About This Lesson
This lesson should be taught near the beginning of an ocean acidification unit to give students a basic understanding of pH,
acids, bases, and the pH scale. Students will use a natural acid-base indicator made from red cabbage to investigate the pH of several familiar liquids. As the indicator reacts with liquids of different pH values, students will observe a range of colors and arrange their samples to create a "rainbow of pH." The activity provides students with the background knowledge needed to understand how scientists use pH to measure changes in ocean chemistry and why a seemingly small change in ocean pH can be important. Teacher supervision is required. Students should wear safety goggles during the investigation and should not taste any of
the materials.
