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TGSU2: Key features of students’ understanding (2) LINKS Particle theory In order to explain change of state and mixing, students are taught a ‘basic’ particle theory, which talks in general of the 'particles of a substance' without distinguishing between atoms, molecules and ions. Often, when students are introduced to these ideas, they are susceptible to two alternative models: Model A: Particles in the continuous substance. In this model, the particles are seen as being in the substance, like peas in water, rather than being the substance itself. This model is not helpful and may actually inhibit learning. Model B: Particles are the substance, but with macroscopic character. This model is more useful, as the particles are seen as the substance itself. However, they are seen as small bits of it, having the same qualities and properties as the substance. So, for example, salt particles would be thought to be hard and transparent. Whilst model B can help towards understanding some aspects of changes of state and mixing (dissolving), it prevents any meaningful understanding of atoms and chemical change. Without care, our teaching can inadvertently reinforce either of these alternative models. Developing an appropriate particle model, in which properties of state are seen as collective properties of the particles, is a challenging task. not applicable more info tgsu1: notes tgsu2: notes tgsu3: notes tgsu4: notes tgsu5: notes tgsu6: notes more info   < prev | next >

a Science Enhancement Programme CD-ROM 2005   user guide