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Science presenter Jon Chase uses universal indicator to measure the pH of a solution. The pH of the oceans is slightly alkaline but the increase in carbon dioxide in the atmosphere is acidifying them. This is demonstrated in the lab by adding dry ice to an alkaline solution containing universal indicator and explaining the pH changes.
This clip is from:
First broadcast:
11 May 2012

Classroom Ideas

Students could test the pH of fresh and sea water from different sources, both using universal indicator and a pH probe. Sea water could be taken from a nearby coastline, or mixed up using synthetic salt mix available from aquatic retailers. As an alternative to the demonstration using dry ice, this could be repeated with universal indicator and water in a conical flask with a student exhaling into it slowly through a straw (wearing eye protection). The effect of ocean acidification on coral reefs could be researched and investigated using calcium carbonate in the lab.