When students begin to make the transition to accurately using simple molecular chemistry concepts, Level 2 begins, which is called the "Representing" level. At Level 2 of the matter progress variable, we see students using one-dimensional models of chemistry: A simple representation or a single defmition is used broadly to account for and interpret chemical phenomena. Students show little ability to combine ideas. Here students begin extending experience and logical reasoning to include accurate chemistry-specific domain knowledge. In the conceptual framework, this is when students begin to employ definitions, terms, and principles with which they later reason and negotiate meaning. At this level, students are concerned with learning the language and representations of the domain of chemistry and are introduced to the ontological categories and epistemological beliefs that fall within the domain of chemistry" students may focus on a single aspect of correct information in their explanations, but may not have developed more complete explanatory models to relate to the terms and language.