People's Chemistry Solving People's Problems Andy S. W. Sae Eastern New Mexico University, Portales, NM 88130 I n my 20 years of teaching chemistry to nonscience majors and elementary presemice teachers, I have found that most of my students come with a preconceived notion that chemistry, as a department, is for the elitists; as a discipline, it is abstract and mathematical, as a body of knowledge, it is irrelevant to nonchemists; as a science, it is a mere collection of facts; as a technology, it is the cause of explosion and pollution and the origin of toxic waste dumps. T o change people's perception of chemistry, we must teach people's chemistry instead of chemists' chemistry.' ~ People's chemistry uses a real-world p e r ~ p e c t i v e . ' We can teach how real-world problems can have chemical solutions. For example:
solved using complex formation of ferric ions with carboxylic acids by rubbing wet citric acid on the m s t stain. The third problem can be solved by sprinkling Fruit Fresh on the apple slices; it demonstrates concepts of oxidation-reduction, enzyme catalysis, and the application of chemistry in consumer products. The table shows a list of examples of real-world problems encountered by chemists and nonchemists alike and their chemical solutions. As the world faces bigger and more complex problems such as toxic waste dumps, acid rain, ozone depletion, and the greenhouse effect, we must change our students'perception of chemistry, and we must teach our students that chemistry can solve people's problems.
1. There are two salt shakers; one contains regular salt, and the
other contains a salt suhstitute. Which one contains which? There is some rust stain on a light-colored blouse. How do you remove it? 3. Apples slices turn brown after they have been cut. How do you prevent them from tnrning brown? 2.
The process of problem-solving and the solution to the first oroblem is eiven in the fieure. Both chemistry majors and ionchemist;; majors can find relevance in studying the flame emission in this example. T h e second problem can be
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Deflnlna Problem Which is table salt and which is salt substitute? Deslred Outcome of Solutlon Found out which is salt substitute. Analyzing Problem 1. Both salts are salty, white, granular. 2. There is no label on the shakers. 3. What is the chemical composition of these salts? Searching for lnformatlon 1. Regular salt is sodium chloride and salt substitute is potassium chloride. 2. Sodium gives brilliant yellow flame; Potassium gives lilac flame. Formulating S0l~tlOn(S) Do a flame test; yellow flame indicates sodium chloride. Gatheilng Tools and Materlals Propane torch, matches, hammer, paper towel, suspected salts.
Part of this paper has been presented at the CHEM ED '89 conference at Kingston, ON, Canada, August 13-18, 1989. I Bucat, R. 6.; Code, A. R. H. J. Chem. Educ. 1988,.65, 777. 'IJsing Reai-World Examples in the Teaching of Chemistry-A Symposium", J. Chem. Educ. 1983,60, 1031. Sae, A. S. W. J. Chem. Educ. 1986, 63, 56. "Svm~osia on Critical Thinkina and Consumer Chemistry", J. -, Chem. Educ. 1988, 65,204. 7
Performlng Task (Experlmentatlon) 1. Pulverize salts separately on paper towel with hammer. 2. Light torch and adjust flame to almost colorless. 3. Put salt powder close to air intake hole of torch. (Observation)
1. Sample A gives intense yellow flame. 2. Sample B gives slightly yellow flame. (Analysis of Data)
1. Intense yellow flame shows that Sample A contains sodium. 2. Slightly yellow flame could be due to impurity in Sample B, since potassium gives a lilac flame which can be masked by the blue flame of the torch. Evaluatlon of Outcome Sample a has been identified to contain sodium; that means it contains sodium chloride and the other salt must be potassium chloride.
Problem Solved
tlving me low-sodium problem.
Volume 67 Number 10 October 1990
895
Real-World Layperwns' Problems and Chemical Solutions PTDblem
Chemical Solution
Concept
Problem
Baby gets wet Beef t~ tough Car battery dead Car exhaust pollution Car grease on skirt Clothes dirty Clothes dull colored Cut fruit turns brown Dirty city water Earring bmksn Eggs, shoo shelf-life Electricity out Electricity out Excess stomach acid Garden soil too acidic Gdd/lead brick scam HOrs d'wgets cold icy driveway Iodine stain on shirt Lacquer gets too thtck Lawn not growiw well Nail polish wmng color
Use Ultra P a m p n PIUS Use Adolph tenderizer Charge it Use catalyilc wnverter Wipe w l h lamp oil Wash with detergent Use Clarox Soak in Fruit Fresh in-line purification Use epoxy glue Paint with water glsss Light candle Use battery power Take Alka-Seiher Add lime Measvemass(Lvo1ume Use "canned heat" Sprinkle salt Washlhypo (mlosuifate) Use lacquer minner Use ammonium sulfate Washlpolish remover
Polymer. osmosis Enzyme catalysis Oxidation-reduction Catalysis, oxidation Solubility Solubility De~omposBon,bleaching Oxidation-reduction Filtration, ion-axchange Catalysis. polymerization Permeability Comb~~tion Oxidation-reduction Neutralization Neutralization Density Exothermic reaction Freezing pt. depression Oxidation-reduction
Night jogging not safe Room cold R w t in sewer line Rust stain on blouse Salt or saii substitute Scale In kettle Silver dull from Clwox
896
Solubility
Nutrient form nitrogen Salubiiity
Journal of Chemical Education
Chemical Solutlon
use fluorescent tape Turn on gas heater Use copper sulfate Rublcitric acid (aq) Flame test Wash with citric acid Wash/household ammonia Starch filler In g. beef Use iodine tincture Stopped up sink Pour in lye, NaOH(s1 Slpfoam black too big "Cut"1acetone Use sunscreen oil Sun burn Tarnished silver Wash/hypo(~iosullate) Twth decay t m easily Use fluoride toothpaste Twisted ankle o u t d m Use chemical w i d pack Typographical error Use "white O W Unmanageable hair Use mausse Water seeps through Use silicon sealant tiles Water damage to deck Paint with water glass Windshield frosted Spayldelcer (rr-&anol) Worm holes in sweater Use mothballs
Concept Fluoresence Exothermic reaction Toxicity Complexing E m l s s I spectra ~ Dble replacementldecomp Complexing Starchiodine complex Saponlflcatian, solubility Polymer, solvent UV absorption Compiexing Chemical equilibrium Endothermic reaction Solubility, voltatility Polymers. entanglement Vulcanization Solubility Freezing pt. depression Volatility, insecticide
