In this study, we investigated young children's (ages 7-10) spontaneously c
onstructed or naive understanding of the particulate nature of matter prior
to any formal instruction in the domain. Fifteen students were interviewed
concerning their understanding of the macroscopic and microscopic properti
es of the states of matter (solid, liquid, and gas), as well as their macro
/microscopic understanding of phase changes and dissolving. Children expres
sed ideas about states of matter which were categorized as macrocontinuous,
macroparticulate, or microparticulate. Nine children (60%) stated beliefs
about matter which were macroparticulate in nature, and three (20%) express
ed microparticulate beliefs about matter. The three remaining children (20%
) held macrocontinuous beliefs about matter. Furthermore, a substantial num
ber of the children provided explanations of properties and processes which
were consistent with those beliefs. These children's beliefs about matter
were not fully and consistently developed across the spectrum of substances
from continuous solids to particulate solids to liquids to gases. We specu
late that children first develop local frameworks particular to different c
lasses of substances and then slowly expand these frameworks to include a w
ide range of substances and their properties, as well as such processes as
melting and freezing. (C) 1999 John Wiley & Sons, Inc.