Rainbow Connection

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Chemistry: Acids and Bases, Indicators
Grade Range: Elementary School, Middle School, High School
Format: Stage

Coordinated to The Rainbow Connection by Kermit the Frog, this demonstration is a sight to behold for all ages. Students and teachers alike will enjoy watching the solutions go from colorless to colorful and back again! This demonstration does require a lot of preparation prior to the event, and should be practiced beforehand as well.

Materials

  • Six Indicator Solutions (See Preparation)
  • Sodium Hydroxide
  • Sulfuric Acid
  • Water
  • Ethanol
  • Glycerol
  • Six 1000mL Beakers
  • 4000mL Beaker
  • 2L Pitcher
  • Two 500mL Bottles
  • Seven 50mL Bottle
  • Large Stir Rod
  • Eyedropper
  • Small Cloth
  • Fluorescent Light Box
  • "Rainbow Connection" song w/speaker system

Safety Precautions

Please read the Liquid Chemical section of the Demonstration Safety page before performing this demonstration. All solutions in this demonstration are of low concentrations, and the final solution can be safely poured down a drain.

This demonstration requires: Safety glasses

Demonstration

Preparation
  • Prepare the .015M Sodium Hydroxide (NaOH) solutions: Mix 1.2g of NaOH with 2000mL of DI water. Store in a 2L plastic pitcher, and label and date it.
  • Prepare the .2M NaOH solution: Mix 1.2g of NaOH with 200mL of DI water. Store in a 500mL plastic bottle, and label and date it.
  • Prepare the .05M Sulfuric Acid (H2SO4) solution: Mix 1.025mL of H2SO4 with 250mL of water. Once mixed, add 250mL of ethanol. Store in a 500mL bottle, and label and date it.
  • Prepare the Acid Glycerol: Measure 20mL of glycerol in a small beaker, and measure 10mL of H2SO4 with a small graduated cylinder. slowly mix the H2SO4 into the glycerol, which will turn yellow and heat up as it is added. Once all the acid is in, store the solution in a 50mL bottle, and label and date it.
  • Prepare the indicators: Mix each of the following indicator ratios with 30mL of ethanol. Store the indicator solutions in 50mL bottles, and label and date them.
    • Red: 1.5 g Phenolphthalein with 3.0 g m-Nitrophenol
    • Orange: 0.45g Phenolphthalein with 6.0 g m-Nitrophenol
    • Yellow: 6.0 g m-Nitrophenol
    • Green: 0.6 g Thymolphthalein with 6.0 m-Nitrophenol
    • Blue: 1.5 g Thymolphthalein
    • Violet: 0.9 g Phenolphthalein with 0.4 g Thymolphthalein
Presentation
  1. 1-2 hours prior to the event, use an eyedropper to put 3-5 drops of each indicator into their respective beakers. Have the drops land in the center of the beaker, and allow them to dry.
  2. Set up the demonstration: put the light box on a table and plug it in, keeping the lights off. Set the beakers on the light box in color order, having the sides with the letter labels facing the box. plug in/hook up the stereo system, making sure you have The Rainbow Connection ready to play. Put 5-10mL of the acid glycerol in the bottom of the 4000mL beaker and set it next to the light box. Set the solutions on the table, either alongside the light box or behind it, as well as the eyedropper, stir rod, cloth.
  3. When ready to present this demonstration, Get the audience's attention and announce that you will be showing them a short presentation accompanied by a song. Ask the audience to stay quiet throughout the song, stating that you will be answering questions at the end.
  4. Start The Rainbow Connection, and proceed with the demonstration. Once you finish the demonstration, ask the audience for any questions before proceeding with the explanation.
    • NOTE: This demonstration is coordinated to the song. In order to perform this demonstration, you will need to have learned the timing and rhythm of the song so you don't miss any of the steps. It is required that you practice this demonstration prior to presenting it because of this.
Time Part of Song Action
0:00 - 0:08 Intro None
0:08 - 0:16 Intro Turn on lights in light box
0:16 - 0:40 1st & 2nd Lines of Lyrics Pick up beakers in succession, and mime wiping them clean with the cloth. While doing so, don't break the films in the bottoms of the beakers.
0:40 - 0:52 3rd Line of Lyrics Pour 100mL of the .05M H2SO4 solution into each of the beakers.
0:52 - 1:04 Refrain Pour 100mL of the .015M NaOH solution into each of the beakers. Each one will have a slight flash of color, but they all will stay clear.
1:04 - 1:10 Transition Look at the beakers confused, pondering why they didn't change color.
1:10 - 1:34 4th & 5th Line of Lyrics Pour another 200-300mL of the .015M NaOH solution into each of the beakers. They will all become colored!
1:34 - 1:58 6th Line of Lyrics & Refrain Put a few drops of the acid glycerol into each beaker, stirring as you add them, until they lose their color.
1:58 - 2:10 Bridge Look at the beakers, then at the audience. Give the audience a sad face, then snap your fingers and act excited.
2:10 - 2:22 7th Line of Lyrics Shuffle around with the bottles and solutions, acting like you are trying to find a particular bottle. Excitedly show the bottle with the .2M NaOH solution to the audience, and look between them and the beakers with a big grin.
2:22 - 2:46 8th & 9th Line of Lyrics Pour 30-40mL of the .2M NaOH solution into each beaker while stirring to bring the color back. After finding the color for each beaker, stand back and mime "Ta-da!" to the audience.
2:46 - 2:58 Refrain Sing along with the refrain. Try to get the audience to sing with you!
2:58 - 3:14 Conclusion Pour all the solutions in the beakers into the large beaker. The colors for each of them will vanish as you do so.

Why This Works

The Rainbow Connection is a dramatic demonstration about acids and bases. Acids are solutions that have a free positive ion, such as the hydrogen ion (H+), while Bases are solutions that have a free negative ion, such as the hydroxide ion (OH-). A notable fact about acids and bases are that they neutralize each other; if you add equal concentrations of an acid to a base, then the solution will be neutral. Acids and bases have a wide variety of uses, and are both used extensively in all kinds of products and materials.

Acid/Base Examples Common Uses
Strong Acids Hydrochloric Acid (HCl)

Sulfuric Acid (H2SO4)

Toilet Bowl Cleaner (Dilute HCl)

Car Batteries (H2SO4)

Strong Bases Sodium Hydroxide (NaOH)

Calcium Hydroxide (Ca(OH)2)

Manufacturing of Soap, Paper and Rayon (NaOH)

Bleaching Powder (Ca(OH)2)

Weak Acids Acetic Acid (CH3COOH)

Citric Acid (C6H8O7)

Cooking & Cleaning (Vinegar = dilute CH3COOH)

Vitamins and Fruits (Vitamin C = C6H8O7)

Weak Bases Baking Soda (NaHCO3)

Calcium Carbonate (CaCO3)

Baking and Fire Suppressant (NaHCO3)

Antacids and Chalk (CaCO3)

Normally, you cannot tell from looking at a solution if it is acidic or basic. This is why we are using Acid-Base Indicators in our solutions. Acid-base indicators are compounds that, when exposed to an acidic or basic solutions, undergo a color shift. In this demonstration, all of the indicators we use are sensitive to basic solutions, and will become colored when they are exposed to a base. By using a mix of different types of indicators, as well as by making the solution basic, we can get a rainbow of colors to form!

Additional Information

  • The Rainbow Connection by Kermit the Frog was first sung in 1979, and made it on the list of the 25 most popular songs for that year.
  • This demonstration pairs well with the Shaking Solution and the Bouncing Raisins demonstrations.
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