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Cool It!

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    Oregon Museum of Science and Industry

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Cool It!

Learners make a refrigerator that works without electricity. The pot-in-pot refrigerator works by evaporation: a layer of sand is placed between two terra cotta pots and thoroughly soaked with water. The contents of the inner pot are covered with a wet cloth. As the water evaporates, it cools the contents. If more water is added, the cooling can be maintained for some time. The lesson plan includes handouts, background information, and suggested extension activities.

Quick Guide

Preparation Time:
30 to 45 minutes

Learning Time:
45 to 60 minutes

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

Age Range:
Ages 11 - 14

Resource Types:
Activity, Lesson/Lesson Plan


Materials List (per group of students)

  • 2 large clay pots (flower pots work well)
  • 2 clay pots small enough to fit in the larger pots with some space between them
  • Sand or fine gravel
  • 2 pieces of cloth large enough to cover the large pots (Make sure they’re both the same type. Felt, cotton, and canvas work well.)
  • 2 small containers with lids that can fit in the small pot (Baby food jars or film canisters work well.)
  • Plastic bottles (Water bottles with pop-up lids work well.)
  • Water
  • 2 small pieces of cardboard or cardstock
  • Two thermometers
  • Scissors
  • Materials to photocopy: Student Background and Student Procedure (1 per group)
  • Optional: One or two fans for the class


  • Earth and Space Science
    • Earth Structure
      • Oceans and Water
  • Engineering and Technology
    • Technology
      • Energy and Power
  • Physical Sciences
    • Heat and Thermodynamics
      • Heat and Temperature
      • Heat Transfer
    • Energy
      • Energy and Power
    • States of Matter
      • Liquids
      • Gases
      • Changes of Phase
  • The Nature of Technology
    • The Design Process
      • Invention and Innovation


To use this activity, learners need to:

  • see
  • read
  • touch

Learning styles supported:

  • Involves teamwork and communication skills
  • Involves hands-on or lab activities


Includes alignment to state and/or national standards

Access Rights:

  • Free access



  • All Rights Reserved, OMSI, ©2006

Funding Source:

  • NASA


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