An Investigation of Chemical Identity Thinking

Chemical identity is a foundational crosscutting concept in chemistry and encompasses the knowledge, reasoning, and practices relevant for the classification and differentiation of substances. Substances are found everywhere – from the chemistry classroom to the kitchen at home – so classification and differentiation of substances is important for everyday decisions as well as challenges that are solved using chemistry. An understanding of chemical identity, then, is essential for scientifically literate citizens in addition to students training to be chemists. A better understanding of how chemical identity thinking develops could be used to inform instruction and education research, with the intent of producing students and citizens who can use their chemical knowledge to reason with in order to practice chemical identity thinking. This thesis characterizes chemical identity thinking from the perspective of chemical identity knowledge and chemical identity practices, both of which contribute to chemical identity thinking. First, the literature is examined for existing research on how students perceive substances and chemical identity, and a hypothetical learning progression for chemical identity thinking is proposed. This is followed by the design of a qualitative instrument, the CSI Survey, to capture the chemical identity practices exhibited by students at a range of education levels (8th grade – 4th year university). The data collected using the CSI Survey are analyzed using content analysis. Eight unique themes corresponding to chemical identity practices (the application of chemical identity knowledge and reasoning) are revealed by this analysis (change, class, composition and structure, function, organism effect, sensory information, source, tests and experimental values). The application of chemical identity knowledge in biochemical contexts by both expert biochemists and biochemistry students is investigated in the final chapter, and the chemical identity knowledge observed in the biochemical contexts is characterized using the eight themes of chemical identity practices. Suggestions are offered on how the products of the research on chemical identity thinking can be used to inform decisions in both instruction and research