On the potential of live weighing as evidence of existence of gases

Abstract

The gas concept is fundamental for STEM learning, yet many hold misconceptions about gases, such as gases not having material nature nor being conserved in chemical reactions. Some suggest perceptual evidence of existence (such as colour or smell) is key to acknowledging the material nature and subsequently the role of gases in mass conservation. In this paper we did a preliminary exploration of whether a real-time scale with graphical interface can serve as evidence of existence of gases. To do so, we designed and conducted a teaching unit in which preservice primary science teachers (n=4) used a real-time scale to perceive weight change during two chemical reactions in which gases evolved or absorbed. The teaching unit was audiorecorded and observed. We found that two important design elements when introducing live scales were a) hypothesis line graphs to familiarize with the graphical interface and b) the choice of live (as contrast to logged) measurements to promote learners’ attention during observation. Learners displayed subtle signs of trust in and familiarity with the instrument, indicating a potential for the live scale as evidence of existence of gases.