CO2 IN and OUT

Contextualize

The analysis of chemical reactions that produce carbon dioxide and release it into the atmosphere, and the exploration of chemical processes that could capture this greenhouse gas and transform it into useful products creates opportunities to introduce central concepts and ways of thinking in chemistry. For example, estimations of the carbon footprint of different products and processes can be made using simple stoichiometry calculations, and the thermodynamic feasibility of carbon capture strategies can be evaluated using procedures based on the second law of thermodynamics.

Focus

The following infographic depicts the systems in interaction analyzed during the lesson. CO2(g) is a product of chemical processes used in modern societies to generate energy, such as the combustion of fossil fuels for transportation. Due to the role of CO2(g) in global warming, there is great interest in devising strategies for capturing and sequestering this gas from the atmosphere, transforming it into useful products:

Define

Central Ideas:

Many activities in which humans engage and the generation of products we consume produce substances, such as CO2(g), that affect life in our planet.
The amounts of substances emitted by human activities can be calculated considering the nature and amounts of the substances consumed.
We can use chemical processes to capture harmful emissions and use the products for various purposes. To evaluate the feasibility of these processes, we need to analyze reaction directionality.
Reaction directionality is determined by the relative potential energy and number of configurations of reactants and products. These quantities can be inferred from changes in the enthalpy and entropy of the system due to the reaction.
The change in Gibbs free energy is always negative for any product-favored process at constant temperature and pressure.

Core Practices:

Use computational thinking to estimate amounts of products and changes in thermodynamic properties during chemical reactions.
Apply models to semi-qualitatively evaluate changes in the relative potential energy and number of configurations of reactants and products during a chemical reaction.
Analyze and interpret data to evaluate the benefits and costs of using different fuels and the thermodynamic feasibility of different chemical reactions.
Engage in arguments from evidence about the pros and cons of using different products.

Systems Thinking Skills

System Composition: Identify and characterize properties of reactants and products in chemical reactions involved in systems that produce or capture CO2.
System Behavior: Infer the CO2 emission coefficient of different processes and the directionality of potential carbon capture reactions.
System Effects: Identify and characterize differences in various fuels' environmental and economic impact.

Socio-environmental Competencies

Evaluate the environmental and economic benefits, costs, and risks of relying on different fuels to produce energy and of various processes for capturing CO2 emissions.

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 of CO2 emissions and capture in modern societies. The lesson is designed for an introductory general chemistry lecture course at the university level.

CO2 In and Out.pptx

This example lesson introduces and applies the following chemistry concepts: Basic stoichiometry calculations involving chemical reactions, enthalpy and entropy changes during chemical reactions, Gibbs free energy of reaction, and reaction directionality based on the 2nd law of Thermodynamics.
This example lesson assumes students already have a basic understanding of the particulate model of matter, the mol, molar mass, unit conversions, and matter and energy transformations during 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. As illustrated in the example lesson on CO2 emissions and capture, this can be accomplished by asking students to analyze relevant data that helps them identify the issues we seek to understand during the lesson. These activities 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 where students are asked to build a system map in which they brainstorm initial ideas about possible components of the chemical systems under analysis and their interactions:

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. For example, in the first part of the example lesson on CO2 emissions and capture, students explore how to use stoichiometric calculations to determine the CO2 emission coefficient of different types of fuels and use this information to decide which may be the best choice to reduce the carbon footprint:

In the second part of the lesson, students learn how to predict the relative potential energy of reactants and products, and thus the heat of reaction, based on the analysis of compositional and structural factors at the molecular level:

Zoom Out

Once students model and understand the phenomena of interest at proper 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 CO2 emissions and capture, students are asked to evaluate the thermodynamic feasibility of chemical processes based on the analysis of energetic and entropic factors determined by the composition and structure of reactants and products:

Connect

In the "Connect" phases of the lesson, students engage in activities that allow them to apply what they have learned to explore and analyze relevant systems and processes. For example, in the first part of the example lesson, they are asked to estimate their carbon footprint due to breathing:

While in the second part of the lesson they apply their knowledge to evaluate the thermodynamic feasibility of CO2 hydrogenation to capture the greenhouse gas:

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 as a "Let's Apply" (LA) activity focused on the evaluation of the process of dry reforming to capture CO2.

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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