In this Activity, students test the pH and acid neutralizing capacity of plain water, water that they blow their breath into, and water with either baking soda or lemon juice added. Students discover why normal rain is not neutral when they observe the effect of their breath on the pH of poorly buffered water. The observation that clean, natural rain is not neutral can be used as an example of equilibrium or to introduce weak acids. The primary concept introduced by this Activity is that of buffering capacity.
Halstead, J. A.; 1997, 74, 1456A.