fluorine F
    Hydrogen H
    Iodine I
    Nitrogen N
    Oxygen O
    Phosphorus P
    Sulfur S
    Aluminum Al
    Barium Ba
    Calcium Ca
    Chlorine Cl
    Helium He
    Magnesium Mg
    Platinum Pt
    Silicon Si
    Copper Cu (from cuprum)
    Iron Fe (from ferrum)
    Lead Pb (from plumbum)
    Mercury Hg (from hydrargyrum)
    Potassium K (from kalium)
    Silver Ag (from argentum)
    Sodium Na (from natrium)
    Tin Sn (from stannum)

    Different Definitions of Matter:


    Compounds are substances of two or more elements united chemically in definite proportions by mass. For example, pure water is composed of the elements hydrogen (H) and oxygen (O) at the defined ratio of 11 % hydrogen and 89 % oxygen by mass.

    The observation that the elemental composition of a pure compound is always the same is known as the law of constant composition (or the law of definite proportions). It is credited to the French chemist Joseph Louis Proust (1754-1826).

    Contributors and Attributions

    Mike Blaber (Florida State University)

    This page titled 1.4: A Description of Matter is shared under a CC BY-NC-SA 3.0 license and was authored, remixed, and/or curated by Anonymous.

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