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Learning and Teaching Strategies

From personal experience and research comes advice on what works and why

Roald Hoffmann, Saundra Y. McGuire

Six Teaching Tactics

2010-09MargHoffmannFB.jpgClick to Enlarge ImageMoving to the teacher’s side of the classroom, we recommend instructors grade on a contract with the students, whereby grades are based on a combination of a major, absolute performance component (examinations and quizzes) and a minor “curved” part of the course (such as labs and other multisection pieces). The only reason for curving should be fairness—if several graders are involved, for instance. The grading criteria—the percentage mastery equivalent to an A, B, etc.—must be explained to the students at the beginning of the course, along with a promise that the borderlines between grades will not be raised. Students are empowered when they see that the outcome of their course grade is dependent on their work, rather than on a comparison with the work of others. Young people react very positively to fairness; a contract boosts confidence.

However, the professor will need to construct exams such that the level of mastery of the material is accurately reflected by the grade that students achieve on the test. In psychometrics, this is referred to as content validity. In particular, one has to watch for misjudgments of mastery in multiple-choice exams of the type where the simplest arithmetic mistake will yield an incorrect answer.

The kind of contract we recommend is very scary to some department administrators, who may insist that each course has a predetermined median grade. Such worries, amusingly, reflect a lack of confidence in faculty members’ ability to assess mastery levels.

A second teaching strategy is to bring “real life” into the classroom. News, crises and everyday life open the mind. Devote five minutes of each class to a discussion of science in current affairs. Every minute spent this way is worth it.

Newspapers (print or online editions) sadly carry little science; what they do carry is often health-related. The stories rarely give chemical structures but sometimes name the molecules or drugs. But the structure of a molecule can be shown in class, along with a copy of the story.

From a stream of such short stories from the real world comes appreciation of the relevance of what is taught. In chemistry, students begin to see that small differences in the structures of molecules may determine whether a substance will hurt or heal, or both. For example, they may begin to understand that not all cholesterol is bad, or that the drug methamphetamine (crystal meth) and the decongestant it’s illegally made from in home laboratories differ by just one atom.

But the discussion of newsworthy topics may not be the most important part of this strategy. Ultimately, bringing real life into the classroom day in, day out builds a bond between teacher and student. Students begin to feel that the instructor has gone to the trouble of searching the media that very day and cares that students learn.

Here’s a strategy on which the two of us disagree: Allow each student to bring into a test or final examination an 8½-by-11-inch page on which anything in the world can be written.

One of us (Hoffmann) feels strongly that as we move from print to digital textbooks, and as it becomes increasingly more difficult to forbid a student to use a computer or fancy calculator in an exam situation, we are moving toward open-book exams anyway, like it or not.

The other co-author (McGuire) feels that this is not a good strategy because she has observed its negative consequences. In her experience, most students think that if they can bring in a “cheat sheet” to the test, they need not know anything because everything relevant can be written on the sheet, information of which they have no conceptual understanding. She feels that professors should provide information (such as constants) that students need, but are not expected to memorize. She stresses to students that they can only think critically using information safely stored in their minds—information that they own.

On the up side, the sheet serves as a security blanket for scared students. But its true purpose is to make the student review the material, to make judgments about what is essential and what isn’t, and to organize the material. The sheets can become a prime learning tool. With progress in the course, one of us has observed that students realize this, saying after an exam “I didn’t even look at the sheet.”

Getting students to think on their own is the primary objective of teaching, and care must be used to make students see multiple paths to an answer. Suppose a teacher in an introductory chemistry course has just gotten through discussing, say, the mass relationships in a combustion reaction: Octane (C8H18) is burned with unlimited oxygen to give water and carbon dioxide. He or she then continues: “Here we’ve seen how to figure out that if you burn 114 grams of octane with an unlimited amount of oxygen you will get 352 grams of carbon dioxide. But wait, the same ideas can be put to work in many more problems. For instance, I don’t have an unlimited amount of oxygen (the air intake on my car is clogged), I have 200 grams of O2. How much carbon dioxide would I get then from my 114 grams of octane? This is a so-called limiting reactant problem; seemingly different and tougher. Yet the same ideas are at work.

Here’s another problem: My Volvo travels 8,000 miles a year, at an average fuel consumption of 22 miles per gallon. How much CO2 am I putting into the atmosphere each year?”

Turning around the problem reinforces mastery of the underlying concept. There is nothing more convincing of a concept’s value than the feeling that it can be used for not just the problem that occasioned it, but for many other problems. And turning things around has an element of surprise to it. Repeating the same type of question in different permutations may seem repetitive to the teacher; we think it is rarely so to the student.

Surprise and humor can help bridge the gap between teachers and students. When one of us (McGuire) asked a group of Louisiana State University students to explain the difference between studying and learning, most replied that studying involves forcing yourself to memorize uninteresting stuff (as they put it), whereas learning means gaining insight into things you actually care about. How can we build into the travails of most study some of the psychological fun of learning—that tremendous empowering sensation of understanding after not understanding?

Judicious doses of humor help a lot. Few chemical stoichiometry problems or lists of the names of the foot bones could be imagined to evoke raucous laughter. But lapsing into a fragment of “Dry Bones” (the thighbone is connected to the hipbone…), or playing Tom Lehrer’s “Element Song,” or Blackalicious’ “Chemical Calisthenics,” or Diego Carrasco’s “Química” breaks tedium, giving the feeling of fun.

Humor is also a smile, or a surprise, or turning things around and looking from a different perspective. All of these things are part of what made the Marx brothers so good. Work in that direction, work to achieve surprise. Look in the course material for mistakes that lead to weird contradictions or unphysical results. These are the intellectual equivalent of pratfalls. Humorous situations, in moderation, are attention grabbing, emotionally satisfying and can create an environment that promotes long-term retention and learning. Humor also reduces stress, allowing students to enjoy the learning experience. Humor humanizes the instructor and builds a bond.

A final teaching strategy is to do still more demonstrations, even if you already do some. Although not every subject lends itself to doing demonstrations, chemistry certainly does. Mind you, demonstrations did not come easily to one of us, a theoretical chemist (Hoffmann). But he took to it and, in fact, learned how to turn white wine into red (and back again) from his coauthor. Demonstrations are somewhere between magic and science, somewhere between gripping theater and chemistry.

We know of no deeper silence in a classroom than during the first seconds of a demonstration. Theater directors and nervous concert-hall managers envy us those natural moments of rapt attention. The auditorium is hushed, awaiting change. The demonstrator does not fail to provide it, with color, flame, smoke or explosion. There ensues catharsis for the lecturer, a catering to all the senses of the audience, and, sometimes the only thing the students remember from a course.

Yet a demonstration is also a shifting of gears, from lecture to action. It is an intellectual alarm clock—“time to wake up, something is going to happen!” The act may be staged, but it is tangible. And it may invoke in the minds of a few students the essential question: “What is happening?”

A potential problem with this approach is that at times the link between demonstrations and what is being taught is weak. Moreover, a course overloaded with demonstrations could sacrifice learning for entertainment. But, perhaps in the lecture room it is as Daryle Singletary sings: “I ain’t never had too much fun.”








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