By Douglas Moran
Rethinking High School Curriculum: ChemistryUploaded: May 22, 2016
Q: For cleaning and disinfecting, what are the differences between soap, household ammonia, alcohol and chlorine bleach? Explain in terms of how they work.
I have asked this question of high school students who have recently completed a college-prep course in chemistry, and of adults with backgrounds in science. Excepting professional chemists. none could provide a competent answer beyond how bleach worked. When I graduated from high school, I could answer only two parts of this question.(foot#1)
This is an example of a large debate about various subject curriculum being badly outdated. Most of that debate revolves around what skills they need for jobs. But that misses a significant portion of the knowledge students need to acquire.
Continuing with Chemistry, my high school Chemistry classes were heavily oriented toward the knowledge and skills needed by someone who would work in a Chemistry lab. Virtually all of that was irrelevant shortly after I graduated. This was the late 1960s but from what I hear, some of the details have changed, but the problem is the same.(foot#2) New York State high schools at that time had a two track system. One was for college-bound students--their "Regents' Diploma" involved a curriculum promulgated by the State with a series of state-wide exams on that curriculum. The second track led to a "local diploma" that still required a broad range of courses, but that allowed alternative courses and variations. For example, that track's Chemistry course focused on chemistry that one encountered in everyday life: in the home, workplace, community ... My recollection is that the textbook was mediocre, but there were situations where the course could actually be both interesting and useful. The critical factor seemed to be having a teacher who was a non-young woman with a background in Chemistry, not an Education major who took a couple of dumbed-down Chemistry courses to become certified in that subject. Those teachers used their personal experiences to create a course by remembering where knowing the chemistry helped them in a situation or where others got into problems because they didn't know.
One area of everyday life where Chemistry plays a big role is cooking, and there are a variety of books on this. Foremost are the books by former Palo Alto resident (now of SF) Harold McGee, aka "The Curious Cook", including "On Food and Cooking: The Science and Lore of the Kitchen" (Amazon link) and "The Curious Cook: More Kitchen Science and Lore" (Amazon link). McGee and his books get cited in popular culture, for example an episode of the TV series "Bones".
Commenters: feel free to recommend other books on the science of cooking--I know that there are several dedicated to baking that provide a better treatment than the corresponding chapters in McGee's books. But that isn't the focus here.
One argument made for keeping chemistry lab work in the high school curriculum is that it teaches important skills--carefully following instructions for a specific task, precision of names (small differences in names can have dramatic/disastrous results), and adhering to basic, underlying safety rules. While these skills are part of various other subjects, the argument is that they don't have anywhere near the level of consequences--the student may learn how to do it, but not learn the importance of doing it. For example, in writing a computer program, failure to follow instructions or being imprecise in the names is easily fixed with a few edits. And failure to produce safe programs is routinely rewarded: shortcuts transfer cost to unsuspecting customers.
Another of the goals of laboratory exercises is to impress upon the student that reality is much more complex and messy than the impressions given by the textbooks and lectures. A simple example of this comes from a friend who had made fruit gelatin salad and garnished it with slices of kiwi fruit, and when she went to put it on the table found the slices floating in pools. Previously she had successfully made this dish, but that was using "vegetarian gelatin". However, conventional gelatin (Jello-type) is protein-based, and those proteins are broken down by the enzymes in the kiwi, and fresh pineapple ... Another (messy) exception: canned pineapple is OK--the canning process destroys the enzymes.
There are similar questions about the high school mathematics curriculum. For example, there are active discussions about replacing Calculus with categories of mathematics that are more likely to be used in Information Technology careers. My personal experience was that I never used Calculus outside that course and several required college courses (Physics, Signals Processing ...). Similarly questions are being raised about Algebra. Although I routinely did algebraic transformations throughout my career, some of the ones that my high school course spent significant time on were rarely used (for example, factoring polynomials).(foot#3) I chose not to use the Math Curriculum as the example here because there is already an extensive discussion on this, and (unfortunately) many of the participants assume, without evidence, that their own personal experience is typical.
The issue of updating the high school curriculum comes up frequently, and at some point it might actually happen. To understand why a change can be so difficult, you need to recognize the political and pedagogical issues. The fundamental political problem derives from inertia (social, not physics). The colleges have their expectations of what well-prepared students should know, and the testing companies market exams support those assumptions (for example, the SAT Achievement Tests). Consequently, for many students and parents, the course that best prepares the students for their future is not one that imparts knowledge that they will actually use but one that better prepares them for an exam that may determine which colleges they go to.
On the pedagogical side, you need to worry about having enough breadth and depth of what is covered--finding good example of enough of what needs to be covered can be difficult. Let me emphasize that: It is much harder than simply combining a set of facts into a lecture and declaring them "learned" because the students can remember enough of them on a subsequent test. Because the repetitions during the course may not be enough for long-term retention of the lessons, having the teaching examples correspond to everyday life has the decided advantage that there will be ongoing repetitions.(foot#4) However, the logistics can be problematic. There is the logistics of individual classes, and the logistics of scaling up a course offering so that it isn't dependent on particular individuals and related circumstances.
Another candidate for more course content is evaluating the science behind current events. Unfortunately, finding such topics that won't offend someone's politics can be difficult.
Caveat: One of the problems with updating a curriculum is that many of those involved can see only a small portion of the problem: Today's students are intimately aware of the course content and the short-term effectiveness of the teaching, but don't know what the future will bring (despite beliefs to the contrary). By the time they become parents of high school students, much of their experience will be obsolete. My experience with the education professionals is that they have such a different experiences, priorities and vocabulary that it is hard to understand each other's perspectives--just think about how different the workplace of a high school teacher or university professor is from most.
Note: My professional background is Information Technology, not Chemistry. But this blog is not about the details of a High School Chemistry curriculum, but of the general direction of one.
1. Informal, partial answer: Soap can be thought of as a molecule with one end that binds to oils and greases and the other end that binds to water. For soap to be effective, it needs to be pushed into good contact with the oils and then flushed with water to pull away the oil/grease that the soap molecules have grabbed onto. Sudsing--bubbles--helps with separating and carrying away the soap and what it has latched onto. The role of hot water is to soften up greases to make them easier to pull away.
Soap "disinfects" by removing the oils that were holding in place the germs...
"Detergents" operate in the same manner, and the use of this word can be ambiguous: Some include soaps as a subset of "detergent" and some use "detergent" for the non-soap substances that act in this manner.
Practical: If you mistakenly think of soap as dissolving oils rather than yanking them away, notice how this affects how you wash your hands. And how you understand the admonition to not overload a washing machine.
Household ammonia interacts with greases to form soaps that are then easily flushed away.
Chlorine bleach is a very aggressive oxidizer--it rips apart many other molecules. Warning: Don't mix chlorine bleach with ammonia (and similar chemicals): It is very dangerous.
Alcohol disinfects by disrupting various cellular functions, depending on the concentration used and the type: methanol ("wood"), ethanol, propanol ("isopropyl", "rubbing")...
"Extra credit": Other/alternative cleaning products such as vinegar and baking soda. "Extra credit": What works better in different cleaning situations, such as windows and greasy pans.
2. How times have changed: Could it be that HS Chemistry Lab is more relevant for those not intending to go to college? In the TV series "Breaking Bad", some of the early episodes revolved around using old-fashioned Chemistry Lab skills for superior manufacturing of Meth (methamphetamine). However, this series didn't produce an observed uptick in HS Chemistry class enrollments in areas with widespread Meth manufacturing. So much for the influence of TV.
3. When and where I was a student, Algebra was the watershed course between "math" as calculation (arithmetic) and math as representation, with algebraic transformation being the means to simplify (or clarify) the original representation into something that was practical to solve. Additionally it taught that there wasn't a simple mechanical recipe for solving a given problem, but rather a set of tools that you needed to choose between, with some of them turning out to not be helpful.
4. The problem of retention has long been recognized. My favorite studies are ones that repeat end-of-school-year exams at the beginning of the next year. These experiments find large losses, for example, students who got As on the test at the end of the course get a failing grade on the test administered after summer vacation. Part of this effect is due to what is being tested: When I was teaching, some of my test questions would be about things that a student who had done the homework would have had enough repetitions to remember at that moment. They weren't specific things that I expected the students to permanently remember, but rather proxies for a range of things the student should have learned by doing the homework.
An abbreviated index by topic and chronologically is available.
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