What is pH and how does carbon dioxide released from the burning of fossil fuels increase the acidity of the ocean? Students explore the answers to these questions in this two-part lab investigation. Students first investigate the power of pH by creating their own pH scale through a serial dilution of hydrochloric acid and sodium hydroxide. Students then compare the pH of fresh water and sea water and add carbon dioxide to observe how pH is affected. Finally, the effect of ocean acidification on marine life is observed through the use of calcium carbonate powder and hydrochloric acid.