CLEAN Water

Contextualize

Ensuring access to clean and safe water is one of the most pressing grand challenges facing the world. The analysis of how different methods for purifying waste water or desalinating ocean water work and the evaluation of their benefits and costs creates diverse opportunities for introducing and applying fundamental concepts and ideas in chemistry, including properties of matter, phase behavior, and the particulate model of matter.

Focus

The following graphic depicts the systems in interaction analyzed during the lesson. Access to clean drinking water depends on technologies that eliminate unwanted chemical substances from seawater and wastewater. These strategies consume energy and have diverse impacts on the environment; one must evaluate these effects to make decisions about what is best to use in a particular context:

Define

Central Ideas

The survival of human societies depends on our ability to sustainably generate and use different resources, such as clean water.
Knowledge about the properties of substances, such as their phase behavior, allows us to separate them when present in a system such as ocean water.
Modeling a substance as a collection of identical submicroscopic particles in constant random motion and interaction helps explain and predict its physical properties and behaviors.
Substances exchange energy with their surroundings when undergoing a physical change. This exchange can be explained and predicted by analyzing changes in the kinetic and potential energy of their submicroscopic particles.
The sustainable production and use of different products, such as clean water, is facilitated by understanding their composition and behavior at submicroscopic levels.

Core Practices

Analyze data about the phase behavior of different substances to propose strategies to separate them when present in a mixture.
Use the particulate model of matter to explain and predict emerging physical properties and behaviors of substances in a system through the analysis of changes in the arrangement of and interactions between particles, as well as variations in their average kinetic and potential energies.

Systems Thinking Skills

System Composition: Identify physical properties of substances in a system that can be used as differentiating characteristics to separate them.
System Structure: Explore and characterize the interactions between particles in mixtures of diverse components.
System Behavior: Infer the phase behavior of a system based on the analysis of the interactions and organization of particles at submicroscopic levels.
System Effects: Analyze the impact of different variables on the selection of strategies to generate clean water.

Socio-environmental Competencies

Propose and justify strategies to separate the components of a system by thermal or mechanical methods, considering a variety of relevant factors, including scientific and technological considerations, but also environmental. economic, and socio-political factors.

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 clean water production methods. The lesson is designed for an introductory general chemistry lecture course at the university level.

Clean Water.pptx

This example lesson introduces and applies the following chemistry concepts: Phase transitions, particulate model of matter.
This example lesson assumes students already have a basic understanding of basic concepts in physics such as kinetic and potential energy.
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 clean water, this can be accomplished by engaging students in completing introductory readings describing the problem to be analyzed and using this information to complete an initial system map. These activities create a need to know and opportunities for students to activate and share prior knowledge and experiences related to the phenomenon:

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 clean water, students first explore the phase behavior of chemical substances at the macroscopic level, as illustrated by the following "Let's Think" activity:

While in the second part of the lesson students use interactive simulations of the particulate model of matter to explain phase transitions at the submicroscopic level:

Zoom Out

Once students model and understand the phenomena of interest at relevant 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 clean water, students are asked to apply their knowledge about the phase behavior of substances to devise strategies to separate mixtures:

Students are also asked to apply the particulate model of matter to explain how different methods of separation (e.g., filtration, osmosis, distillation) work:

Connect

In the "Connect" phases of the lesson, students engage in activities that allow them to explore the system-level effects of interactions between components in the system under analysis, as illustrated below:

As well as apply their knowledge in making decisions and suggesting or implementing individual or collective actions directed at addressing the societal and/or environmental problem under consideration:

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 sustainable methods for water desalination.

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.