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Breathing Blue

Source Institutions

    Community Science Workshop Network

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Breathing Blue

In this activity, learners test exhaled breath for carbon dioxide and learn how to use an indicator as a simple way to measure pH. Learners also explore what happens when an acid (lemon) is mixed with the indicator. This activity can be related to the topic of global climate change. This activity can also be used to discuss atmospheric warming, which is occurring due to increased amounts of carbon dioxide, nitrous oxide, and methane in the atmosphere. [Activity is publicly available through a web crawler capture on]

Quick Guide

Preparation Time:
Under 5 minutes

Learning Time:
10 to 30 minutes

Estimated Materials Cost:
$5 - $10 per student

Age Range:
Ages 8 - 18

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


Materials List (per student)

  • Bromothymol blue solution
  • 2 clear plastic cups
  • 1 straw
  • 1 lemon
  • 1 jar with a lid
  • 1 plastic tray


  • Earth and Space Science
    • Earth Processes
      • Weather and Climate
    • Earth Structure
      • Oceans and Water
      • Atmosphere
  • Life Sciences
    • Cells
      • Chemistry of Life
    • Human Body
      • Respiration
  • Physical Sciences
    • Chemistry
      • Chemical Reactions
      • Acids and Bases
      • Chemistry of Life
      • Solutions
  • The Nature of Science
    • The Scientific Process
      • Conducting Investigations

Informal Categories

  • Nature and Environment


To use this activity, learners need to:

  • see
  • see color
  • touch

Learning styles supported:

  • Involves hands-on or lab activities


Includes alignment to state and/or national standards

This resource is part of:

Access Rights:

  • Free access


  • Mission Science Workshop


  • All Rights Reserved, Mission Science Workshop, ©2013


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