Today we began a three-day experiment called “Mystery Liquids.” Students began designing their own lab with the goal of classifying ten mysterious liquids as acidic, basic, or neutral. They needed to use what we learned yesterday (characteristics of acids & bases, the PH scale, acid/base reactions, etc.) to design an experiment that would allow them to identify each of the liquids.
The catch is that their grade will be, in part, determined by their use of PH strips. Simply testing the PH of all ten liquids would be too easy; the highest that could earn them would be a B+. If they agree to only use five PH strips, they can earn an A. If they only use one PH strip, then they can earn an A+. Their challenge will be to classify some of the liquids using other means. That could be through observation, or reaction tests, or perhaps a mix of the two.