Selecting big ideas, treating them as models
Traditionally in Chemistry students learn about the behavior of gasses through investigating gas laws. But a law is a description of a phenomenon and if taught through a “lens of laws” students focus their attention on correlations among variables. For example, as pressure increases volume decreases. Theories provide explanations for laws. Explaining gas laws requires a keen understanding of molecular movement and how energy influences this movement. One of the challenges is that many of the gases we interact with one a daily bases are not visible. For this unit of instruction Bethany chose to have students reason with a familiar gases first: air and steam. She posed a puzzling phenomenon about an oil tanker that collapsed after being steam cleaned and sealed. Students developed initial models about what could cause the tanker to collapse and then did experiments with pop cans crushing with the aid of steam to add to the initial models. The pop can experiments helped students link an observable phenomenon with theoretical components such as the role of phase changes and the speed of gas molecules but to reason with the role of pressure inside and outside of a system; students did additional experiments and read about pressure. Over time students constructed a rich explanation for the oil tanker collapsing, while also considering similar phenomena. Students were then ready to apply what they learned to less similar observable phenomena. Bethany chose a set of relevant phenomena to students’ lives and had students explain modifications made to race cars based on their understanding of the gas laws. Students could choose to think about modifications to tires or engines.
Focus on topic or “things” |
Focus on observable processes • Teacher selects as focus “what is changing” in a system or how conditions affect a naturally occurring event. |
Explanatory model focus |
