4 THE PHYSICAL SETTING
4D) STRUCTURE OF MATTER
Nature of matter. Elementary- and middle-school students may think everything that exists is matter, including heat, light, and electricity (Stavy, 1991; Lee et al., 1993). Alternatively, they may believe that matter does not include liquids and gases or that they are weightless materials (Stavy, 1991; Mas, Perez, & Harris, 1987). With specially designed instruction, some middle-school students can learn the scientific notion of matter (Lee et al., 1993).
Middle-school and high-school students are deeply committed to a theory of continuous matter (Nussbaum, 1985b). Although some students may think that substances can be divided up into small particles, they do not recognize the particles as building blocks, but as formed of basically continuous substances under certain conditions (Pfundt, 1981).
Students at the end of elementary school and beginning of middle school may be at different points in their conceptualization of a "theory" of matter (Carey, 1991; Smith et al., 1985; Smith, Snir, & Grosslight, 1987). Although some 3rd graders may start seeing weight as a fundamental property of all matter, many students in 6th and 7th grade still appear to think of weight simply as "felt weight"--something whose weight they can't feel is considered to have no weight at all. Accordingly, some students believe that if one keeps dividing a piece of styrofoam, one would soon obtain a piece that weighed nothing (Carey, 1991).
Conservation of matter. Students cannot understand conservation of matter and weight if they do not understand what matter is, or accept weight as an intrinsic property of matter, or distinguish between weight and density (Lee et al., 1993; Stavy, 1990). By 5th grade, many students can understand qualitatively that matter is conserved in transforming from solid to liquid. They also start to understand that matter is quantitatively conserved in transforming from solid to liquid and qualitatively in transforming from solid or liquid to gas--if the gas is visible (Stavy, 1990). For chemical reactions, especially those that evolve or absorb gas, weight conservation is more difficult for students to grasp (Stavy, 1990).
Particles. Students of all ages show a wide range of beliefs about the nature and behavior of particles. They lack an appreciation of the very small size of particles; attribute macroscopic properties to particles; believe there must be something in the space between particles; have difficulty in appreciating the intrinsic motion of particles in solids, liquids and gases; and have problems in conceptualizing forces between particles (Children's Learning in Science, 1987). Despite these difficulties, there is some evidence that carefully designed instruction carried out over a long period of time may help middle-school students develop correct ideas about particles (Lee et al., 1993).
Chemical changes. Middle- and high-school student thinking about chemical change tends to be dominated by the obvious features of the change (Driver, 1985). For example, some students think that when something is burned in a closed container, it will weigh more because they see the smoke that was produced. Further, many students do not view chemical changes as interactions. They do not understand that substances can be formed by the recombination of atoms in the original substances. Rather, they see chemical change as the result of a separate change in the original substance, or changes, each one separate, in several original substances. For example, some students see the smoke formed when wood burns as having been driven out of the wood by the flame (Andersson, 1990).
A clear picture has emerged of students' misunderstanding of the nature and behavior of matter. There is still a need, however, for detailed research on effective teaching strategies to correct this, especially to identify ways of leading students from a macroscopic to a microscopic understanding of matter. Although some likely precursors to a microscopic view have been suggested--for example, the notion of invisibly small constituents of substances (Millar, 1990)--they have not been formally evaluated.