Chemical Education Today
Physical Chemistry for Everyone I hated p. chem. class. I recall it was my least favorite course in the entire chemical engineering curriculum, and I had to take a year of it, plus a lab. I did not care for Schrodinger's wave equations, much less worrying about whether his cat was alive or dead. And I dreaded Hamiltonian operators: To date, I've never met an “operator” whom I liked. So it is strange now, indeed, to be a proponent of the idea that every citizen on this planet should learn some physical chemistry. It is not what you think, that misery loves company. (Although my experience with quantum mechanics dictates that camaraderie does improve one's suffering). Rather, it is because I am now charged with making the case for action on global climate change to policy makers and the general public, none of whom have the foggiest notion of the kinetic theory of gases. I'm recommending p. chem. because it is the course where you can learn about such things, including the greenhouse effect. But that is just it: the kinetic theory of gases is not really a theory at all. I suppose we call it a theory like the theory of gravitation by Sir Isaac Newton. But it is really a misnomer, because it is a fact that everyone should appreciate. The last time I checked, Newton's apple falls assuredly and precisely according to the law s = 1/2 gt2, each and every time. So it goes with absorption of infrared radiation by greenhouse gases. On some level, people think they understand the notion of the greenhouse effect because they've personally experienced a greenhouse or spent some time in a car warmed by the Sun. Yes, it is warmer inside the greenhouse than outside because of the surface of glass. But the average person on the street does not know why it is warmer inside the greenhouse: The Sun's shortwave radiation penetrates the glass and heats the plants and the soils inside, and the glass mostly prevents convective circulation and cooling. (They might believe the Sun's radiation is somehow magnified by the glass). In the earthly experiment we are conducting, there is a significant difference between Earth and an actual greenhouse. The infrared radiation from Earth's surface cannot penetrate as efficiently through the greenhouse gases into outer space, and that is what warms Earth's surface. Physical chemistry teaches us that every molecule with three or more atoms is capable of vibrating and rotating more violently when excited by infrared (back) radiation, and this motion traps heat in our atmosphere. Thus, carbon dioxide (CO2) is both a natural and an anthropogenic greenhouse gas, as are methane
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(CH4) and nitrous oxide (N2O). The kinetic theory of gases allows one to calculate ab initio the wavelength and the strength of such gases' greenhouse effect. Likewise, water vapor (H2O) is an extremely important greenhouse gas that is responsible for most of the “natural greenhouse effect”, which results in our planet having a comfortable average temperature of 288 K (15 °C) rather than a frigid 255 K (-18 °C). Warming the atmosphere with additional greenhouse gases induces greater evaporation of the seas and increases water vapor, which more than doubles the original effect. The crux of the educational problem is that people are busy with their everyday lives and are happy to dismiss a long-term problem, even one with such massive repercussions. They have become convinced by counterfeit information from skeptics that any warming we have experienced is natural and not a high priority for action. But they have sorely missed the point. Even if the current warming is natural, we are adding to it by emissions of greenhouse gases that are warming Earth still more. It is even more imperative to act now. Some of these gases remain in the atmosphere for more than 100 years. That is a fact, not a theory. My students in engineering must take 128 semester hours to earn the BS degree. Eighteen of those hours must be electives in the humanities and the social sciences. It is a great policy, one that helps them to be more balanced and educated citizens. Many choose to take more electives than required. They seem to enjoy the digression from mathematics and engineering and believe they are benefiting from it. So why are not the humanities and social science students required to take a similar number of hours in the natural sciences and engineering? I shudder to say that p. chem. could be one of them. Supposedly, there are three ways to change people's behavior: through education, by economic incentives, or via regulation and enforcement. The Journal of Chemical Education is about the first and the best way to change people's behavior... through education. Therefore, I say, “Physical chemistry for everyone.” (I've had mine already). Jerald L. Schnoor
Jerald L. Schnoor is a professor in the Department of Civil and Environmental Engineering, at the University of Iowa, Iowa City, IA 52242;
[email protected].
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r 2010 American Chemical Society and Division of Chemical Education, Inc. pubs.acs.org/jchemeduc Vol. 87 No. 4 April 2010 10.1021/ed8001368 Published on Web 03/09/2010
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Journal of Chemical Education
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