Although it is important for students to learn to solve problems involving "the gas laws", the reason for including the study of gases in the curriculum goes far beyond this; the subject provides an ideal opportunity to illustrate, by example, how the creative use of some simple principles of mechanics can provide a surprisingly good description of the simplest state of matter. A major objective of these lessons is to help students to get a feeling for the kind of reasoning that goes into the development of the scientific model that we call the "ideal gas". Beginning students in Chemistry are notoriously hesitant to undertake the development of conceptual models of their own, preferring instead the relative comfort of learning the usual standard set problems. It is hoped that bringing the students into more intimate contact with the thinking behind the laws will build both interest and confidence.
The eleven lessons of this unit are mostly quite short, so that students can concentrate on just a few concepts at a time, and they can go through them in any sequence. Each ends with a summary screen and the display of a "score" which students are encouraged to use for self- assessment. The emphasis is very definitely on concepts rather than on learning "formulas" or the proper mathematical development of the kinetic molecular theory. The level is aimed at first-year college/university, which means that the lessons should for the most part be suitable for high school use as well. The fact that a number of the topics in the last two sections are normally considered "beyond the scope" of many introductory courses should not prejudice instructors against recommending them to their students; these topics are interesting and they introduce concepts that can be built upon later. At the other end of the scale, the lesson on atmospheric pressure and the barometer was developed in response to our experience that few of our incoming first-year university students are able to explain how a barometer works.
Throughout the lessons there is continual emphasis on predicting relationships and on in- terpreting graphical information. This is one area in which interactive CAI can probably do considerably more than can traditional methods of instruction. A good example is the discussion of the three-dimensional PVT surface in the fourth lesson, which is difficult to convey in lecture (students have enough difficulty taking notes in two dimensions!), and for some reason is considered too trivial (or intimidating?) for textbooks. The goal of all this goes considerably beyond teaching "facts" about the properties of gases; our hope is that these lessons can help students develop habits of questioning and analysis that will serve as useful tools in any quantitative subject.
This three-dimensional P-V-T surface is explored in Lesson 5.
The Properties of Gases lessons are organized into eleven sections as detailed below:
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