In this activity, learners explore acids and bases by preparing six solutions that combine vinegar and ammonia, ranging from acid (all vinegar) to base (all ammonia). They add an indicator to each solution and compare the resulting colors to those on a pH scale chart. Learners then add drops of ammonia and vinegar to water and indicator, experimenting with the number of drops it takes to change the color of the water. This activity is currently used in the Chemical Reactions Unit in OMSI's Chemistry Lab. Cost estimates are per 100 learners.