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Examples and descriptions of heterogeneous mixtures

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Rock On


Credit: Matt Garber
Source: http://www.flickr.com/photos/informant/375865746/
License: CC BY-NC 3.0

The success of a rock’n’roll group today depends not only on talent, but also on showmanship. Flashing lights, choreography, a specific “sound” – all contribute to the overall impact of the band. One typical effect used is the fog machine. Carbon dioxide (CO2) is generated to provide an other-worldly atmosphere to the performance. One advantage of CO2 is that it is heavier than air. This gas will sink to the ground and not dissipate rapidly.

Amazing But True

  • Carbon dioxide is a gas that makes up approximately 0.03% of the atmosphere. It is formed by decomposition of organic materials, by combustion of carbon compounds, and is released when we exhale.
  • Carbon dioxide can be solidified directly from the gaseous state and will transition directly from the solid state to the gaseous state (a process called sublimation).
  • Fog machines depend on a different set of chemical properties. A CO2 generator may be referred to as a fog machine, but technically it is a gas generator. A fog machine utilizes a mixture of materials that form a colloid and make a true fog.
  • Credit: Mike Spasoff
    Source: http://www.flickr.com/photos/clownfish/291072541/
    License: CC BY-NC 3.0

    Fog machines are often used in haunted houses to create a spooky atmosphere [Figure2]


  • Watch the video at the link below to see a demonstration of sublimation: 


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Use the links below to learn more.  Then answer the following questions.

  1. What is used in a machine that generates CO2 gas?
  2. What are two hazards associated with the use of dry ice for fog?
  3. What are the components of “fog” from a true fog machine?
  4. What are some properties of this “fog”?
  5. Why would this “fog” be considered to be a colloid?

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Image Attributions

  1. [1]^ Credit: Matt Garber; Source: http://www.flickr.com/photos/informant/375865746/; License: CC BY-NC 3.0
  2. [2]^ Credit: Mike Spasoff; Source: http://www.flickr.com/photos/clownfish/291072541/; License: CC BY-NC 3.0

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