JCE Classroom Activity: #21
Instructor Side
Hunting for Chemicals in Consumer Products by Arthur M. Last, Univ. College of the Fraser Valley, Abbotsford, BC V2S 7M9, Canada
Integrating the Activity into Your Curriculum Although many textbooks mention the uses of a few selected compounds, such references are often incidental and may frequently be overlooked by students. Few textbooks devote any space to a full discussion of the use of chemicals in consumer products and this practical application of chemistry often remains unaddressed in courses at both the high school and college levels. This activity is intended to increase student awareness of the presence of a variety of chemical compounds in a range of common consumer products.
fold here and tear out
About the Activity This activity is adapted from a longer, more complex “Consumer-Chemical Hunt” included in this issue (1). The activity might be given to students toward the conclusion of an introductory chemistry course. (As an alterative, it could be introduced earlier in the year as an ongoing project with the instructor referring to specific clues at appropriate points in the curriculum.) Students will need to be able to locate numerical data, e.g., pKa and Ksp values, either in their textbooks or in a standard chemistry reference book, so it is probably best for the students to determine the identity of the compounds in the classroom. It may be helpful to have students work together in small groups. After identifying the compounds, the search for consumer products may be assigned as a take-home activity. Finally, students can prepare a display or poster about one of the chemicals, or about the chemicals in one product, and present it to the class.
Answers and Hints The table below includes answers, hints, comments about other compounds that students may identify, types of products that contain each compound, and at least one product brand name, in parentheses. Note that it is preferable to have students identify products using brand names, as this simplifies the verification process. (Editor’s Note: All brand name products were located in a supermarket or discount store in Madison, WI.) Name
perforated
Formula
Hints
Products
1.
calcium carbonate; calcite
CaCO3
tables of solubility product constants (K sp for BaCO3 may be similar in some tables)
antacids (Tums); calcium supplements
2.
phosphoric acid
H3PO4
properties of common mineral acids (H3PO3, H3AsO4, and H3AsO3 are less common)
soft drinks (Coca Cola, Pepsi)
3.
magnesium sulfate heptahydrate; Epsom salts
MgSO4.7H2O
list of magnesium compounds in a handbook (other heptahyrates of Mg compounds are not common)
laxative; soaking agent (Swan)
4.
sodium fluoride
NaF
5.
sodium phosphate; TSP
Na3PO4
qualitative analysis or reactions of common ions
6.
sodium hypochlorite
NaClO
oxidation numbers, common oxyanions (any hypochlorite—sodium hypochlorite is common)
7.
hydrogen peroxide
H2O2
8.
ammonium sulfate
(NH4)2SO4
9.
potassium iodide
KI
10.
iron(II) sulfate; ferrous sulfate
FeSO4.H2O
electron configuration, reactions of common ions (4, 5, and 7 hydrates also exist)
plant nutrient; pet foods (Alpo, Friskies) moth repellent; deodorizers (Enoz)
electron configurations and electronegativity
cleaning products (Cascade dishwasher detergent) bleach (Clorox)
structures of binary compounds
antiseptic– 3% H2O2 (Swan); hair-color lightener (L'Oreal)
qualitative analysis or reactions of common ions
fertilizer (Miracle Grow for Tomatoes, Garden Basics)
ionization energy, electron affinity
iodized table salt (Morton)
11.
1,4-dichlorbenzene; paradichlorobenzene
C6H4Cl2
empirical formula from percentage composition; molecular formula from empirical formula and molecular mass; handbook to obtain names of compounds; polarity of molecules
12.
acetic acid
HC2H3O2
table of K a or pK a values of common acids
p-dichlorobenzene;
toothpaste (Crest, Colgate)
vinegar (Heinz)
Citations and Additional References 1. Last, A. M. J. Chem. Educ. 1999, 76, 1503–1504. 2. Selinger, B. Chemistry in the Market Place, 4th ed.; Harcourt Brace Jovanovich: Sydney, Australia, 1989. 3. Emsley, J. The Consumer’s Good Chemical Guide; Freeman: New York, 1994.
This Activity Sheet may be reproduced for use in the subscriber’s classroom. JChemEd.chem.wisc.edu • Vol. 76 No. 11 November 1999 • Journal of Chemical Education
1504A
JCE Classroom Activity: #21
Student Side
Hunting for Chemicals in Consumer Products by Arthur M. Last, Univ. College of the Fraser Valley, Abbotsford, BC V2S 7M9, Canada Many people use a wide variety of consumer products each day without giving any thought to the chemicals that are responsible for providing the properties that make these products useful. Similarly, people rarely consider the chemicals that may have been added to a product in order to improve its properties, e.g., to extend the shelf life or to improve the taste of a food product. The purpose of this activity is to increase your awareness of the specific compounds that are present in various consumer products and to determine the reason for their presence.
Try This Listed below you will find clues to the identities of 12 chemical compounds, each of which is present in at least one common consumer product. Use your textbook and other references (see below) to assist you in determining the identity of each chemical. If more than one chemical fits the clue, make a note of the possibilities, then decide which is the most common (has a common name—perhaps something you have heard of—or is used as an example in your textbook) and proceed with that compound. Write the name and chemical formula of each compound. After identifying the chemicals, find a consumer product in which each compound is present. Good places to begin looking would be your kitchen and bathroom. Visits to a supermarket, discount store, drugstore, and garden center might also be productive. The numerical data included in the clues were obtained from The Handbook of Chemistry and Physics (1). Your textbook or other reference books may give slightly different values. Clues
An insoluble group 2 metal salt with a Ksp of 4.96 × 10-9 at 25 °C. A triprotic inorganic acid containing an element from group 15 of the periodic table. A heptahydrate salt of the element whose nucleus contains 12 protons. An ionic compound with isoelectronic anions and cations. The anion is formed by the most electronegative element. __ 5. A salt that contains four ions per formula unit, imparts a yellow color to a Bunsen flame in the so-called “flame test”, and reacts with silver nitrate solution to give a precipitate that is soluble in both aqueous ammonia and nitric acid. __ 6. A salt containing an oxyanion in which chlorine is in the +1 oxidation state. __ 7. An inorganic compound containing an oxygen–oxygen single bond. __ 8. A compound that would release a basic gas when it is heated with aqueous sodium hydroxide and would give a precipitate with a 1:1 ion ratio when added to aqueous barium chloride. __ 9. A binary ionic compound formed between the element with the lowest first ionization potential in period 4 of the periodic table and the element with the most negative electron affinity in period 5. __ 10. A hydrated salt containing a divalent transition-metal ion with six 3d electrons and the same anion as unknown 8. __ 11. A nonpolar aromatic compound with a molar mass of 147.01 g/mol and the following percentage composition (by mass): 49.02% carbon, 2.73% hydrogen, and 48.23% chlorine. __ 12. An organic acid whose pKa is 4.76 at 25 °C. __ 1. __ 2. __ 3. __ 4.
Additional Activities
__ 1. After you have identified the chemicals and found examples of consumer products in which they are ingredients, try to find the reason for their presence in the products. __ 2. Select one of the compounds and prepare a poster or display and short oral presentation describing the compound, its properties, and uses. As an alternative, your instructor may suggest that you select an interesting consumer product that contains a number of chemicals and ask you to prepare a poster or display and short oral presentation describing each of the chemicals present and explaining their roles in the product.
Information Sources 1. CRC Handbook of Chemistry and Physics, 76th ed.; Lide, D. R., Ed.; CRC: Boca Raton, FL, 1995. 2. Lewis, G. R. 1,001 Chemicals in Everyday Use, 2nd ed.; Wiley: New York, 1999. 3. The Merck Index, 11th ed.; Budavari, S., Ed.; Merck: Rahway, NJ, 1989.
From the World Wide Web
(all sites accessed September 1999)
1. Quia! Matching Game–Common Chemicals. http://www.quia.com/custom/3021gate.html 2. Common Chemicals in Your Home. http://www.mbnet.mb.ca/~cherylp/curricul/sc20s/appendix/app311.htm
This Activity Sheet may be reproduced for use in the subscriber’s classroom. 1504B
Journal of Chemical Education • Vol. 76 No. 11 November 1999 • JChemEd.chem.wisc.edu
