Hot and Cold

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In this chemistry challenge, learners discover that many chemical reactions involve heat loss or gain. With this understanding, they try to find a combination of chemicals that could be used to make an instant cold pack. They are given baking soda, ammonium nitrate, calcium chloride, and potassium chloride, along with vinegar and water (3% hydrogen peroxide and yeast can also be used). Learners combine chemicals into calorimeters, then use thermometers to measure how the temperature changes. Calorimeters can be made by pushing a heated test tube into home insulation foam (instructions in PDF) or can be purchased (one source is Flinn Scientific). The water and ammonium nitrate, and vinegar and baking soda, are candidates for making a cold pack.

Quick Guide

Preparation Time:
30 to 45 minutes

Learning Time:
10 to 30 minutes

Estimated Materials Cost:
$10 - $20 per group of students

Age Range:
Ages 4 - 14

Resource Types:
Activity, Experiment/Lab Activity


Materials List (per group of students)

  • 5 small non-mercury thermometers
  • 2 washing bottles containing vinegar ( 5% acetic acid)
  • 2 washing bottles containing water
  • 1 liter water
  • 500 ml vinegar
  • Baking soda (NaHCO3), ammonium nitrate (NH4NO3), anhydrous calcium chloride (CaCl2), potassium chloride (KCl)
  • 20 plastic Dixie cups (or small wide mouth container) for solid chemicals
  • 20 Popsicle sticks, small plastic spoons, or Beral pipettes
  • 5 calorimeter strips (see below)
  • Paper towels for spills
  • A container of clean water
  • A safe container to dump solutions into and seal (waste container)
  • Either small-scale calorimeters from Flinn, or
  • 8 2x2x8 inch strips of insulation foam
  • 22-mm diameter glass test tube
  • Heat gun or hair dryer


  • Physical Sciences
    • Heat and Thermodynamics
      • Heat and Temperature
      • Heat Transfer
      • Thermodynamics and Entropy
    • Chemistry
      • Chemical Reactions
  • The Nature of Science
    • The Scientific Process
      • Conducting Investigations
      • Gathering Data

Informal Categories

  • Science Festivals Activity
  • Sports and Exercise


To use this activity, learners need to:

  • see
  • see color
  • read
  • touch

Learning styles supported:

  • Uses STEM to solve real-world problems
  • 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