Student understanding of chemical equation balancing

Abstract Fourteen high school chemistry students from two different schools were interviewed in depth on how they balanced simple chemical equations, the knowledge they employed while balancing the equations, and their representation of the balanced equations with diagrams. The equations were of the type employed when students are first introduced to chemical equation balancing in high school. All students were able to successfully balance the four equations presented to them. However, seven of the twelve students were not able to construct diagrams that were reasonably consistent with the notation of the balanced equation. It was further noted that these same students possessed very poor understanding of the concept of chemical subscript and were willing to violate the balancing rule which states that subscripts are not to be changed while balancing equations. The five students who were able to make consistent diagrams also possessed good concepts of subscript and the balancing rule.