Teachers TryScience

Note on Instructional Sequence

This lesson should be followed by You Are What You Drink (Part 2). In Part 2, students use the work they’ve done in Part 1 to actually design, test, and refine water filters. Part 2 also builds on students understanding about how changes in biodiversity affect ecosystem services.

The rubric associated with Part 2 includes assessment criteria for both You Are What You Drink lessons and can be used to assess how students apply their learning in Part 1 to the filter design and testing in Part 2.

Additionally, prior lessons about biodiversity and ecosystem services could strengthen the lesson sequence.

Note that this lesson assumes reasonable facility with developing and using models, and the CCC system and system models- if students are not familiar with these dimensions, more guidance will need to be provided.

Investigation 1: How does deforestation impact access to clean drinking water?

Materials

1 Glass with dirty water (water mixed with dirt or other substrate)

1 Water filter

Copies of readings (1 for each student)

Instructional Sequence

Brainstorm

First, ask students what are things that all people, regardless of where they live, need to survive. Record student answers on the board. Answers might include food, water, and shelter. Use student responses to begin to focus in on the topic of water.

Ask students to think about how much water they have had today- where did it come from? What did it look like? Give students some time to think about this before asking them to share out. Students may share answers that include the tap, drinking fountains, and water bottles. When describing what the water looked like, they may use words like “clear”, “nothing”, “clean”.

Ask students to think about the water that comes out of their taps at home. Ask them to do an individual quick write using the following prompt “Where does clean drinking water come from and what do you have to do to access clean water at home?”

Use this quick write to assess students’ prior knowledge about water systems and to identify their cultural values related to drinking water. If there are students who have experienced water insecurity, encourage them to share their experiences (if they are comfortable with this). Give students the flexibility to record their ideas in multiple ways (e.g., diagrams, written words, concept maps, storyboards).

Transition student thinking with a short class demonstration. Hold up a glass of dirty water and ask the class to describe what they see. You can also provide students with time to ask their own questions about the dirty water sample. Ask students if they would drink this water- why or why not? Use this opportunity to get students thinking about the importance of clean water, and what their lives (or lives of those they know) might be like without access to clean water, to anchor student interest in the topic. Be sure that the discussion is respectful of students who may have personal experiences with water insecurity. Use this discussion to emphasize a wide variety of clean water problems that people may face, including locally, to give all students an opportunity to engage with the issue (e.g., some students may think that clean water is something that can be taken for granted in the United States, or is only a problem in specific other countries- use examples of water purity problems in US cities, rural areas, etc.). You may want to give students the opportunity to find information about the consequences of unclean water by asking them to find articles or videos about the issue, or highlighting some of these stories or videos yourself for the whole class.

When students have had the opportunity to think about the effects of not having access to clean water, ask them to think about why clean water doesn’t exist everywhere. Ask students to consider the glass of dirty water- what might cause water to look like this? Ask students to provide evidence and/or reasoning when they share their ideas to assess current student thinking on this idea, and to identify misconceptions. Record some student responses, especially those that have to do with natural or large-scale contributors to water purity. Try to encourage students to think about the bigger picture, to set the stage for discussions of biodiversity and ecosystem services. Ask students what questions they still have- what do they want to know?

Provide students with a scenario that links ecosystem services to water purity, using images, graphs, charts, videos, etc. The scenario should include the following elements:

• A (local) community is suffering from a steady increase in water impurities.
• Features of the surrounding environment (include different factors that could impact water purity, such as deforestation);
• Time frames/scaling information for both the features and the water impurity

(Note: This can be expanded into a full analyzing and interpreting data activity by providing students with this data, asking them to analyze it, and then using the patterns/relationships they find in the data during the next part of the activity. This can also just be used as more of a qualitative frame for the next part of the lesson).

Ask students about their initial thoughts- based on what they know of this system, what could be causing the increasing water impurity? What questions do they still have? Have students record their thinking. Tell students they will have the opportunity to find information to help them answer questions about what kinds of pollutants are found in water and some potential causes of water impurities in this community, so that they can devise ways to help solve this problem.

Reading

Provide students with several readings about common sources and types of water pollutants. This should include readings that illustrate the connection between changes in biodiversity and changes in ecosystem services. Use the sample readings below to guide you. There is a reading about deforestation that articulates how changes in tree density and biodiversity affect our water system by leading to an increase in erosion as well as a decrease in an ecosystem’s natural filtration abilities. Similarly, a reading about oysters shows how changes in oyster populations also affect an ecosystem’s natural filtration abilities.

Ask students to work first individually to identify and record not only the types of pollutants but also details about the pollutants and their origins that may help them address the increasing water impurity in this community. Based on the information provided in the scenario of the community and what they gather from the readings, ask students to develop a model of the system based on evidence to describe what factors (natural or manmade) in the environment are contributing to water impurity in this community.

Encourage them to think about the following as they are reading:

• Are some pollutants more harmful than others? Support your answer with evidence from the texts.
• What are some filtration challenges associated with different types of pollutants?
• Are certain pollutants found in specific parts of the world?
• What are different sources of pollution?
• What characteristics of a pollutant affect its ability to be filtered?
• How could a decrease in the amount of trees in your local areas potentially affect your drinking water quality?
• How do changes in one part of an ecosystem affect other parts of the system? Provide specific examples.

(Note: This can be assigned as homework.)

Sample Readings

Types of Pollution

http://water.epa.gov/learn/resources/bigpollutants.cfm

http://water.epa.gov/learn/kids/drinkingwater/watertreatmentplant_index.cfm

http://water.epa.gov/drink/contaminants/

http://thewaterproject.org/US%20Water%20Pollution%20Basics.pdf

http://water.org/country/haiti/

http://www.americanforests.org/why-it-matters/why-it-matters-clean-air-and-water/

http://dnr.maryland.gov/forests/programapps/treesforsheds.html (Check the website of your own local governmental agency dedicated to environmental resource management)

http://www.cbf.org/about-the-bay/more-than-just-the-bay/creatures-of-the-chesapeake/eastern-oyster

(Note: you may also want to consider other forms of information, such as graphics, videos, graphs, charts, etc., for students who may struggle with the reading)

You can allow students to use their own format for recording information that will help them create their model, or ask them to generate a table or list based on a template you create. Inform students that they will use the data they’ve recorded to look for patterns or relationships and encourage them to select formats that will help them identify such relationships.

Sample Table

Be aware of scientific language in the readings students may have difficulty with- try not to define them before students have experienced them, and be prepared to help them understand the words in context without placing too much emphasis on vocabulary that doesn’t have a strong conceptual basis at this point in student learning progressions.

After students have had an opportunity to construct their models individually, ask students to share their models in small groups, with the goal of creating one group model. Remind students to be respectful in sharing their ideas and critiquing their peers ideas, using evidence and reasoning to support and refute claims that are made in the group. As you walk around, make sure students are coming to the conclusion that deforestation (and other ecosystem factors, if appropriate) is a driving factor of water impurity in this community, and that they are providing grade-level appropriate evidence and reasoning for this mechanism, which should include discussions of erosion and biodiversity, and ecosystem services.

Bring the class together as a whole, and ask them to share their ideas. If there are many ideas about contributing factors other than deforestation, that’s okay- focus on evidence and reasoning, and guide the conversation toward defining a specific problem that we can address and help solve: deforestation and the rise in water impurity. Ask students to think about what possible solutions we can suggest. Some popular ideas will likely be ways to mitigate deforestation, such as planting trees. You could create an extension activity for students to communicate these types of solutions, including possible benefits and costs, and pitch it to the local community, to engage interested students. For the rest of this lesson, tell the students that it’s a great idea, but ask them to consider the timescale- guide them to realize that deforestation intervention is a solution that will happen on a relatively long time-scale (encourage them to think of the ages of the people in the community, and when this would start affecting them)- are there any shorter term solutions we could help suggest? Use this to guide the conversation to water filtration.

Bring out the glass of dirty water again. Ask students to think on the scale of their own homes: ask students what they would do if the water that came from the taps in their homes looked like the sample in your hands and engage in a brief class discussion about some possible actions students would take. You can use student responses to transition to the topic of water filtration.

Now, pour the dirty water through a filter. Hold up the water again, and ask students if the filter “worked”. How do they know?

Ask students to create an individual annotated drawing that shows how they think a water filter works. You can use this to assess students’ prior knowledge.

Then, lead students in a class discussion using the following questions as examples:

• What are different types of water filters?
• How do they work?
• Why might water need to be filtered?
• What types of pollutants do filters target?

(Note: These questions are meant to assess student thinking and prior knowledge, and to address any misconceptions, or unclear understandings, during instruction. You can add additional questions based on student responses.)

Use student responses to the question “What types of pollutants are the filters filtering out of the water?” to encourage students to think about the information they gathered from reading and other forms of media earlier- what kinds of pollutants would we expect to see in the water in this community? What are the types and features of those pollutants? Use this discussion to transition into the next part of the lesson, giving students an opportunity to revisit the readings if necessary.

Investigation 2: Defining Criteria for Water Filters

After students have had time to share information about pollutants in small groups, ask the groups to share out information about types and features of pollutants they gathered from the readings, and record the information on the board. Ask students to look at the recorded information and note any commonalities or patterns to see if they can group like information- are there certain types or features of pollutants that may be particularly relevant for this community?

Next, ask students how the information they noted could affect the design of a water filter. Record their responses on the board. Working in small groups, ask students to determine pieces of information that must be taken into account in order to design a filter for this community, and which factors are not essential.

Ask the question, “What are some ways we can tell if a water filter is working?”. Ask students to first do an individual quick write to record at least two criteria, or expected/desired features of the design, that they think need to be met by a water filter. Use this quick write as a formative assessment tool to identify student thinking, and to identify areas of weakness regarding the concept of criteria.

Tell students that they will now generate criteria statements. Remind students that they are designing for a community in which there has recently been a great deal of deforestation. Guide students to use their models, readings, and research they did in Investigation 1 to think about how changes in the biodiversity of trees in the area cause changes in water quality for human residents of that area, and how this might contribute to the prevalence of certain contaminants. What types of contaminants would they expect to find? Why? Ask students to use their models and research to identify cause and effect relationships as support for their ideas. Turbidity is connected to a loss of tree coverage, but students might also ask clarifying questions about what caused the decrease in trees and the pollutants that might be associated with this cause. You can provide additional readings or time to research as needed.

Instruct students to work in small groups to create a criteria statement that includes at least two criteria for a water filter for the deforested community. For example, “A successful water filter must be able to filter out materials of 150 microns and larger and must filter 100 mL of water within 1 minute.” Ask students to use evidence and reasoning, from their previous experiences as well as their models, readings, and other provided materials, to justify why these are the criteria for the design. It may be helpful to ask students to each create a list of 5-6 features they would like to see, and then have them choose the essentials as a group, to foster a deeper understanding of criteria through argumentation about what would be absolutely necessary for a successful design, from their perspective.

Finally, have each group present their criteria statements. There may be some debate about what factors are included in the criteria, so if possible, allow groups to revise their statements after presenting.

As an accommodation for students who may be new to this type of classroom discussion, you can pair groups for peer feedback prior to whole class presentations.

Investigation 3: Defining Constraints and Articulating the Problem

Materials Per Group of 3-4 Students

3 types of filters (Brita, sand/rocks, etc.)

3 Samples of dirty water (water mixed with dirt, oil, food coloring, etc.)

Extra containers (cups, beakers, etc.) for catching filtered water

Stopwatch

Graduated cylinder

Materials Per Student

Copies of readings

As a class, review the final criteria statements. Ask students to list factors that would prevent people in the deforested community from using a filter that meets these criteria. Possible responses could include the time to build the filter, cost, or portability of a filter. Record student responses on the board.

Have students break into small groups. Provide each group with three samples of dirty water and three different filters. In addition, provide them with the stopwatch and graduated cylinder.

As an alternative for students who may need more structure, create stations that each group rotates through. You can also create worksheets or graphic organizers to help students record their observations.

For high interest students, this is a good opportunity to extend the lesson into an investigation of aquifers and natural filtration.

Instruct students to use the materials to gather data about the similarities and differences in filters. Each student should record the data and their data collection process in their individual science notebook. Ask them to look for patterns in their data that can be used to inform the design of a new filter. If needed, prompt students with ideas about how they could use the items to collect data. For example, students could use the graduated cylinder to measure the final output from each filter. You may also want to provide certain information about the filters, like cost, time to build, availability, resources used, and any side effects of using it.

After students have had time to collect data, come back as a class, and ask each group to share some of their findings, including which filter they would choose to use, and which one would be their last choice. Ask them to describe what it was about their least favorite filter that made it less ideal. Based on this investigation, ask students if they have any other items to add to the list that they started on the board (factors that would prevent the use of a filter).

Instruct students to do some additional research about factors that could limit the use of different types of water filters. You can use the sample readings or instruct students to do their own research, but make sure that their readings or other media sources present them with options for scientific knowledge about what influences constraints.

Sample Readings

http://environment.nationalgeographic.com/environment/green-guide/buying-guides/water-filter/shopping-tips/

http://www.rei.com/learn/expert-advice/water-treatment-backcountry.html

http://thewaterproject.org/biosand_water_filtration

http://www.nytimes.com/2011/09/27/health/27sari.html?_r=0

http://www.buylifestraw.com/the-cause

http://www.epa.gov/ogwdw/faq/pdfs/fs_healthseries_filtration.pdf

Guiding Questions

• What tradeoffs are presented in the readings?
• What would you look for in a water filter? How would your needs be similar or different to someone living in a rural part of India?
• What’s the ideal size for a water filter? Why?

Once again, ask students to use the research they’ve just done to add to the list of possible factors that could limit or prevent filter use. Tell students that using their research and the data they collected, they have generated a list of possible constraints. Then provide further information about the target community members that they can use to make inferences about which constraints would be most salient to them. This can include vocation information (are most of the people farmers? Office workers?), income information, and/or information about relevant values.

Based on their findings and reasoning throughout this task, ask students to identify the non-negotiable constraints- those that will most hinder the ability of the water filter to be constructed or implemented. Instruct students to work in small groups to combine the criteria they defined in investigation 2 with the constraints they have defined in investigation 3 to create a full water filter design problem statement to define the features of the design. For example: “A successful water filter must be able to filter out materials of 150 microns and must yield .75 liters for every 1 liter of water filtered within 2 minutes of filtration. There is only 1 hour to build this filter, it can’t weigh more than 3 pounds, and you must use only the materials provided.”

Finally, ask each group to share their problem statements.

Writing Task

As an assessment, ask students to create a written response to the following questions (this can be done as homework):

• How might the filter problem statement change if the community was experiencing a different ecosystem change? Indicate your reasoning in writing or in a diagram, concept map, or storyboard.
• Deforestation and water impurity effects on humans can be seen as the result of a series of interactions within a single system, or as a way two different systems can interact and influence each other, depending on how the system is defined, and the scale at which we are thinking. In this lesson, we have been thinking about the interactions within a single system- now consider them as pieces of two interacting systems.
  • Option 1: Create a model to describe a primary cause of deforestation. You may use prior knowledge, what we learned today, or additional research. In your model, make sure you represent the appropriate inputs, outputs, processes, and relationships that allow the factors involved in the cause to result in deforestation. Based on this model, are there other “side effects” in addition to deforestation? Describe how this may reveal a limitation of the previous model you created in the lesson. Be sure to include your evidence and reasoning, since there isn’t one “right answer”!
  • Option 2: Identify a populated area that is experiencing deforestation. Research the lives of the people in this area, and use your model of how deforestation causes water impurities to describe how deforestation may have a concrete impact on a person’s life in this area. Make a prediction about how the water filter solution will alter that impact, and what some limitations of this solution might be. Be sure to include your evidence and reasoning, since there isn’t one “right answer”!
  • Option 3: When we consider possible solutions to help the community experiencing rising water impurity due to deforestation, there may be other options. Describe one other solution, making sure you indicate on a model (either one you created in class, or an expanded model that includes other factors, like those that contribute to deforestation in the first place) at what point in the process leading to water impurities this solution would have an affect. What are one criterion and one constraint you might have for this solution? Be sure to include your evidence and reasoning, since there isn’t one “right answer”!