In Chemical Mystery #18: Peek A Boo Blue,1 Blue Powerade is observed to change to green, and then to a yellow color. When the yellow-colored solution is disturbed by pouring it, it shifts back to green or blue-green. Over time, this green-blue color fades back to yellow. The cycle of blue-colored Powerade fading to yellow, and then restoring a green or blue color by pouring can be repeated several times.
The experiment presented in Chemical Mystery #18 is a fascinating modification of the classic “blue-bottle” reaction.2,3 One of the more interesting aspects of the modified reaction, which was first reported by my friend and colleague, Dean Campbell and his co-workers,4 is that the blue bottle reaction can be mimicked using grocery store items that contain Blue Dye #1 (BD1) like candy or Gatorade.
In the traditional blue bottle reaction, methylene blue in its oxidized, blue-colored form (MB+) reacts with glucose in the presence of base. This generates reduced methylene blue (MBH), which is colorless:2,3,5
MB+ (blue colored) + glucose → MBH (colorless) + colorless products
If a solution containing MBH is disturbed in the presence of air, oxygen gas dissolves into the solution and oxidizes the MBH, regenerating the blue-colored MB+:
MBH (colorless) + O2 → MB+ (blue) + HO2-
As demonstrated in Chemical Mystery #18, the ingredients in Powerade can be used to mimic the traditional blue bottle reaction. Blue Powerade is sweetened with glucose and colored with BD1. Indeed, BD1 can be reduced by glucose in the presence of base to form yellow-colored products:4
BD1ox (blue colored) + glucose → BD1red (colorless) + yellow products
Just like MBH, the colorless form of BD1 can be oxidized by O2:
BD1red (colorless) + O2 → BD1ox (blue)
Thus, simply adding base to Powerade sets up system that mimics the blue bottle reaction (Video 1).
Solution to Peek-a-Boo Blue!
Video: Solution to Peek-a-Boo Blue!, Tommy Technetium YouTube Channel, Aug 18, 2021
As you can see in the video, the use of Powerade tends to cause a color that is more green than blue upon shaking. The green color likely results from a mixture of yellow products and the oxidized, blue-colored BD1. Also, sugar-free Powerade does not work in this experiment because it contains no available sugars that can reduce the BD1.
I have a few questions regarding this reaction that I’m still wondering about. First, what other drinks and grocery store items could be successfully used in this experiment? Can other color changes be generated when doing this experiment with products that contain dyes other than BD1? Some of these questions have been investigated by Campbell,4 but there are several more possibilities that can be tried out. Also, it is reported that the reduction of MB+ can only be achieved with reducing sugars (like glucose).2-4 Based on this, it is likely that this experiment would not work with a drink containing BD1 but sweetened with sucrose (which is not a reducing sugar). Are there any drinks available that can be used to demonstrate this? Maybe you and your students can explore some of these questions. Be sure to let me know in the comments if you try to answer these questions and learn something new.
Happy experimenting!
References and notes:
1. Kuntzleman, T. https://www.chemedx.org/blog/chemical-mystery-18-peek-boo-blue (accessed August 2021).
2. Shakhashiri, B. Z. Chemical Demonstrations; University of Wisconsin Press: Madison, WI 1985; vol. 2, pp. 142-146.
3. Anderson, L.; Wittkopp, S. M.; Painter, C. J.; Liegel, J. J.; Schreiner, R.; Bell, J. A.; Shakhashiri, B. Z. J. Chem. Educ. 2012, 89, 1425-1431.
4. Staiger, F. A.; Peterson, J. P.; Campbell, D. J. J. Chem. Educ. 2015, 92, 1684-1686.
5. Reference 3 contains a very detailed description of the chemistry involved in this experiment.
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
Asking questions and defining problems in grades 9–12 builds from grades K–8 experiences and progresses to formulating, refining, and evaluating empirically testable questions and design problems using models and simulations.
Asking questions and defining problems in grades 9–12 builds from grades K–8 experiences and progresses to formulating, refining, and evaluating empirically testable questions and design problems using models and simulations.
questions that challenge the premise(s) of an argument, the interpretation of a data set, or the suitability of a design.
Scientific questions arise in a variety of ways. They can be driven by curiosity about the world (e.g., Why is the sky blue?). They can be inspired by a model’s or theory’s predictions or by attempts to extend or refine a model or theory (e.g., How does the particle model of matter explain the incompressibility of liquids?). Or they can result from the need to provide better solutions to a problem. For example, the question of why it is impossible to siphon water above a height of 32 feet led Evangelista Torricelli (17th-century inventor of the barometer) to his discoveries about the atmosphere and the identification of a vacuum.
Questions are also important in engineering. Engineers must be able to ask probing questions in order to define an engineering problem. For example, they may ask: What is the need or desire that underlies the problem? What are the criteria (specifications) for a successful solution? What are the constraints? Other questions arise when generating possible solutions: Will this solution meet the design criteria? Can two or more ideas be combined to produce a better solution?
Constructing explanations and designing solutions in 9–12 builds on K–8 experiences and progresses to explanations and designs that are supported by multiple and independent student-generated sources of evidence consistent with scientific ideas, principles, and theories.
Constructing explanations and designing solutions in 9–12 builds on K–8 experiences and progresses to explanations and designs that are supported by multiple and independent student-generated sources of evidence consistent with scientific ideas, principles, and theories. Construct and revise an explanation based on valid and reliable evidence obtained from a variety of sources (including students’ own investigations, models, theories, simulations, peer review) and the assumption that theories and laws that describe the natural world operate today as they did in the past and will continue to do so in the future.
Constructing explanations and designing solutions in 9–12 builds on K–8 experiences and progresses to explanations and designs that are supported by multiple and independent student-generated sources of evidence consistent with scientific ideas, principles, and theories.
Constructing explanations and designing solutions in 9–12 builds on K–8 experiences and progresses to explanations and designs that are supported by multiple and independent student-generated sources of evidence consistent with scientific ideas, principles, and theories. Construct and revise an explanation based on valid and reliable evidence obtained from a variety of sources (including students’ own investigations, models, theories, simulations, peer review) and the assumption that theories and laws that describe the natural world operate today as they did in the past and will continue to do so in the future.
Planning and carrying out investigations in 9-12 builds on K-8 experiences and progresses to include investigations that provide evidence for and test conceptual, mathematical, physical, and empirical models.
Planning and carrying out investigations in 9-12 builds on K-8 experiences and progresses to include investigations that provide evidence for and test conceptual, mathematical, physical, and empirical models. Plan and conduct an investigation individually and collaboratively to produce data to serve as the basis for evidence, and in the design: decide on types, how much, and accuracy of data needed to produce reliable measurements and consider limitations on the precision of the data (e.g., number of trials, cost, risk, time), and refine the design accordingly.