Note on Instructional Sequence
In the previous lesson, students will have articulated criteria and constraints for designing a water filter. This lesson asks students to apply these criteria and constraints to design and evaluate a water filter.
This lesson assumes that students have had experience with developing models previously. If this is not the case, more scaffolding and guidance will be necessary.
Investigation 1: Revisiting the Problem
Review the criteria and constraints that students determined in You Are What You Drink Part 1. Tell students that they will now actually design and build water filters that address the problem statement they have articulated in You Are What You Drink Part 1. You can use the writing task from Part 1 as a pre-assessment of students’ readiness to engage in You Are What You Drink Part 2.
Students should have the criteria, constraints, and problem statement recorded in their science notebooks. As an added accommodation, you can post this information visibly in the classroom or lab so that students can continually return to this information.
Begin the lesson by first returning to the problem we are engineering a solution for: the deforestation of an area and the subsequent water pollution that has occurred. Ask students about the importance of biodiversity- why is it important? What are the effects of increased or diminished biodiversity in different ecosystems that they have examined? And what can we learn from natural systems that can help us with the design of a solution? Reintroduce oysters and their contributions to water filtration (which they may have briefly considered in Part 1) as another system in which they can examine these ideas. If students weren’t exposed to oyster filtration in one of the readings in Part 1, introduce this context now.
The importance of biodiversity and filtration for maintaining ecosystem services.
Use the scenario of oysters and filters inspired by oysters to not only help students learn about the connection between biodiversity and ecosystem services, but also to inspire student creativity when designing filters. Show a selection of the following videos and ask students to record information they find interesting or important in their science notebooks. You can provide the questions below to help guide note-taking.
Provide a graphic organizer to further guide note taking for struggling students.
Sample Videos
https://www.youtube.com/watch?v=VTuBbuUro4g#t=26
https://vimeo.com/100847263
https://www.youtube.com/watch?v=tOr2iz7WT-g
https://vimeo.com/124038511
https://www.youtube.com/watch?v=CcxaZm2NkCI
Note on Videos: If YouTube is blocked in your school, download the videos prior to class.
Questions to Guide Viewing
How have changes in the oyster population affected an ecosystem’s natural ability to filter water?
How can what you see in this example relate to the problem we are dealing with (deforestation and water purity)?
What information from the videos might be relevant to your water filter design? Why?
Thinking back to the previous set of lessons, what are some other natural filters that could inspire your design?
What instances of cause and effect relationships did you observe in the videos?
Developing a model of biodiversity and ecosystem maintenance impacts on water purity
Ask students to think about what they just learned about how oysters filter water, and to think back to the information about water impurities and deforestation they obtained in Part 1. Because students have already obtained information about these concepts, you can use this as an opportunity to 1) refresh student thinking, 2) assess whether students understand the connection between ecosystems and the design of a water filtration device, and 3) set students to think about their design in the context of the problem.
As students discuss the ideas they previously explored in Part 1, broaden the conversation to include biodiversity and ecosystem maintenance more generally, using the previous lesson as an anchor. As students discuss ideas about the importance of biodiversity, write ideas on the board. Encourage students to cite specific examples from their previous work on ecosystems. Ask students to consider why the ideas they are discussing are important to their task of designing a solution to the water pollution that results from ecosystem disruption. Ask students (individual or from groups) to share their ideas. Student ideas might include:
- We need to know how different parts of an ecosystem contribute to normal function and services
- We need to know what to expect if something changes- will we see big effects or small effects? How long will they last? These are important for our design
- We need to think about all of the parts that we are interested in for human use (e.g., water purity, food availability), and think about how biodiversity impacts human needs
- We need to think about the effects our solution will have on the system we are working with.
Note that you can guide the conversation to these questions based on student responses. Tell students these are all very important ideas, but they obviously are very complex and need to be examined carefully.
How can we do this in a way that will allow us to examine many questions, and for many different purposes? A model! Tell them that before they move on to designing and testing their solutions, they are going to use their model from Part 1, which describes why deforestation is associated with a local rise in water pollutants. They will build on that model to further flesh out the mechanisms by which deforestation can cause changes in water purity, updating their model as they go. They will then use this model throughout their design and testing phases, to think about relevant cause and effect relationships, and to make predictions about the impacts of their designs.
Ask students to reevaluate their models from the previous lesson. When evaluating, ask them to consider:
- What parts of the ecosystem need to be considered for this problem? What parts of the system are not important for this specific problem?
- How do these parts relate to each other? Think about cause and effect relationships between components.
- Based on those cause and effect relationships, what would you predict is going to happen to various parts of the ecosystem (including humans)?
- Where would your filter interfere with these predictions? How do those predictions change if you introduce your filter?
- Does this give you any further information about what might be important to consider when designing your filter? If so, you might need to update your criteria and constraints.
- What are the limitations of your model? How could this impact your thinking as you design a water filter?
When students have had some time to record their own thoughts and any updates or questions they have related to the model, ask them to share with a partner or small group of students nearby. They should update their models again as a result of conversation, if necessary.
Depending on where students are in their progressions for modeling, ecosystems, and cause and effect, you may want to explicitly write or announce these questions so that students can refer back to them, or you may want to use these as ‘look-fors’ as you walk around and listen to/look for student understanding. Remember to keep student misconceptions and misunderstandings in mind- encourage them to think through these ideas through their model by asking questions, and asking students to refer back to their models for answers- and remember to keep this process going throughout the lesson.
Give students an opportunity to obtain information they feel they still need for their models to help them design a solution.
When students have updated their models, updated any criteria or constraints they need to, and thought about how their water filter will work into the system within which the problem is contained, tell them they are going to begin designing, building, and testing their filters. Remind them to keep their models handy, as they will be using them to think about the impacts of their water filters.
Investigation 2: Designing and Building
Materials
Each student group will need access to the following materials (or similar materials):
- 0.5 liter (500 mL) plastic water or soda bottle
- ½ cup granulated activated carbon (GAC) (available from chemical supply stores or pet supply stores in the aquarium section)
- 2-3 cotton balls
- Jar (smaller in diameter than the 500 mL bottle so that the water bottle can be supported in the jar without falling through)
- Nylon stockings
- Styrofoam or other absorbent material
- 1 cup of sand
- Marbles or pebbles
- Kitchen knife or scissors (Use at your discretion. You can also ask students to bring any items they need cut to you.)
Each group will also need one dirty water sample made with a subset of the following:
- 3 tsp. of chocolate powder mix (used for making instant chocolate milk)
- Water (enough water for each bottle to be filled up 3-4 oz.)
- Pitcher or bucket for mixing powdered chocolate and water
- Something to represent pesticides such as food coloring
- Vegetable oil, to represent automobile waste
- Litter such as paper or plastic packaging
*The dirty water samples should relate to the types of impurities students might expect from deforestation-induced water impurities.
Classroom management note: You can limit students’ use of the materials as needed. Additionally, a few weeks prior to this lesson, you can ask students to bring in materials from home to help supplement this list.
Instructional Sequence
Split students into groups of 3-4. Present students with the various materials that they can use to build their filters as well as the dirty water samples they will be filtering. If possible, provide students with a cost estimate for the materials.
Ask students to examine the water filters and relate their observations back to the types of impurities they might expect from water that has been affected by deforestation. Encourage them to use evidence from the readings and research they did in Part 1.
Tell students that before designing a filter, they first need to think about a systematic way to test the filters. Tell students that each group will be testing their filter in front of the class, and each group is responsible for gathering information from the testing of every filter, not just their own. Having a clear testing protocol before designing is very important for engineers.
In their groups, instruct students to brainstorm a protocol for testing the filters and gathering data from these tests. Allow them to examine the materials more closely. Prompt students to think about how the criteria and constraints they articulated in Part 1 can help them evaluate the effectiveness of their filters. If necessary, you can begin brainstorming as a whole class to help guide students in the creation of the protocol. Also, prompt students to recall their criteria and constraints to help them consider different factors that should be included in the protocol.
Sample Protocol Items
- We will measure the amount of dirty water prior to testing, including appropriate and consistent units.
- Water will be poured from a height of 6 inches above the filter.
- We will use stopwatches to time how long it takes all of the water to flow through the filter.
- After 4 minutes have passed, we will again measure to see how much water has made it through the filter.
- We will rate the clarity of the filtered water on a scale of 1-5, and we will define what each number on the scale means, to be consistent.
After groups have had time to work, ask each group to share their protocol. As a class, use the different ideas to agree upon one shared protocol. There may be some debate as to what should be included. If needed, you can use student responses to determine the protocol yourself. At this point, you can ask students to create an organizer for collecting data, and ask them to think about what data they will need to get accurate and precise results. This will include information about the water, but also should include information about methods (e.g., number of trials, consistency in timing, etc.).
Next, instruct groups to begin brainstorming and sketching their designs in their science notebooks. Encourage students to refer to their models, which should reflect the videos, readings, and investigations they have completed so far. Ask students to think about cause and effect relationships and human needs that might influence their design. Tell students that they should annotate their designs with notes about how each feature of their filter- or features when used together- addresses some aspect of the criteria and constraints they have laid out. Allow students to examine and interact with the different materials, including the dirty water samples, to help inform their design. Ask students to make predictions about what the water will look like after going through the filter.
Students will have interacted with different types of commercial filters in You Are What You Drink Part 1. As an accommodation for students who may need help getting started, provide them with an actual filter and allow them to once again run a dirty water sample through the filter so they can observe how it functions.
Do not allow them to begin building until you have approved their design plan.
Approving the design plan will allow you to identify any issues that groups might run into as well as ensure that materials are not being wasted. A common problem that students might encounter is that their design does not actually allow water to flow through the filter into another container. Prompt students to think about how they might add holes or other openings to allow water to flow through and be captured.
For students with high interest, require groups to calculate the total cost of the materials used in their filter. This will allow students to determine the cost effectiveness of their filters during the testing phase.
Once you have approved a group’s design plan, they can begin building their water filters. Do not provide students with the dirty water samples yet. Again, you can monitor or limit the amount of material each student is using and depending on your students, you can even pre-cut some of the materials prior to the class.
Investigation 3: Testing
Materials:
- Brita filter or other household filter
- Stopwatches
- Graduated cylinders
- Other materials that students may have identified in their protocol
Instructional Sequence
You can now begin testing. One by one, provide groups with their dirty water samples. Each group should test individually while the rest of the class observes. During each test, students should use the protocol to gather data and record the information in their science notebooks. By the end of testing, the class should have a complete set of data about each filter.
In addition to the student designed filters, have one group also test a Brita or other household filter. You can use one of the same filters from You Are What You Drink Part 1. Encourage students to think about how the how household filter’s performance compared to the filters they designed.
As an added accommodation, you can create a worksheet or graphic organizer to help students record their data.
Investigation 4: Evaluating and Iterating
Materials
Each student group will need access to the following materials (or similar materials):
- 0.5 liter (500 mL) plastic water or soda bottle
- ½ cup granulated activated carbon (GAC) (available from chemical supply stores or pet supply stores in the aquarium section)
- 2-3 cotton balls
- Jar (smaller in diameter than the 500 mL bottle so that the water bottle can be supported in the jar without falling through)
- Nylon stockings
- Styrofoam or other absorbent material
- 1 cup of sand
- Marbles or pebbles
- Kitchen knife or scissors (Use at your discretion. You can also ask students to bring any items they need cut to you.)
- Copies of the rubric
Each group will also need one dirty water sample made with a subset of the following:
- 3 tsp. of chocolate powder mix (used for making instant chocolate milk)
- Water (enough water for each bottle to be filled up 3-4 oz.)
- Pitcher or bucket for mixing powdered chocolate and water
- Something to represent pesticides such as food coloring
- Vegetable oil, to represent automobile waste
- Litter such as paper or plastic packaging
Instructional Sequence
Briefly review the results of the testing. Ask students to do a quick write in their science notebooks or on a separate sheet of paper to respond to the following questions. Provide 1-2 minutes per question.
- Which filter features seemed to be most effective for the target community? Use evidence from the filters you observed to support your answer.
- If you had to pick one filter to buy now for use in the target community, including the Brita filter, which would you purchase? Use evidence from the filters you observed to support your answer.
- Which filter would work best in the context of the ecosystem we are working with? Use evidence from the filters you observed to support your answer.
- Which filter would have the least impact on the environment? Use evidence from testing to support your answer.
Prompt them to use the criteria and constraints and the evidence from testing to support their answers. Additionally, prompt students to consider the models they developed, including updating the models, and using the data they collected as well as their models to support their answers. Use these quick write responses to assess individual student thinking.
After students have had the time for individual reflections, engage in a group discussion to analyze the different components of the filters. Use this discussion to highlight the Crosscutting Concept of Cause and Effect by asking students to think about cause and effect relationships and how they may be used for prediction. Use the following questions to prompt students to use the data they have collected to discuss the effectiveness of each component individually as well as the ways the components worked together.
- Describe how your water filtration system performed. Can you identify which part of your device caused this? Was it many parts working together?
- In your tests, did you observe any patterns between certain features and certain effects? Discuss what further tests you would need to conduct to determine if the feature caused the effect, or if it was correlated with the effect?
- How did defining the criteria and constraints in Part 1 help you think about the best way to design or evaluate the solution?
Tell students that iteration, the process of repeating, is an important part of design and engineering. Engineers do not find an optimal solution immediately, but instead refine their designs over time. Ask students to think about their own experiences, both in this lesson as well as prior experiences- why is iteration important? What kind of information would be missing if they didn’t repeatedly test, modify, and retest designs?
Inform students that they will now redesign their water filters, using the data they collected during the test. Be clear that the protocol for testing the iterated design must be the same protocol that was used in Investigation #2. Take time to review this protocol if needed.
Iteration is a key piece of the engineering process. You should have students actually repeat portions of Investigations 1 and 2 to build and test a second version of their design. Testing the redesigned filter may reveal new information that can help build students understanding of the design process. For example, they may find that their original design was more effective or that even small changes can have a large impact on efficiency. If this isn’t possible, provide time for students to create annotated blueprints of the changes they would make based on the first round of testing.
At this time, you should also inform students that they will be presenting their iterated designs to a panel of “judges”. Tell them that the judges will be interested in knowing how their design addresses the problem posed throughout Part 1 and 2 of this lesson: water impurities resulting from deforestation. Tell students that in their presentations, they should:
- Describe the problem in the context of the ecosystem: what happened? And what are we worried about?
- What considerations did we need to take into account? These should be both scientific and engineering in nature (e.g., scientific information about ecosystem maintenance and biodiversity; materials and cost; human needs; environmental impacts). Students should use their models to show their thinking.
- Define the problem and the criteria and constraints they defined.
- How was the water filter designed to meet these criteria and constraints? This should include the design, as well as results from testing, and evaluation, and any redesigns.
Tell students they should also be ready to answer questions about the following, based on their designs and their models, including cause and effect relationships they have identified:
- How would your design address human needs?
- Do you think there could be any unintended consequences (positive or negative) from your design? How would you expect these to impact the rest of the system?
- Which features of your filtration system did you think were the most important? Why? (Include both the engineering and science perspectives here.)
- For specific effects you saw on the water, or might see in an ecosystem, what was the cause? Was there only one?
- What were the limitations of your designs, as well as the testing parameters here? How did those limitations factor into your thinking?
Note that you can give students these questions, additional questions, or a subset of these questions, depending on how far along they are in their learning progressions.
Review the rubric with students and allow them time to ask clarifying questions. After reviewing the rubric, allow students time to iterate.
Investigation 5: Presenting a solution
Materials
- Copies of rubric for each student
Preparation
If you’d like to have a panel of outside “judges” sit in for presentations, be sure to invite other teachers prior to class. Alternatively, the class can serve as judges for one another. As an added component, the judges could represent corporate investors or a town council that is interested in a filtration system for their town. Each judge could be a different type of stakeholder or represent a different point of view. If this is the case, make sure students think through what different stakeholders may be interested in, what questions they might ask, and how to address these differences. This might require additional conversation and supports.
Instructional Sequence
After students have had time to refine their designs, tell them that they will now be “selling” their designs to a panel of judges. Students should create a compelling argument that pulls evidence from the work they did in You Are What You Drink Parts 1 and 2. They will then present their argument in front of the panel. Again, review the rubric with students and allow them time to ask any new clarifying questions.
You can allow students to make this argument as you see fit- for example, presenting their models and designs, doing a demonstration, or participating in a question-and-answer forum. Having an interactive forum for students to engage in argument can create a more compelling and meaningful way for them to engage in the practices. Just be sure the judges and students are clear about expectations and preparation, to ensure a fair experience for everyone.
You can have students prepare their arguments during class time or assign as homework.
