Inquiry With Acids And Bases

Inquiry with anything is modified for use with indicators. This still allows the student to define the question, set the procedure, collect and report on results. Included is a reflective piece and how student work is tied to the nature of science. See http://www.wetheteachers.com/plan.php?id=37 for a discussion of general technique used to produce this activity and others like it.

Things I have tried that students can use as a springboard to their own investigations of pH indicators. As a side note, does anyone know what is a possible advantage to a plant to have a pH indicator built Hydrangea color depends in part on soil pH. Bluebonnets and morning glory flowers are pH indicators. Plain tea and Red Zinger tea also work.


For the morning glory vine flower I have noticed that if I damage the blue petal the flower will turn red along the damaged edge. I assume that the plant is releasing a bit of acid.

We have a morning glory tree. The flower is blue in the morning and turns pink as the day heats up. Again I assume this is due to a pH change, but I am not certain.
Lavender tree Vitex agnus castus. The blue flowers are indicators.

Extracting indicators Red cabbage juice is a pH indicator. Cut up the cabbage and boil about 10 minutes the resulting solution will provide enough for many classes. Alternate method You can also chop up the cabbage add a little water and blend in a blender. Strain the mixture and the remaining liquid is the same as boiling. You can apply these techniques to other things and test the results.

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