Current texts often have separate chapters for “Properties of Matter,” “Changes in Matter,” and “Atomic-Molecular Theory.” Atomic-molecular theory is often presented as a set of facts (declarative knowledge) about atoms and molecules, disconnected from any concrete everyday experiences that it may help explain. There is often no attempt made to acknowledge the counterintuitive nature of the claims or to show the usefulness of the theory. As a result, as research on student misconceptions makes abundantly clear, the majority of students fail to internalize the core assumptions of the theory, and they have little understanding of such important ideas as chemical change (see Driver et al., 1995, for reviews). As Schwab and others have argued, science is typically taught as “rhetoric conclusions” rather than as a complex process for making sense of the world (in the words of Niels Bohr, a way of “extending our experience and reducing it to order”) that rests on certain metaphysical and epistemological assumptions. Because of this, students do not appreciate what a tremendous intellectual construction a scientific theory really is, why it deserves great respect, and why it cannot be challenged by another idea that does not attempt to meet those epistemological standards. In an important sense, without constructing an understanding of those epistemological standards, students will not know the grounds on which they should believe important scientific theories.
In contrast, the proposed learning progression outlines a set of conceptual goals that can be investigated in a more sustained, mutually reinforcing manner, based on a principled interpretation of research on children’s interpretations of matter and materials. In particular, we note that the research enables one to identify phenomena and topics for discussion that will help students make progress with respect to each of the first three strands of scientific proficiency:
Understanding and using scientific explanations of the natural world. The learning progression develops atomic-molecular theory as a useful set of conceptual tools that resolve a wide variety of puzzles concerning properties of matter and changes in matter. Description at this level can explain conservation of matter and weight, the composition of materials (elements, compounds), the appearance and disappearance of specific materials, the constancy of materials across change of state, etc. These puzzles are real puzzles for children only if they already have a robust macroscopic understanding of matter and its measured properties. Furthermore, students must master several basic tenets of atomic-molecular theory and use them successfully before the power of atomic-molecular models is apparent.