Floral pigments as litmus solutions
Laboratory thirteen in physical science had the students collect flowers from around campus, produce floral solutions by boiling in water, and then test to see which floral solutions changed color for both a known acid and a known base. Teaching in the tropics makes this laboratory possible in both November and April, or even in July.
Lupe with a floral solution that turns green in the presence of a base, magenta in the presence of an acid.
This laboratory remains a favorite of the students. This term six of thirty-two picked laboratory thirteen as their favorite laboratory. Only one student chose thirteen as their least favorite laboratory. In the tropics we are blessed with many different flowers and colored leaves to try. For those in temperate climates, Fred Senese covers some of the options available. Senese also notes that onions and vanilla are olfactory pH indicators.