CHEMISTRY CHAPTER ZERO

Is Chemistry arcane?

In the mid-1980’s I taught a series of courses for secondary school teachers seeking to become teachers for the Texas 9 th grade science course, then called Physical Science. The idea was to retrain teachers in fields that were in low demand to teach in science fields for which the local school districts were chronically short of teachers. The teacher described in the following anecdote had taught Home Economics for several years.

These teachers were not able to use algebra as a reliable tool. The course text was Conceptual Chemistry by John Suchocki, and the following homework problem, within the limits of my memory, comes from that book.

“A piece of dirty copper wire is inserted into the flame of a Bunsen burner, where it becomes bright pink-orange (like a new penny). The wire is removed from the flame and allowed to cool, and as it cools it becomes black. Does the cooled wire weigh more or less than the pink-orange wire in the flame?”

The teacher came to my office before class to ask for help with the problem – she had worked on it the previous evening and was confused and frustrated. I asked her leading questions, and she readily told me that the flame cleaned the surface of the copper wire and that once the wire was removed from the flame, oxygen reacted with the copper atoms on the surface to add oxygen atoms to the surface. But... she could not tell me whether the cooled wire weighed more than the heated wire. Indeed, she changed her answer each time I asked her a probing question. Clearly, she was just guessing.

I decided to call on her Home Economics background.

“Jane [not her real name], suppose that you go to the supermarket and fill your basket with oranges [I thought these would be as close to the color of clean copper as I could get], and then you add a layer of avocados [I needed something dark] on top of the oranges. Does your basket weigh more with the avocados added than it did before?”

“Oh, Dr. Melton, of course it weighs more.”

“Now, what about the copper wire?”

More guessing.

Clearly, Jane could reason about weights. In the familiar world, she could not get the problem wrong. However, as I thought about this conversation, I came to believe that she TURNED OFF her reasoning skills when asked to think about atoms. The atomic world was ARCANE, not governed by our common reasoning, and one simply had to guess. Or if the teacher has told the student what material will be on the exam, the answer is something to be remembered [for a while] but not reasoned.

This is just one instance, and it may not provide a general truth. However, it drives my teaching, and it drives the construction of this web site.

BIG IDEA :

If I can help teachers and students accept that atoms are real, even though they cannot see them with their eyes, then they can use their reasoning powers – at the middle school level – to construct molecules and understand the fundamentals of chemistry