Changing the Density of a Liquid: Heating and Cooling

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Learners investigate how the temperature of water affects its density. Learners place colored hot and cold water in a cup of room-temperature water to see that cold water sinks while hot water floats. Then they will use this experience to suggest how colored hot and cold water should be stacked to prevent mixing. [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:
10 to 30 minutes

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

Age Range:
Ages 8 - 14

Resource Types:
Activity, Demonstration, Experiment/Lab Activity, Lesson/Lesson Plan


Materials List (per group of students)

  • Room-temperature water
  • Hot water (colored yellow)
  • Cold water (colored blue)
  • 2 Droppers
  • 2 Clear plastic cups
  • 2 Small cups
  • Water-resistant card
  • 2 Small jars
  • Coffee stirrer, straw, or spoon
  • Paper towels
  • Student Activity Sheet


  • Earth and Space Science
    • Earth Structure
      • Oceans and Water
  • Physical Sciences
    • Heat and Thermodynamics
      • Heat and Temperature
    • States of Matter
      • Liquids
    • Structure and Properties of Matter
      • Volume and Density
  • The Nature of Science
    • The Scientific Process
      • Conducting Investigations
      • Gathering Data


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


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


  • All rights reserved, American Chemical Society, 2007