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Two or more elements combined in a fixed proportion.

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Credit: Ami du Peuple
Source: http://en.wikipedia.org/wiki/File:Bataille_de_Fleurus_1794.JPG
License: CC BY-NC 3.0

One of the definitions for the word “revolution” from the Oxford English Dictionary is “a dramatic or wide-reaching change in conditions.”  During the 1700s, politics, governments, and science underwent some dramatic changes!

Amazing But True!

  • Antoine Lavoisier, a scientist from the 18th century, is acknowledged to be the father of modern chemistry.  In 1789, Lavoisier published a major work detailing his experiments with oxygen.  He also suggested that when substances burn, a transformation is occurring with the oxygen in the air to form new compounds.  
  • Credit: Wikimedia
    Source: http://en.wikipedia.org/wiki/File:Lavoisier_humanexp.jpg
    License: CC BY-NC 3.0

    Antoine Lavoisier performing experiments on respiration in the 1770s [Figure2]

  • This directly contradicted phlogiston theory, which was the then prevalent explanation for how materials burned.  This of course led to heated debate among scientists of the day.
  • While Lavoisier’s contributions to the foundational development of chemistry were great, they were cut short due to his unfortunate involvement in the French Revolution. 
  • Check out this video to learn more about Antoine-Laurent Lavoisier: http://www.chemheritage.org/discover/online-resources/chemistry-in-history/themes/early-chemistry-and-gases/lavoisier.aspx

Show What You Know

With the links below, learn more about elements, oxygen, and phlogiston theory. Then answer the following questions.

  1. Provide some examples of elements.
  2. Compounds always have more than one atom. The molecule oxygen has two atoms of oxygen in it.  Why is it considered an element and not a compound?
  3. Water is considered one of the “four classical elements” (the others being air, earth, and fire). Water is composed of two atoms of hydrogen and one atom of oxygen. Do chemists consider water to be an element?  Explain.
  4. It turns out that phlogiston theory makes many predictions that are indeed observed. However, it failed to explain certain observations. How does phlogiston theory fail in the case of burning metals?

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Image Attributions

  1. [1]^ Credit: Ami du Peuple; Source: http://en.wikipedia.org/wiki/File:Bataille_de_Fleurus_1794.JPG; License: CC BY-NC 3.0
  2. [2]^ Credit: Wikimedia; Source: http://en.wikipedia.org/wiki/File:Lavoisier_humanexp.jpg; License: CC BY-NC 3.0

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