Hands-on Activity Is It Safe to Drink?

Learning Objectives

After this activity, students should be able to:

• Ask a question about the world and formulate an orderly plan to investigate it.
• Arrange the steps of a scientific problem in a logical order.
• Design and conduct a scientific investigation.
• Use data to construct a reasonable explanation.

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

Common Core State Standards - Math

International Technology and Engineering Educators Association - Technology

State Standards

Materials List

For the teacher:

• 1 gallon bottle
• 1 bag potting soil

Each group needs:

• 2-liter bottle with base cut off and no cap
• 2" x 2" piece nylon stocking or cheesecloth
• rubber band
• 4 oz cup course sand
• 4 oz cup aquarium gravel
• small coffee filter
• large bowl, approximately 2"– 3" deep
• empty 12 oz cup, to be later filled with dirty water

Worksheets and Attachments

Introduction/Motivation

(As necessary, revisit/reread the storyline, as presented in Lesson 5, reprinted below.)

Even though hunting has been slow, you have been able to survive the dangers of the Amazon rainforest on the plants and insects you and your colleagues have collected. But time is an important factor, especially since the pilot needs medical attention. You continue on your quest to find Manaus with the hope that each day will bring you a little closer.

"Hey guys, we are almost out of water," you hear Julie say. According to the map, several pools of water are nearby. Maybe some of the water is good enough to drink. You realize that testing the water will be hard with the tools you have and you worry about how to filter the water in case it isn't safe to drink. Or perhaps Julie, a chemical engineer, can come up with an idea for a filter design. What will you use? Will it work?

Procedure

Background

In general, filters perform best when the material porosity graduates from the bottom to the top by the smallest to the largest openings that the water can pass through (for example, placing gravel as a first layer and a coffee filter as the last material layer.) This helps to keep the smaller openings unclogged by filtering out the larger particles in the water first, at the beginning of the process.

Before the Activity

• Gather materials and make copies of the Student Guide Worksheet.
• Prepare the plastic bottles. Use scissors to cut the bottom off the 2-liter bottle. Use masking tape to cover the resulting sharp plastic edge, to protect students. Remove any labels from the 2-liter bottle. Repeat this procedure on the rest of the 2-liter bottles for the teams.
• Make a class supply of "dirty water." Fill the gallon bottle three-quarters full with water. Use potting soil to fill the remaining one-quarter. Shake the bottle. Then shake it again a few minutes before the activity since the soil will settle after time. A gallon of water is more than sufficient for the entire class.

With the Students

1. Review with students the scenario provided in the Introduction/Motivation section.
2. Pass out the worksheets and materials to groups composed of three students each.
3. Show students the bottle of "dirty water." Ask them: Who would want to drink this water? Explain to students that their team challenge is to find a fast and effective way to filter the water so it is clean enough to drink.
4. Filll each group's empty 12 oz cups with "dirty water." Remind students to never drink this water, even after filtering.
5. With the worksheet as a guide, have students complete the engineering challenge. Remind them of the basic steps of the engineering design process: understand the need, brainstorm different ideas, select the best design to fit the circumstances and constraints, plan, create and improve.
6. After answering the worksheet questions, have students turn them in for grading. Lead a class discussion to compare results and conclusions. Students may find that a more "scientific filter" (that is, one using sand and gravel) is slower and does not work as well as one using a coffee filter, or gravel and a coffee filter. Discuss with students their different designs and compare the good and bad points about their filter designs. Example successful points: the filter worked very quickly and the water looked much better than before. Example negative points: the filter took a very long time to filter and did not do a good job of removing particles.
7. Conclude by asking the questions provided in the Assessment section to link the activity back to the Amazon scenario.

Assessment

Worksheets: Have students use the worksheet to guide them through the experimental procedure and turn them in for grading. Review their answers to the worksheet questions to gauge their comprehension.

Wrap-Up Questions: At activity end, ask the students the following questions in an open, teacher-lead discussion. The questions help to link the activity back to the Amazon scenario. (Note: These questions are not on the worksheet.)

• How much water does your team need to purify? How much water do you think each person in your team will drink? (Answer: In situations like this, a person would drink about 2 quarts of water each day. You may wantn to have students calculate how much water that would be for the entire team each day.)
• Would you be able to build something like this in the Amazon? (Answer: A filter like this would be easy to build and, by boiling it, the water could be drinkable.)
• Would the filter last long enough for you to get to Manaus? (Answer: A filter like this would only work a few times, but it might last a day or two.)

Activity Extensions

Have students research other options for collecting water. A few examples: Many vines can supply pure water simply by being cut open and drained. Other vines provide a poisonous liquid. Bromeliads collect rainwater that might be much cleaner than water found in a pool on the ground.

Have students relate this obstacle to their own lives. How does water get to your homes? What filtering processes are used every day to make sure that your water is safe to drink? If you were an engineer, what additional methods would you use to make the water safe? If possible, take a field trip to a wastewater processing plant. Talk to the engineers and technicians about the processes that they use to filter and clean the water. What happens to the water after it is cleaned?

Investigate the rainfall in your area. Place a rain gauge outside the classroom for a week or two and track the amount of water each day. How do your results compare with published average rainfall for your area? How do they compare with published values for rainfall in rainforests? Have students mark off on a rain gauge diagram the level of the water each day. Also have them mark what the level of water would be if they were in the rainforest. Note the differences at the end of the week.

Discuss survival in different climates. What differences in survival techniques would you be forced to use if you were stranded without water in your own climate? What differences if you were stranded in the desert? Would your water filtering methods change in different environments? Why or why not?

Activity Scaling

For lower grades, do the activity by building a filter as a class. If students suggest several ways they think the materials should be layered, then build two or three different filter designs and test them as a class.

Copyright

Supporting Program

Acknowledgements

Adventure Engineering was supported by National Science Foundation grant nos. DUE 9950660 and GK-12 0086457. However, these contents do not necessarily represent the policies of the National Science Foundation, and you should not assume endorsement by the federal government.