Blowing into the cabbage solution changes the color, indicating the formation of acid.
When carbon dioxide (CO2) in the atmosphere is absorbed by seawater, chemical reactions occur that reduce seawater pH, making it more acidic. This process is known as ocean acidification and it poses a serious threat to shell-building sea life and corals, because it make it harder for them to build and maintain their shells.
Recently we learned of a safe, simple CO2 Breath Test using red cabbage juice to help students visualize how excess CO2 in the atmosphere contributes to ocean acidification.
The procedure is described in detail on the Kitchen Pantry Scientist blog.
This demonstration makes a great companion to our recently release curricula, Nature-Inspired Chemistry: Concrete Without Quarries. Because the production of conventional concrete (mining and heat treating limestone) is a significant source of CO2 emissions, which impact coral, presenting the two experiments together creates space for a rich dialog about cause and effect and complex systems.
