5. Digital media, such as GPS devices or tablet computers, are used Our program’s philosophy is best seen in the following,


multi-part activity. The first part of the activity uses model experiments to understand the curse and blessing of UV radiation.3 It will enable students to answer questions related to the effectiveness of sunscreen, clothing material, and skin types. In the second part, we look at natural sunscreens derived from plants such as horse chestnuts. With an extract of the bark, we take a closer look at the phenomenon of fluo- rescence and we show the dependency on the pH value of the fluorescence dye. Decades of research have shown that an increase in


knowledge does not necessarily lead to a change in behav- ior.4 For this reason, environmental education programs should focus on active and experiential engagement in real- world environmental problems, rather than the transfer of knowledge.5 Issue-based, project-based, and investigation- focused programs in real-world (place-based) nature set- tings will commonly achieve the desired outcomes. Natural Chemistry responds to these findings by actively involving students in the learning process – outdoors!


Alexander Engl has studied chemistry and biology and is currently a Ph. D. student in the Department of Chemistry Education at the University of Koblenz-Landau in Landau, Germany. Björn Risch is a Professor of Chemistry Educa- tion at the University of Koblenz-Landau (Campus Landau). They would like to thank the Fonds der Chemischen Indust- rie (FCI) for funding the project.


Notes


1. Louv, R. (2008). Last Child in the Woods: Saving Our Children From Nature- Deficit Disorder. Chapel Hill: Algonquin Books. ISBN: 978-1-56512-605-3.


2. Engl, A. & Risch, B. (2014). CHEMIE PUR: Unterrichten im Freiland mit Naturstoffen. Eine interaktiv experimentelle Bodenrallye. Naturwissenschaften im Unterricht Chemie, 144(6), 34-37.


3. Jahnel, C., Jung, P. & Risch, B. (2014). Sonne(n)mit Verstand – Modellex- perimente zum Thema „UV-Strahlung und Sonnenschutzmittel“. Naturwissen- schaften im Unterricht Chemie, 144(6), 28-33.


4. Roczen, N. (2011). Environmental competence. The interplay between con- nection with nature and environmental knowledge in promoting ecological behavior. Eindhoven: University of Technology Library. ISBN: 978-90-386- 2950-6.


5. Stern, M. J., Powell, R. B. & Hill, D. (2014). Environmental education program evaluation in the new millennium: what do we measure and what have we learned? Environmental Education Research, 20(5), 581-611. DOI: 10.1080/13504622.2013.838749.


Activities 1. Sunscreen in a Model Experiment


Activities 2 and 3 can be found at http://greenteacher.com/natural-chemistry-outdoors/ papers in the shoe box until required.


Part A: Production of photo-sensitive cyanotype filter paper The photo-sensitive cyanotype filter paper displays UV radia- tion by changing color. This demonstrates the powerful effect of UV radiation. Follow these instructions to create some for the experiment. Materials: Beaker (50 mL), graduated cylinder (50 mL),


glass rod, petri dish (≥ 7 cm), tweezers, 5 regular filter papers (≥ 7 cm), shoe box, paper towels, safety gloves, waste container Chemicals: 2.5 g green ammonium ferric (III) citrate, 1 g


potassium ferricyanide (III), distilled water Time: 10 minutes Safety instructions: Wear latex safety gloves to prevent your skin from being stained blue.


Procedure a. Put on latex safety gloves. b. Using the graduated cylinder, measure 25 mL of distilled water.


c. Place the 50 mL beaker in the shoe box to avoid as much UV radiation as possible.


d. In this beaker, prepare 1 g potassium ferricyanide (III) and 2.5 g green ammonium ferric (III) citrate in 25 mL of distilled water.


e. Mix beaker chemicals with a glass rod. f. For best results, place the petri dish inside the shoe box beside the beaker for the next steps to keep it shaded or place it on the counter beside the box.


g. Pour part of the solution from the beaker into a petri dish and put all five filter papers in the dish to soak up the poured solution.


h. Using the tweezers, lift the filter papers from the petri dish and pat the filter papers dry using paper towels. i. Remove the beaker from the shoe box and store the filter


Page 40


2. Reduction: Fe3++ e- → Fe2+ The resulting ferric (II) ions in chemical equation (2) react


with the potassium ferricyanide (III) to form Prussian blue. The simply oxidized citrate radical releases a second electron and forms acetonedicarboxylic acid due to decarboxylation.


GREEN TEACHER 109


j. Expose one of the five filter papers to UV radiation from the sun. You can also cut a small paper template to put over the exposed filter paper to show the difference between the fully exposed and covered portions.


k. Leave the remaining papers in the shoe box. Disposal: Collect the remaining solution in the beaker and


petri dish and the one UV exposed filter paper to place in a waste container. (Hold onto the other four filter papers, for later use, as mentioned below.) Explanation: The basis for these sunscreen experiments is


the cyanotype process, which involves a photochemical-induced reaction between ammonium ferric (III) citrate and potas- sium ferricyanide (III) (red prussiate). If a watery solution of the two chemicals is exposed to sunlight (or an alternative source of UV radiation such as an ultraviolet lamp, overhead projector etc.), a distinctive blue color forms within a minute. Exposure to high-energy UV radiation causes an electron of the citrate ligand (from the ammonium ferric (III) citrate) to be transferred to the ferric (III) ion of the ammonium ferric (III) citrate, which is in turn reduced to a ferric (II) ion:


1. Oxidation:


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52