This post is by Jacqueline Katz, the 2022-2023 Albert Einstein Distinguished Educator Fellow at the Library of Congress.
The concepts studied by scientists and science students can largely be classified as systems or system models. A system is generally a group of things or parts that work together, such as cells, molecules, forces, organisms. When attempting to understand the interworking components of a system, scientists often use system models. An example of a system model can be seen in the work of Dr. Joseph Priestley, a chemist of the late 1700s who explored the composition of air.
Show students the image of Priestley’s system model at the start of a unit on gases or metabolism and ask them what they observe. (They may record their observations on the Primary Source Analysis Tool.) Students will likely point out the mice, plants, and water bath. After initial observations, ask students if they would classify this as a system or a system model. When students respond, ask them what evidence they have; ideally, they will reference the components that are working together. Once students conclude that this is a system model, ask them what questions Dr. Priestley might have been trying to answer with it.
Students can then find support for or against their predictions using Priestley’s book, Experiments and observations on different kinds of air (1774). Provide students with excerpts from several experiments described in the book to help them understand how the system was used. They may work in groups to read about several of Priestley’s experiments, using the image to identify the components of the system model that Priestley used. Here are a few possible examples:
Throughout the book, Priestley outlines many experiments that he conducted using the pictured system model, so select additional experiments based on the content focus of your classroom.
Groups can summarize their experiment for the class and the class can develop a list of conclusions that Priestley likely made from his results. Depending on the class, these conclusions could lead into a discussion of the inputs and outputs of metabolic processes or the properties of gasses that explain the observations Priestley made.
If time allows, show students Benjamin Franklin’s response to Priestley’s findings. Franklin emphasizes a need to preserve trees because “there is nothing unhealthy in the air of woods.” The letter highlights the collaboration that occurs among scientists, as well as the applicability of a system model to an actual system. This primary source provides a platform for discussing the common scientific concept of systems, discipline specific content, as well as scientific practices. You can use other primary source system models to have similar 3-dimensional conversations, including these system models Ben Franklin used to study electricity.
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