People's Chemistry Solving People's Problems

Andy S. W. Sae Eastern New Mexico University, Portales, NM 88130

In 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 chem- istry, 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 per~pect ive . '~ We can teach how real-world problems can have chemical solu- tions.

For example:

1. There are two salt shakers; one contains regular salt, and the other contains a salt suhstitute. Which one contains which?

2. 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?

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. The second problem can be

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, en- zyme 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'percep- tion of chemistry, and we must teach our students that chemistry can solve people's problems.

Part of this paper has been presented at the CHEM ED '89 confer- ence 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. -, 7

Chem. Educ. 1988, 65,204.

Deflnlna Problem Performlng Task - Which is table salt and which is salt substitute? (Experlmentatlon)

1. Pulverize salts separately on paper towel with hammer. Deslred Outcome of Solutlon 2. Light torch and adjust flame to almost colorless.

Found out which is salt substitute. 3. Put salt powder close to air intake hole of torch. Analyzing Problem (Observation)

1. Both salts are salty, white, granular. 1. Sample A gives intense yellow flame. 2. There is no label on the shakers. 2. Sample B gives slightly yellow flame. 3. What is the chemical composition of these salts? (Analysis of Data)

Searching for lnformatlon 1. Intense yellow flame shows that Sample A contains sodi- 1. Regular salt is sodium chloride and salt substitute is potas- um.

sium chloride. 2. Slightly yellow flame could be due to impurity in Sample B, 2. Sodium gives brilliant yellow flame; Potassium gives lilac since potassium gives a lilac flame which can be masked

flame. by the blue flame of the torch. Formulating S0l~tlOn(S) Evaluatlon of Outcome

Do a flame test; yellow flame indicates sodium chloride. Sample a has been identified to contain sodium; that means it Gatheilng Tools and Materlals contains sodium chloride and the other salt must be potassium

chloride. Propane torch, matches, hammer, paper towel, suspected salts. 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 Chemical Solutlon Concept

Baby gets wet Use Ultra P a m p n PIUS Polymer. osmosis Night jogging not safe use fluorescent tape Fluoresence Beef t~ tough Use Adolph tenderizer Enzyme catalysis Room cold Turn on gas heater Exothermic reaction

Car battery dead Charge it Oxidation-reduction Rwt in sewer line Use copper sulfate Toxicity Car exhaust pollution Use catalyilc wnverter Catalysis, oxidation Rust stain on blouse Rublcitric acid (aq) Complexing Car grease on skirt Wipe wlh lamp oil Solubility Salt or saii substitute Flame test E m l s s I ~ spectra

Clothes dirty Wash with detergent Solubility Scale In kettle Wash with citric acid Dble replacementldecomp

Clothes dull colored Use Clarox De~omposBon, bleaching Silver dull from Clwox Wash/household Complexing Cut fruit turns brown Soak in Fruit Fresh Oxidation-reduction ammonia Dirty city water in-line purification Filtration, ion-axchange Starch filler In g. beef Use iodine tincture Starchiodine complex

Earring bmksn Use epoxy glue Catalysis. polymerization Stopped up sink Pour in lye, NaOH(s1 Saponlflcatian, solubility Eggs, shoo shelf-life Paint with water glsss Permeability Slpfoam black too big "Cut"1acetone Polymer, solvent Electricity out Light candle Comb~~t ion Sun burn Use sunscreen oil UV absorption

Electricity out Use battery power Oxidation-reduction Tarnished silver Wash/hypo(~iosullate) Compiexing Excess stomach acid Take Alka-Seiher Neutralization Twth decay t m easily Use fluoride toothpaste Chemical equilibrium Garden soil too acidic Add lime Neutralization Twisted ankle o u t d m Use chemical w id pack Endothermic reaction Gdd/lead brick scam Measvemass(Lvo1ume Density Typographical error Use "white O W Solubility, voltatility

HOrs d'w- gets cold Use "canned heat" Exothermic reaction Unmanageable hair Use mausse Polymers. entanglement icy driveway Sprinkle salt Freezing pt. depression Water seeps through Use silicon sealant Vulcanization Iodine stain on shirt Washlhypo (mlosuifate) Oxidation-reduction tiles Lacquer gets too thtck Use lacquer minner Solubility Water damage to deck Paint with water glass Solubility

Lawn not growiw well Use ammonium sulfate Nutrient form nitrogen Windshield frosted Spayldelcer (rr-&anol) Freezing pt. depression Nail polish wmng color Washlpolish remover Salubiiity Worm holes in sweater Use mothballs Volatility, insecticide

896 Journal of Chemical Education