In the Laboratory
Scientific–Chemical Viewpoints Regarding Smoking: A Science Laboratory for All Ron Blonder Department of Science Teaching, The Weizmann Institute of Science, Rehovot 76100, Israel;
[email protected] Chemists examine the world from a perspective of chemical processes and compounds. In order to expose high school students to the chemists’ world, we designed a laboratory activity that deals with cigarette and water pipe smoking. We chose smoking for two reasons: First, smoking is relevant to adolescents and, therefore, an example of a subject that is really a “need-to-know” issue for the students. Second, smoking cigarettes and water pipes relates to (and is based on) several aspects of chemistry (1) and, thus, serves as a meaningful way to encourage adolescents to learn chemistry while experimenting in the laboratory. Adolescents experience smoking in two different dimensions: on the one hand smoking is a symbol of maturity, yet on the other hand exposure to tobacco smoke is a major cause of human mortality throughout the world. In this laboratory activity we provide some scientific tools to examine smoking. Since the social data regarding smoking are well-known, students know that the exposure to tobacco smoke is estimated to contribute to about 440,000 deaths annually in the United States alone (2). Smoking is a risk factor for numerous illnesses (3–8), among them are various malignancies, chronic obstructive lung disease, coronary artery disease, and stroke. However, the scientific aspects of smoking, for example, the chemical processes and components of smoke, are not known to them. This activity examines the chemical process and the components of smoke, of both cigarettes and water pipes (narghiles1 also known as “hookah”). As science educators our main goal in this activity is to show the relevance of chemistry to the life of adolescents and in addition to influence students’ attitude towards cigarettes and water pipe smoking. The later assumption is based on the belief that knowledge and evidence can change health patterns (9). Cigarettes and Water Pipes: The Chemical Aspects The laboratory activity focuses on smoking, both cigarettes and water pipes, from a scientific point of view. This laboratory gives an opportunity to expose high school students to the relevance of chemistry to their lives by analyses of cigarette and narghile smoke. There are four activity stations in the laboratory:
1. The acidity of the smoke.
2. Solid particles in the smoke.
3. Vapor phase substances in the smoke.
4. Simulating the effects of smoking on lungs.
Each activity lasts 30 to 45 minutes. At each station a different topic in chemistry or biology is emphasized. This method introduces the students to a wide range of scientific subjects with special emphasis on chemistry and to introduce the students to the dangers associated with smoking from a scientific viewpoint. We describe each station 248
at three levels, the experimental procedure, the results, and the chemistry that is introduced through the station (a more detailed description is given in the online material). Experimental Procedure and Results Station 1: Acidity of Smoke At the first station the students measure the acidity of cigarette smoke. Determining the pH is done by adding a pH indicator to each solution. Bromothymol blue is used. Bromothymol blue is blue at pH > 7.1, green at the range 7.1 > pH > 6.2, and yellow at pH < 6.2 (pKa = 7.1). After a short introduction about acids, bases, and indicators, the students build a “smoking machine” as shown in Figure 1. The smoke from one cigarette is bubbled through the indicator solution, and a change in the solution’s color can be observed. The color changes from deep blue to green, indicating a change in acidity caused by the cigarette smoke. Advanced students (who are typically chemistry majors) also measure the pH with a potentiometer after the smoking operation and obtain a pH value of 6.2. After the experiment, the students discuss the possible effects of acidity on the smoker’s tissues that come in direct contact with the cigarette’s smoke. The pH of the lung tissue is 7.4. Some students raise questions regarding the effect of number of smoked cigarettes on the pH and some of the groups investigate this question. Station 2: Solid Particles in Smoke At the second station the students collect the solid particles from cigarette and narghile smoke and compare them. They learn about the solid-state phase, and we mention the concept of small, solid particles (colloids) in the smoke. They build a “smoking machine”, shown in Figure 2, to collect the solid particles from the smoke. The narghile and cigarette smoke is pumped through a filter paper to collect solid particles from the smoke. This station enables the students to make a qualita-
water aspirator
pH indicator
Figure 1. A “smoking machine” in which the smoke of one cigarette is bubbled through the indicator solution. This setting allows the student to estimate the acidity of the cigarette smoke.
Journal of Chemical Education • Vol. 85 No. 2 February 2008 • www.JCE.DivCHED.org • © Division of Chemical Education
In the Laboratory
tive comparison between the solid particles in cigarette and narghile smoke. Almost no solid particles were observed in the narghile smoke; however, a black and smelly material called “tar” was detected in the smoke of one cigarette. The students try to dissolve the solids in water and in methanol and find that tar dissolves in methanol but is not water-soluble. The students connect the result of the water insolubility to their previous knowledge about intermolecular interactions and as result solubility properties. They discuss the results and realize that it is not easy to remove tar from the body after it has been deposited. The results of this station support the common belief that smoking narghile is not dangerous because no tar from the narghile smoke was collected on the filter. At the next station we will contradict this belief by checking a different component of the narghile smoke. Station 3: Vapor-Phase Substances in Smoke The topics we discuss at this station are gases in general and poisonous gases in particular. The students quantitatively measure three poisonous gases, NOx, SO2, and CO, and compare the quantity of each of the poisonous gases in cigarette and narghile smoke. Three different commercial tubes,2 one for each gas, were purchased to assess the quantity of gas in the smoke. The commercial tubes were connected to a “smoking apparatus” as shown in Figure 3. The chemical reactions that occur between the gases and the indicators inside the tubes are described in eqs 1–3.
5CO I2O5 3NO 2CrO3
H2SO4
H2SO4
I2 5CO2
(1)
3NO2 Cr2SO3
SO2 2NaOH
Station 4: Simulating the Effects of Smoking on Lungs Smoking is an interdisciplinary subject. At the last station, the students learn about the physiology of breathing. They observe diagrams of the respiratory system and fill “healthy pig”3 lungs with air using a mechanical pump. After understanding the physiology and the mechanism underlying healthy lungs, another pair of lungs is put on the table, “smoking pigs” lungs. The students fill the two pairs of lungs with air and compare them. After observing and touching the lungs (with gloves) they determine the differences between the two pair of lungs regarding color, volume, and flexibility and even find that carcinogenic growth exists in the “smoking pigs” lungs. Hazards All stations operate with well-ventilated fume hoods, and a glass shield separates the students from the smoking machines. All students wear safety goggles and during stations 2 and 4 they wear protective gloves. Methanol is toxic by inhalation, ingestion, or skin absorption. 1,3-Dihydroxypropane is harmful if swallowed, inhaled, or absorbed through the skin. Conclusion
2NO2 2(C6H5)2NH (C6H5)2NNO (C6H5)2NH:HNO3
(2a)
smoke had a higher content of CO than the cigarette smoke. With SO2, the difference between the cigarette and narghile smoke was dramatic: whereas no SO2 was found in the cigarette smoke, a high concentration of SO2 was detected in the narghile smoke. We assume that the high content of poisonous gases in the narghile smoke is caused by two factors: the tobacco quality and the coal that is used to operate the narghile. The results from this station demonstrate the dangers of smoking water pipes.
Na2SO3 H2O
(2b) (3)
There was no significant difference between the NOx concentration in the cigarette and narghile smoke. However, a significant difference between the concentrations of CO and SO2 in cigarette and narghile smoke were found. The narghile
The main purpose for developing this laboratory activity was to create an opportunity to link chemistry to a subject that is relevant to high school students. In addition to the effect on class enrollment, we found that these activities had a major influence on students’ attitudes towards smoking and their knowledge of the subject. In order to learn about the “anti-smoking” influence of this activity on high school students, we are conducting comprehensive educational research focusing on this important aspect of the activity. The results of this study will be published at a later date.
vacuum pump water aspirator cigarette or narghile
filter
indicator tubes for poisonous gas cigarette or narghile
H2O
water trap
Figure 2. A “smoking machine” used to collect the solid particles from cigarette and narghile smoke.
Figure 3. A “smoking apparatus” used to measure the poisonous gases in cigarette and narghile smoke.
© Division of Chemical Education • www.JCE.DivCHED.org • Vol. 85 No. 2 February 2008 • Journal of Chemical Education
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In the Laboratory
Notes 1. According to the WHO (the World Health Organization) survey water pipe (narghile) smoking has recently become a popular phenomenon among Israeli adolescents (10). In the United States, national data are not currently available, and questions regarding smoking water pipes are not included in national surveys of health risk behavior. 2. Tubes used for detecting poisonous gases were purchased from Kitagawa: SO2 (No.103SE), NOx (No. 175SA), and CO (No. 1061). 3. The healthy and the smoking lungs are a commercially available kit. These lungs demonstrate the effects of prolonged smoking. The kit was purchased at eNasco. http://www.enasco.com/ (accessed Oct 2007).
4. Zimmerman, M.; McGeachie, J. Atherosclerosis 1987, 63, 33– 41. 5. Asmussen, I.; Kjeldsen, K. Circ. Res. 1975, 36, 579–589. 6. Lin, S. J.; Hong, C. Y.; Chang, M. S.; Chiang, B. N.; Chien, S. Arterioscler. Thromb. 1992, 12, 1305–1312. 7. Bartecchi, C. E.; MacKenzie, T. D.; Schrier, R. W. N. Engl. J. Med. 1994, 330, 907–912. 8. Camilli, A. E.; Burrows, B.; Knudson, R. J.; Lyle, S. K.; Lebowitz, M. D. Am. Rev. Respir. Dis. 1987, 135, 794–799. 9. Pilkington, F. B. Nursing Science Quarterly 1997, 4, 156–157. 10. Knishkowy, B.; Amitai, Y. Pediatrics 2005, 116, 113–119.
Supporting JCE Online Material
http://www.jce.divched.org/Journal/Issues/2008/Feb/abs248.html
Literature Cited
Abstract and keywords
1. Zoller, U. J. Chem. Educ. 1979, 56, 518–519. 2. CDC Morbidity and Mortality Weekly Report. 2005, 54, 625–628; http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5425a1.htm (accessed Oct 2007). 3. Ross, R. N. Engl. J. Med. 1986, 314, 488–500.
Full text (PDF) Links to cited URLs and JCE articles
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Supplement Student handouts Notes for the instructors
Journal of Chemical Education • Vol. 85 No. 2 February 2008 • www.JCE.DivCHED.org • © Division of Chemical Education
