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Contextualize
Modern societies rely on diverse oxidation-reduction reactions to generate the energy that powers our vehicles. The amount of useful energy generated depends on the nature of the chemical process and the device's efficiency. These processes consume natural resources and produce chemical substances that can cause problems when released into the environment. This context creates rich opportunities to introduce central concepts and ideas in chemistry related to electron transfer during chemical reactions and help students identify critical factors to consider when evaluating the chemical products they use.
Focus
The following infographic depicts the systems in interaction analyzed during the lesson. Transportation in modern societies depends on technological devices that transform chemical energy into electrical and mechanical energy. These devices include internal combustion engines, electrical batteries, and fuel cells. The production and use of these technologies impact the economy and the environment in diverse ways.
Define
Central Ideas
Humans rely on exothermic chemical processes to generate energy used for multiple purposes, including transportation.
In many exothermic reactions, electrons in the system redistribute and adopt lower potential energy states. Tracking the redistribution of electrons is important to evaluate the amount of energy exchanged and control the process.
We can track the redistribution or transfer of electrons in a reaction by determining the “oxidation state” of the atoms involved.
When particles composed of atoms with different electronegativities interact, electrons may be redistributed or transferred in an oxidation-reduction (REDOX) reaction.
Combustions are exothermic redox processes in which we take advantage of the relatively high potential energy of electrons in the oxygen molecule to generate energy.
We can control electron transfer during a redox reaction in electrochemical cells to design more energy-efficient devices.
Core Practices
Predict and explain whether a chemical process is a redox reaction by analyzing electron redistribution between participating atoms.
Identify the major components in electrochemical systems and their interactions to model, predict, and explain their properties and behaviors.
Systems Thinking Skills
System Composition: Identify and characterize the properties of chemical substances and devices used for energy production in modern societies.
System Structure: Explore and identify interactions that lead to electron transfer between chemical species and mechanisms to control it.
System Behavior: Infer the behaviors that emerge in systems where electron transfer occurs between chemical species.
System Effects: Analyze the social, economic, and environmental effects of different approaches to harnessing chemical energy to satisfy our needs.
Socio-environmental Competencies
Evaluate the energetic benefits and costs of using different fuels in internal combustion engines attending to relevant factors.
Evaluate the benefits, costs, and risks of using different electrochemical devices as energy sources.
Evaluate the environmental, economic, and social impact of different energy sources used to power vehicles in modern societies.
Design
The following presentation includes a sequence of content and activities for a proposed two-week lesson (approximately six 50-minute sessions) that engages students in the development and application of chemical systems thinking to the understanding, analysis, and evaluation of energy sources used in transportation and their benefits, costs, and risks. The lesson is designed for an introductory general chemistry lecture course at the university level.
Energy Choices.pptxThis example lesson introduces and applies the following chemistry concepts: oxidation state, oxidation and reduction, redox reactions, electrochemical cells, cell potential, and energy output.
This example lesson assumes students already have a basic understanding of the particulate model of matter, molecular structure, electronegativity, and representation of chemical reactions.
The following diagram depicts a suggested schedule for the implementation of this example lesson:
The example lesson includes a set of interspersed activities (labeled "Let's Think") that students are expected to complete in small collaborative groups and then share their ideas in whole class discussions. These activities ask students to share and explore chemical concepts, actively engage in core science practices like analyzing data, making predictions, applying models, and generating explanations, and practice systems thinking skills. The specific system thinking skills that each activity may help foster are highlighted using representative icons. They also create opportunities for the instructor to formatively assess student learning and provide specific feedback to advance their understanding.
Map Out
During the "map out" phases of a lesson, students are introduced to the socioenvironmental problem under analysis to identify the systems in interaction. This phase should allow them to develop an overall view of the nature and complexity of the problem or phenomenon to be analyzed. Classroom activities in this phase of the lesson should create a need-to-know and opportunities for students to activate and share prior knowledge and experiences related to the phenomenon. For example, consider this activity in the introductory "map out" phase of the example lesson on energy choices where students are asked to identify specific technoscientific, economic, environmental, and social factors they would consider when comparing different energy sources to power vehicles:
Zoom In
During the "Zoom In" phases of a lesson, students engage in activities that help them identify the main components in the systems of interest, analyze their properties, and characterize their interactions at levels of granularity that are productive in making sense of the problem or phenomenon under consideration. In the example lesson on energy choices, students first explore how electron redistribution during chemical reactions may lead to energy transformation and transfer as illustrated by the following "Let's Think" activity:
In the second part of the lesson, students analyze how energy transformation and transfer during chemical reactions is controlled using electrochemical devices as illustrated below:
Zoom Out
Once students model and understand the phenomena of interest at submicroscopic levels of granularity, it is important to "zoom out" using activities that help them recognize system-level properties and behaviors that emerge from the interactions between components. For example, in the proposed lesson on energy choices, students are asked to apply their understanding about electron redistribution during redox processes to make predictions and justify energy transfer during combustion processes:
Students are also asked to apply their knowledge in the analysis of how the interactions and organization of system components result in emergent properties, such as the voltage and energy output in electrochemical cells as illustrated by the following activity in the lesson example:
Connect
In the "Connect" phases of the lesson, students engage in activities that ask them to compare the energetic, economic, environmental, and social benefits and costs of two types of fuels for use in internal combustion engines (ICEs):
As well as to apply their knowledge to analyze the socioenvironmental issues that the production of lithium-ion batteries generates:
Evaluate
The "Let's Think" activities interspersed in the example lesson create diverse opportunities to formatively assess student learning and provide specific feedback to advance their understanding to meet the lesson's learning objectives. These activities also help students evaluate strengths and areas needing improvement in their learning. As part of the summative assessment, we suggest implementing an activity that requires students to apply their understanding to analyze a different system of interest. This summative assessment could be completed individually or in small groups, inside or outside the classroom. An example of this type of summative assessment is included at the end of the example lesson on energy choices as a "Let's Apply" (LA) activity focused on the analysis of hydrogen fuel cells as alternative energy sources to power vehicles.
Reflect
During the implementation of the lesson, it is important to systematically gather information about student learning and performance that can help us critically reflect on aspects of the lesson that need to be modified to support student learning of the central ideas, core practices, and socio-environmental competencies targeted by the lesson.
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