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The Disappearing Rainbow Demonstration Kit is popular among students and teachers alike. Two colorless solutions are added to seemingly empty beakers, creating a rainbow of colors. Students are amazed when the rainbow then disappears.

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Your students will love this colorful demonstration which is always a teacher favorite at science conventions. A colorless solution is added to each of six seemingly empty beakers. A second colorless solution is then added and each of the six resulting solutions turns a different color of the rainbow. Add more of the first solution and the rainbow of colors disappears. Challenge your students to explain these amazing observations.

The secret is the small amount of indicator or mixture of indicators placed in each beaker before the demonstration. The first solution is hydrochloric acid which keeps the indicators colorless. The second solution is sodium hydroxide which raises the pH and activates the indicators causing a spectrum of color to appear. Enough materials are included to perform the demonstration seven times.

Concepts: Acidbase indicators.
Time Required: 15 minutes
Chemicals Provided: Sodium hydroxide solution, hydrochloric acid solution, indicator solutions of violet, blue, green, yellow, orange and red.

Correlation to Next Generation Science Standards (NGSS)

Science & Engineering Practices

Asking questions and defining problems
Analyzing and interpreting data
Engaging in argument from evidence

Disciplinary Core Ideas

MS-PS1.A: Structure and Properties of Matter
MS-PS1.B: Chemical Reactions
HS-PS1.A: Structure and Properties of Matter
HS-PS1.B: Chemical Reactions

Crosscutting Concepts

Patterns
Cause and effect
Scale, proportion, and quantity
Stability and change

Performance Expectations

MS-PS1-2. Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred.
HS-PS1-2. 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.