One area explored in the second (in-depth) phase of the Learning in Science Project was "children's science," defined as views of the world and the meanings for words that children have and bring with them to science lessons. The investigation reported focuses on students' thinking regarding their views on particles and particle behavior. Students (N=41) were individually interviewed while they observed four events: a burning candle; the neutralization of an acid; the precipitation of lead chloride; and the explosive oxidation of magnesium. During the data gathering procedure (interview-about-events), students described what they saw happening and explained what happened. Selected student responses for each of these four events are presented and discussed. Among the findings reported are those indicating that a significant percentage of students: do not appreciate the basic particulate structure of all matter; are confused by the word "particle" with its multiple meanings, and do not understand the words "atom" or "molecule" in a scientific sense; do not consider that weight (or particles) are necessarily conserved in chemical reactions; and prefer to talk about what is observable rather than talking about abstract molecular models of what is happening. (Additional examples of children's use of everyday language, human-centered viewpoint and attribution of human characteristics to inanimate objects are provided in an appendix). (JN)