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Chemistry: Demo: The Tyndall Effect


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About this Lesson

  • Type: Video Tutorial
  • Length: 2:16
  • Media: Video/mp4
  • Use: Watch Online & Download
  • Access Period: Unrestricted
  • Download: MP4 (iPod compatible)
  • Size: 24 MB
  • Posted: 07/14/2009

This lesson is part of the following series:

Chemistry: Full Course (303 lessons, $198.00)
Chemistry: Physical Properties of Solutions (14 lessons, $22.77)
Chemistry: Colloids (2 lessons, $2.97)

This lesson was selected from a broader, comprehensive course, Chemistry, taught by Professor Harman, Professor Yee, and Professor Sammakia. This course and others are available from Thinkwell, Inc. The full course can be found at The full course covers atoms, molecules and ions, stoichiometry, reactions in aqueous solutions, gases, thermochemistry, Modern Atomic Theory, electron configurations, periodicity, chemical bonding, molecular geometry, bonding theory, oxidation-reduction reactions, condensed phases, solution properties, kinetics, acids and bases, organic reactions, thermodynamics, nuclear chemistry, metals, nonmetals, biochemistry, organic chemistry, and more.

Dean Harman is a professor of chemistry at the University of Virginia, where he has been honored with several teaching awards. He heads Harman Research Group, which specializes in the novel organic transformations made possible by electron-rich metal centers such as Os(II), RE(I), AND W(0). He holds a Ph.D. from Stanford University.

Gordon Yee is an associate professor of chemistry at Virginia Tech in Blacksburg, VA. He received his Ph.D. from Stanford University and completed postdoctoral work at DuPont. A widely published author, Professor Yee studies molecule-based magnetism.

Tarek Sammakia is a Professor of Chemistry at the University of Colorado at Boulder where he teaches organic chemistry to undergraduate and graduate students. He received his Ph.D. from Yale University and carried out postdoctoral research at Harvard University. He has received several national awards for his work in synthetic and mechanistic organic chemistry.

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This is a cute little demonstration called the sunset demonstration. It's an example of the Tyndall Effect, where it's sodium thiosulphate and hydrochloric acid, which combine to form a sol. Remember a sol is a colloid and it's a solid dispersed in a liquid. In this case, the liquid is water inside this aquarium. What we're going to do is we're going to mix the ingredients inside the aquarium and we'll shine a light through. Remember the Tyndall Effect is the scattering of light off the particles that are in the solution. They are not fully dissolved. They are starting to precipitate and just as the sunset turns progressively redder, as the sun goes down, what we're going to see is something along those lines. I won't give away too much.
So, here are the solutions. We're going to pour them into the aquarium. We're going to give it a quick stir and then I'm going to set up some nice sunset music and let you all enjoy it.
I hope you enjoyed that. As the particles of our sol grew larger and larger, it was only the very longest wavelengths of light that were not scattered and so what happens is that we start with white light coming out of our light source and the appearance is more and more red as the sunset progresses because only the longest wavelengths make it through. And that explains why sunsets look red.
Physical Properties of Solutions
CIA Demonstration: Tyndall Effect Page [1 of 1]

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