The disappearing rainbow1 is a wonderful chemistry demonstration previously featured here on ChemEdX.2-4 In this experiment, a colorless solution of NaOH is poured into a row of flasks, each containing a different acid–base indicator. The solutions suddenly flash into the colors of the rainbow—red, orange, yellow, green, blue, and violet. Then, with a pour of HCl, the rainbow vanishes just as quickly.
A few years ago, I showed how the Assassin’s teapot could be used for this demonstration.4 The teapot, with its two compartments, allows one to pour NaOH or HCl from the same vessel. This twist heightens the magical effect—but it’s tricky to pull off. Controlling which liquid comes out requires practice, and spills are common, so I eventually retired using it in the rainbow demo.
That’s why I was excited to try the new Assassin’s water bottle, made by the creators of the Curiosity Box.5 Like the teapot, it has two separate compartments for liquids, but the pouring control is much easier.
It’s a simple upgrade that adds a touch of theatrical magic. I’ll definitely be using this in classroom demonstrations, and I’d love to hear how it works for you.
Happy experimenting!
References
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Flinn Scientific. The Disappearing Rainbow
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https://www.curiositybox.com/pages/assassins-bottle Use the code tom25 for 25% off! (Notice that the author will receive some compensation if this code is used).
Safety
Safety: Video Demonstration
Safety: Video Demonstration
Demonstration videos presented here are not meant as tools to teach chemical demonstration techniques. They are meant as a tool for classroom use. The demonstrations may present safety hazards or show phenomena that are difficult for an entire class to observe in a live demonstration.
Those performing the demonstrations shown in this video have been trained and adhere to best safety practices.
Anyone thinking about performing a chemistry demonstration should first read and then adhere to the ACS Safety Guidelines for Chemical Demonstrations (2016) These guidelines are also available at ChemEd X.
General Safety
General Safety
For Laboratory Work: Please refer to the ACS Guidelines for Chemical Laboratory Safety in Secondary Schools (2016).
For Demonstrations: Please refer to the ACS Division of Chemical Education Safety Guidelines for Chemical Demonstrations.
Other Safety resources
RAMP: Recognize hazards; Assess the risks of hazards; Minimize the risks of hazards; Prepare for emergencies
NGSS
Students who demonstrate understanding can construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.
*More information about all DCI for HS-PS1 can be found at https://www.nextgenscience.org/dci-arrangement/hs-ps1-matter-and-its-interactions and further resources at https://www.nextgenscience.org.
Students who demonstrate understanding can construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.
Assessment is limited to chemical reactions involving main group elements and combustion reactions.
Examples of chemical reactions could include the reaction of sodium and chlorine, of carbon and oxygen, or of carbon and hydrogen.