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ChemWiki: The Dynamic Chemistry E-textbook > Development Details > Approaches > Demos > Additional Demos > An Analogy for Elements Versus Mixtures Versus Compounds

An Analogy for Elements Versus Mixtures Versus Compounds

Chemical Concepts Demonstrated

  • Comparitive properties of elements
  • Mixtures
  • Compounds

Demonstration

  • "Crispix" vs. "Raisin Bran" vs. "Wheaties"
  • Brass is a mixture of the elements of copper and zinc.
  • Bronze is a mixture of copper and tin.
  • Water is a compound of the elements hydrogen and oxygen.
  • Cinnabar is a compound that contains mercury and sulfur.

What is the difference between mixtures of elements and compounds formed when elements combine chemically?

Crispix has the properties of a compound.  It is made up of "elements" of corn and rice in a constant 1:1 ratio, and they are not easy to separate from each other.

The composition of Raisin Bran varies from scoop to scoop and is a mixture of raisin and flake "elements" that can be easily separated.

Brass and bronze are made up of varying amounts of metals, depending on how it is made.  The elements are not bonded in constant ratios, much like the raisins and flakes in Raisin Bran.  Therefore, brass and bronze are simply mixtures of elements.  Metal mixtures are called alloys.  It should be noted that alloys still have the properties of metals.

Water and cinnabar, however, have a constant composition.  Regardless of the source, for example, water will always contain eight times as much oxygen by weight as hydrogen.  These elements are usually much more difficult because of chemical bonding.  Water and cinnabar are compounds.  It should be noted that compounds don't necessarily retain the properties of their constituent elements.  Water, for example, has very few of the properties of either hydrogen or oxygen.

The flakes of Wheaties included in the video represent a single element.

Contributors

  • Dr. George Bodner

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Last Modified
10:27, 2 Oct 2013

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