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Unformatted text preview: 15-4
The Tyndall Effect
Description: A beam of light is projected through a fish tank onto a screen. The fish
tank contains a sodium thiosulfate solution which reacts with sulfuric acid to gradually
produce particles of sulfur. As particles gradually accumulate they scatter the light and
gradually produce blue, yellow, and then red colors on the screen, simulating a sunset.
Concept: Particles in the atmosphere scatter the light from the sun to produce blue sky
and red sunsets.
• 10 gallon Fish Tank
• distilled water
• 120 grams of sodium thiosulfate
• 60 mL of 3 M H2SO4
• Slide projector with a slide cut to form a circular image on the screen
• large stirring rod
• white screen
• 3 demonstrations carts
• wood blocks to prop fish tank
Set up before class:
Set fish tank on wood blocks on one demo cart. Fill tank to about 4 inches
below the top. Add 120 grams of NaS2O3 and stir to dissolve. Put the slide projector
on another demo cart. Put the white screen on a third demo cart. Arrange carts
according to diagram below. The goal when arranging the carts is to set the screen so
that the "sunset" can be seen from all seats in the audience.
Turn projector on, dim room lights, and pour sulfuric acid into fish tank (DO
NOT STIR). Allow 10-15 minutes for color changes to occur. See Diagram on Next Page 15-4 Audience
fish tank slide projector Blackboard white screen
on cart Notes: Demonstration developed by Prof. Ewing who says it is one of the class
favorites. 15-4 ...
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- Winter '08