Changing Planet: Ocean acidification – The chemistry is less than basic!

Summary: Students will use a pH indicator solution to detect the presence of carbon dioxide and changes in acidity, and to model ocean-atmosphere interactions.

Source: Adapted by NESTA/Windows to the Universe team members Missy Holzer, Jennifer Bergman, and Roberta Johnson from the Carbon Dioxide Sources and Sinks activity on Windows to the Universe.

Time: This activity requires careful preparation including some set-up the previous day. It is recommended that the directions be read carefully before beginning this activity.

  • Materials preparation: 40 minutes
  • Class time: 40 minutes
  • Discussion and review: 30 minutes

Student Learning Outcomes

  • Students will be able to explain the concept of ‘sources’ and ‘sinks’ as they relate to carbon dioxide.
  • Students will understand the use of an indicator solution (BTB) to reveal the presence of carbon dioxide as well as levels of acidity.
  • Students explain the cause and effect relationship between lower pH levels of seawater and carbonate ion availability for shell formation in marine organisms.

Lesson format: Laboratory Experiment

National Standards Addressed:

  • National Science Content Standards 5-12: Abilities necessary to do scientific inquiry
  • National Science Content Standard 5-8: Properties of Earth materials
  • National Science Content Standards 9-12: Geochemical Cycles
  • National Science Content Standards 9-12: Environmental Quality


For each four-student team

  • Five test tubes
  • Test tube rack
  • One hole stopper with tubing attached
  • Baking soda
  • Vinegar
  • Aluminum foil
  • Cotton balls
  • Bottle of BTB solution (bromothymol blue)
  • Straws
  • Sprig of Elodea (available in pet stores)
  • Masking tape
  • Markers
  • Distilled water
  • 250 mL beaker or plastic cup
  • graduated cylinder
  • coral and shell specimens
  • pH indicator solution (from an aquarium test kit)

Missy Holzer, Windows to the Universe, 3 March 2011. More information.

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OA-ICC Highlights

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