Experience indicates that many freshman science students have
distinguishing between observation and inference, mastering scientific
vocabulary, and working comfortably with symbolic representations.
They also confuse descriptions with causes, and fail to recognize the
interplay among facts, definitions, hypotheses, and predictions, which is
central to the enterprise of experimental science.
spite of these difficulties, many traditional presentations in chemistry
around in an unsystematic fashion among three domains:
the world of macroscopic observations, the underlying world of
atoms, and subatomic particles, and
symbolic representations used to represent substances and their chemical
behaviors. These presentations
often pay little or no attention to the intellectual struggle that led to
fundamental knowledge in chemistry, such as the relative atomic masses of
elements and the formulas of simple compounds.
Frequently they introduce students to atomic structure and electron
configurations early in the course, even though these aspects of the
are the most removed from direct experience and were elucidated after the
determination of relative atomic masses, chemical formulas, and molecular
geometry. Such approaches miss
opportunity to provide students with some historical perspective on the
discipline of chemistry, and a framework within which to develop formal
talk will describe some teaching
and topic developments used in a college freshman chemistry curriculum that
designed to help students connect observable phenomena with inferences and
hypotheses about the atomic world, and with the associated symbolic
representations. The presenter
been involved in curriculum development at the Massachusetts College of
and Health Sciences (MCPHS) for
past 16 years, primarily in a first-year chemistry sequence.
For the past 11 years, he has been drawing upon research in teaching
learning and performing his own in an effort to provide students with an
opportunity to develop reasoning skills, while working their way through the
freshman chemistry curriculum.
work is based on an action research methodology, which consists of planning
implementing specific classroom activities, observing and evaluating the
results, and then using conclusions to revise the activities and perform
cycle of the process. The
sources of feedback for evaluating this research continue to be observation
students as they engage in active learning, and evaluation of their
teaching techniques include the
of instructor-generated handouts to drive discussion-based classes, use of
think-aloud problem-solving sessions in various settings including the
classroom, extra help sessions, and the laboratory, and use of Socratic
questioning to guide students toward constructing concepts.
two-semester chemistry sequence at MCPHS is traditional in the sense that it
comprises a survey of a number of important topics.
However, topic development is based on introducing experimental
before concepts and theories, and some attempt is made to follow the
development of ideas. This talk
will focus on some topics presented in the first part of semester one.
In that semester, the behavior of various samples of matter is first
to help students create a library of terms including element, compound and
mixture. The presentation
making distinctions between chemical change and physical change, since this
often requires more knowledge about the atomic realm than students have at
point. Evidence suggesting that
matter is composed of tiny particles is presented.
Gravitational mass is introduced first as a measure of the attraction
the earth for objects, and then as a way to infer that denser objects
more matter. Making
hypotheses about observations associated with heating a metal in air
students to recognize the importance of making mass measurements. Conservation of mass is used to infer conservation of
laws of definite and multiple proportions are “discovered” by interpreting
the results of chemical analysis data.
about pressure and temperature measurement precede discussion of the gas
laws. Avogadro’s law is avoided at this point, since there is
simple experimental evidence for it.
work with the competing hypotheses of early 19th century scientists -
rule of simplicity and Avogadro’s hypothesis - to deduce possible relative
atomic masses of atoms and formulas of compounds. Students learn how Avogadro’s hypothesis eventually
won out, and this leads to Cannizzaro’s method of determining formulas and
relative atomic masses. By
eliminating topics like atomic structure, which are typically found in the
part of the chemistry curriculum, the student’s attention is focused on what
could be determined based on the limited evidence available at that time in
history. At this point in the
course, students do not even have access to a periodic table.
first-year chemistry students to develop a useful framework for organizing
knowledge has been a primary objective of curriculum development at MCPHS
goes back to the earliest work in the mid-1980’s.
The final part of this
will describe how progress in providing opportunities for students to become
better formal reasoners has led to a fundamental resequencing of topics in
first-year chemistry curriculum.
the restructured sequence, atomic structure is not introduced until the end
the first semester, and the beginning of the second.
Since active participation encourages reflection, part of the presentation will invite conference participants to try some of the activities that are used in this curriculum.