The Liquid Rainbow

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Learners are challenged to discover the relative densities of colored liquids to create a rainbow pattern in a test tube. Five different solutions—3 mixtures of ethyl alcohol, food color and water; red colored water; and pure ethyl alcohol—are used in various combinations. Learners carefully add the solutions to test tubes and observe their relative densities to find the correct order for making a rainbow. Young learners will require adult supervision because of flammable and irritating ingredients.

Quick Guide

Preparation Time:
10 to 30 minutes

Learning Time:
10 to 30 minutes

Estimated Materials Cost:
$5 - $10 per group of students

Age Range:
Ages 4 - 14

Resource Types:
Activity, Experiment/Lab Activity


Materials List (per group of students)

  • 50 6-mm culture tubes or 10-mm test tubes (The large number eliminates the need to constantly wash and replace test tubes.)
  • 25 60-ml plastic dropping bottles
  • 5 plastic cups for discarded mixtures of solutions
  • 5 simple test tube holders
  • Water
  • 95% Ethanol
  • Food coloring (red, blue, yellow, green)
  • Rack for pipettes
  • Paper towels for spills
  • A container of clean water
  • A safe container to dump solutions into and seal (waste container)


  • Physical Sciences
    • Chemistry
      • Solutions
    • Vibration and Waves
      • Light and Optics
    • States of Matter
      • Liquids
    • Structure and Properties of Matter
      • Volume and Density
  • The Nature of Science
    • The Scientific Process
      • Conducting Investigations


To use this activity, learners need to:

  • see
  • see color
  • touch

Learning styles supported:

  • Involves hands-on or lab activities


Components that are part of this resource:

This resource is part of:

Access Rights:

  • Free access



Funding Sources:

  • Camille and Henry Dreyfus Foundation, Inc.
  • American Chemical Society