Chemical Mystery #16: A Red, White, and Blue Chemistry Trick for You!

Red, White, and Blue

Another school year has come and gone, and summertime is upon us! Soon we’ll all be enjoying cookouts, summer conferences (ChemEd 2019, anyone?), swimming at the beach, and fireworks on the Fourth of July.

Speaking of the Fourth, I thought I’d share a color-changing “Chemical Mystery” that displays a summertime/Fourth of July theme. The chemistry involved is relatively simple, but how the trick is carried out allows for a wide variety of interesting possibilities. Watch the demonstration in Video 1 below.  I’ll share the solution with you after a few days. Happy summer, and I hope to see you at ChemEd in Naperville!

Video 1: Tommy Technetium YouTube Channel, Published 6/7/19 (accessed 6/7/19)

Check out the !

Safety

General Safety

For Laboratory Work: Please refer to the ACS .  

For Demonstrations: Please refer to the ACS Division of Chemical Education .

Other Safety resources

: Recognize hazards; Assess the risks of hazards; Minimize the risks of hazards; Prepare for emergencies

 

NGSS

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.

Summary:

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.

Assessment Boundary:
Clarification:

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.

Summary:

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.

Assessment Boundary:
Clarification:

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  and further resources at .

Summary:

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 Boundary:

Assessment is limited to chemical reactions involving main group elements and combustion reactions.

Clarification:

Examples of chemical reactions could include the reaction of sodium and chlorine, of carbon and oxygen, or of carbon and hydrogen.

Join the conversation.

Comments 2

Flint Smith | Wed, 06/12/2019 - 19:01

The explanation my students would come up with first would be the simplest:  food-coloring hidden in the caps.  A tiny droplet, allowed to dry, would leave an easily-hidden, small black deposit that would match the color of the caps.  The dye would dissolve slowly, producing the gradual color change observed.

It doesn't match your keyword list though.  Given the pH/indicator hint, I think one bottle has CO2 gas in it, one air and one ammonia.  Shaking them dissolves the gasses, lowers the pH in the CO2 bottle and raises it in the NH3 bottle.

     NH3 + H2O <==> NH4+ + OH-    and        CO2 +H2O <==> HCO3- + H+ 

Congo Red! Red when basic, blue when acidic and colorless(?) between pH 3.1 and 4.9

Do the red one first.  The ammonia is less dense than air so the open lid is problematic.  Carbon dioxide will stay in the bottle happily.  Unscrew the caps from right to left, fill, then close them from left to right.  It would be nice to have a student randomize the caps but can't risk them smelling the ammonia.

Tom Kuntzleman's picture
Tom Kuntzleman | Thu, 06/13/2019 - 06:20

Hi Flint - great guesses - and great ideas, I might add. I think many combinations of chemical tricks are possible with this bottle/lid set up. I hadn't thought of having gases present in the bottles, but that's a great idea. You can see how I accomplished this particular trick . If you end up trying different combinations of solutions, substances in caps, and gases in bottles to achieve different effects, I'd love to hear what kinds of effects you can achieve.