Formation of a Precipitate

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Learners create hard water by mixing Epsom salt and water. Then they compare what happens when soap solution is mixed with hard water and regular water. The precipitate that forms from soap and hard water resembles soap but isn't. Learners then design an experiment to compare this precipitate to soap to distinguish them from each other. [Activity is publicly available through a web crawler capture on Activity write-up only, images are unavailable.]

Quick Guide

Preparation Time:
5 to 10 minutes

Learning Time:
30 to 45 minutes

Estimated Materials Cost:
$1 - $5 per group of students

Age Range:
Ages 6 - 14

Resource Types:
Activity, Experiment/Lab Activity


Materials List (per group of students)

  • Water
  • Epsom salt
  • Piece of Ivory® soap
  • Piece of paper
  • Coffee filter
  • 1 Dropper
  • 2 Popsicle sticks
  • 2 Straws
  • 6 Clear plastic cups
  • 1 Small cup
  • 1 Tablespoon
  • 1 Teaspoon
  • Student Activity Sheet


  • Physical Sciences
    • Chemistry
      • Chemical Reactions
      • Solutions
  • The Nature of Science
    • The Scientific Process
      • About Inquiry
      • Asking Questions
      • Conducting Investigations


To use this activity, learners need to:

  • see
  • 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


  • Kessler, James H. ; Galvan, Patricia M.


  • All rights reserved, American Chemical Society, 2007