Approximately one quarter of carbon dioxide emitted by humans in the air is absorbed by the ocean. This alters the chemical composition of the sea: a more acidic water threatens the life conditions of organisms whose skeletons or cells are made of calcium carbonate, such as phytoplankton, snails, mussels or, more evident to the human eye, corals. In order to explain children how Ocean Acidification works, we used red cabbage juice, a safe acid/base indicator which reacts in a clear manner to the introduction of CO2 by changing colour.
The star of the show was some red cabbage juice. We poured a very small volume of the cooled juice into test tubes and we asked children to blow through a drinking straw repeatedly for a few minutes until they could see the cabbage juice turn noticeably pinker that the juice in the bottle.
What has happened? The carbon dioxide in the breath combined with the water in the cabbage juice (cabbage is an acid indicator) to form carbonic acid, causing the pH of the solution to drop and the cabbage juice to turn pink.
Why this is interesting? About a quarter of the carbon dioxide released by activities like burning fossils fuels is absorbed by oceans and as a result the ocean water becomes more acidic, like the cabbage juice in the experiment.
Our simple experiment was particularly successful; the children and some of their teachers too, had a lot of fun blowing into the cabbage juice and after the experiment they told us that they now have a better understanding of what ocean acidification is and why it is important.
It was great a experience for us all, as well. The experiment stimulated the imagination of the young students and during the lively discussion afterwards they were able to offer us some out of box thinking and we came up with some rather pioneering ideas and innovative solutions of how to combat ocean acidification.
ParticipantsEleni Angnostou Graeme MacGilhrist Migue Martínez-Botí Athena Drakou
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