When was the last time you thought about paper? Really thought about it. Even before the shift to a digital age, with a push to go paperless, it was somewhat a throwaway, unnoticed material. But, it is one rich in chemistry. For 2019 Chemists Celebrate Earth Week (CCEW), the American Chemical Society’s chosen theme encourages us to “Take Note” of it and its chemistry.
The article Demonstration Extension Based on Color-Changing Goldenrod Paper (available to JCE subscribers) in the February 2019 issue of the Journal of Chemical Education helps readers do just that. Color-changing goldenrod paper and its associated demonstrations like hidden messages and the bloody handprint have been around for quite some time. However, the paper, with its special dye, was not readily available to buy for a period of time. It is now back and available (Educational Innovations is one supplier), and authors Schorr and Campbell point out several extensions to past demonstrations related to this special paper.
In addition to the most often seen yellow to red color change, when ammonia or another base is sprayed on the paper, they highlight other changes, such as a change to purple-black when 3 M hydrochloric acid is used, or a whitish color with bleach. Figure 2 from the article highlights a possible way to showcase this goldenrod range of possibilities, using paper flowers dipped in (left to right) 3 M HCl, undipped, sodium carbonate solution, household bleach. The containers in front tie in with a more in-depth discussion by the authors of a specific dye compared to curcumin, which can be used to make a do-it-yourself color-changing paper.
Figure 2 – Reprinted with permission from Demonstration Extension Based on Color-Changing Goldenrod Paper, Donald K. Schorr and Dean J. Campbell. Journal of Chemical Education, 96 (2), 308-312. Copyright 2019 American Chemical Society.
Along the way, the authors make note of other paper-based chemistry that can be done without the special goldenrod paper. This includes an additional color change, when iodine solution on many papers changes from brown-yellow to blue-black, due to the presence of starch-based compounds. Students could also explore the bubbling reaction mentioned by the authors, when copier paper was placed in hydrochloric acid. I experimented with strips of paper, taped onto pencils and suspended over clear, colorless glasses. With tap water in one and white household vinegar in another, the bubbling action was obvious with the vinegar. The bubbles even lifted the paper strip in the glass. Larger bubble pockets were visible within the strip. Calcium carbonate is a common filler used in paper, to help make the paper more opaque and brighter, while being less expensive than cellulose.
More from the February 2019 Issue
Want more color-changing chemistry? Look to Mary Saecker’s category “Investigating Acid–Base Chemistry” in her post JCE 96.02 February 2019 Issue Highlights. You’ll find an experiment that links homemade fermented foods with pH changes described in Exploring Acid–Base Chemistry by Making and Monitoring Red-Cabbage Sauerkraut: A Fresh Twist on the Classic Cabbage-Indicator Experiment.
What else have you used from the Journal in your classroom? Share! Start by submitting a contribution form, explaining you’d like to contribute to the Especially JCE column. Then, put your thoughts together in a blog post. Questions? Contact us using the ChemEd X contact form.