Phase Changes

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Learners observe a sealed test tube containing a small amount of solid stearic acid. Under adult supervision, learners place the test tube into a beaker of hot water and observe the white stearic acid as it melts into a yellowish liquid. They then place the test tube into a beaker of ice water and observe as the stearic acid re-solidifies. Learners discover that changes in temperature can cause matter to change phases, but doesn't change the molecular structure. For safety reasons, this activity works best as a demonstration for younger audiences.

Quick Guide

Preparation Time:
5 to 10 minutes

Learning Time:
5 to 10 minutes

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

Age Range:
Ages 11 - 18

Resource Types:
Activity, Demonstration, Experiment/Lab Activity


Materials List (per group of students)

  • Two test tubes with rubber stoppers
  • Electrician’s tape
  • Approximately 2-3 g stearic acid
  • One hot plate
  • One test-tube rack
  • Two 600-ml glass beakers
  • Ice


  • Physical Sciences
    • Heat and Thermodynamics
      • Heat and Temperature
    • Chemistry
    • States of Matter
      • Solids
      • Liquids
      • Gases
      • Changes of Phase
    • Structure and Properties of Matter


To use this activity, learners need to:

  • see
  • see color
  • touch

Learning styles supported:

  • Involves hands-on or lab activities


This resource is part of:

Access Rights:

  • Free access



Funding Source:

  • National Science Foundation