ALEX Lesson Plan

This lesson uses hands-on activities to discuss water filtration. Students will have the opportunity to explore water filtration by filtering water through a variety of materials and using potatoes to grow and test the bacteria levels of the water.

With a focus on nanotechnology, this lesson discusses the benefits of embedding silver ions in filters to kill harmful bacteria. At the end of this lesson students will have the opportunity to put their knowledge to the test in a written discussion by designing a solution to a mock water crisis.

This module was authored by the Auburn University NanoBio MSP Fellows Will Haynes, Chelsea Lindskog, Hannah Taylor, and Catherine Wolfe under the supervision and guidance of Drs. Virginia Davis and Chris Schnittka.

• Pens/Pencils
• Notebook paper (for recording responses)
• Russet Potatoes (number depends on class size and amount of slices needed per group, do not cut the potato slices too thin- 2-3 mm slices should be fine)
• Yogurt (1 ~5oz. cup, make sure live cultures are present, this is for mixing with water to guarantee bacteria is present)
• Clear plastic cups (16 oz.) (must be clear so water can be seen through the plastic)
• Funnels (that best fit the plastic cups)
• Cheese cloth, Kitchen  towel, Flour sack towel, Filter paper, Washcloth, Coffee filter
• Silver nitrate
• Glucose
• Sterile Petri dishes or Tupperware (for holding/storing potato slices)
• Tweezers (for dipping potatoes)
• Glass Beaker
• Microwave
• Access to water
• Dirt (Best to dig dirt from outside. Potting soil may be too sterile.)
• Water (to fill the cups for each group)
• Rubbing alcohol/alcohol wipes (to sterilize Petri dishes or Tupperware as needed)
• Mylar balloons (enough for each group of students)
• Latex balloons (enough for each group of students)
• Garlic (two cloves per group)

• Computer
• Microsoft PowerPoint
• Projector and interactive whiteboard

Before the lesson teacher should:

• Cut potatoes into thin slices (2-3mm)
• Boil potato slices for 2 minutes
• Disinfect the Petri dishes or Tupperware with rubbing alcohol/alcohol wipes. If rubbing alcohol is used, very little is needed. Just enough to coat the dish. Let the petri dish dry before using.
• Store the potato slices each in their own Petri dishes or Tupperware containers
• Create silver paper by using the attached guidelines

For safety concerns, students should NOT:

• cut potatoes
• boil potatoes
• eat potatoes
• wear open-toed shoes
• touch the bacteria colonies on potatoes
• consume any water or food in the lab or that was used in the lab

Lesson:

• Go through each slide of the PowerPoint with students
• At slide 12 there is a video on the drinkable book. Take time to watch that with your students to get them thinking about water filtration. The Water is Life website is optional and there if you and/or your students would like to know more. 
• At slide 16, watch the Nano video to better the students' understanding of nano and go through the interactive nanoscale graphic with the link provided on the slide to show students how small nano really is. At this time, you could go through the nano handout as well. 
• Slide 17 has another video that talks about nanotechnology and why the students should care about it.
• Slide 27 has the cell size and scale link again to look at the size of bacteria if you would like. 
• Slide 29 contains a real life video of silver ions killing bacteria.
• At slide 32, stop the PowerPoint and do the Mylar and latex balloon activity

Mylar and latex balloon activity:

• Each group of students (2-4 students) will receive one Mylar balloon, one latex balloon, and two cloves of garlic.
• Students will put a clove of garlic into each balloon and seal/tie it shut.
• Students will then crush the clove of garlic inside the balloon without puncturing the balloons.
• Students will then observe which balloon they can better smell the garlic from and relate that to the permeability of a bacterial cell after it is attacked by silver ions.
• At slide 40/41, stop the PowerPoint to do the water filtration activity with the students

Water filtration activity:

• Students will be split into groups (2-4 students per group). It is up to the teacher’s discretion how many filtrations are done per group and which filtrations are done per group. (i.e. one group focuses on the coffee filter and yogurt water and one group focuses on dirty water and silver paper, etc.)
• Each group will obtain one cup of dirt, a tablespoon of yogurt, and some water. Each filtration needs enough water in the initial dirtied water cup to fill the secondary cup enough to where results can be seen. One cup of water (8 oz.) should be enough.
• Each group will mix the dirt, yogurt, and water.
• The teacher can decide if each group will pour the dirt water through each of the filters (cheese cloth, flour sack, kitchen towel, dishcloth, coffee filter, filter paper, and the silver filter paper) or if he or she would like to do it as a class and discuss the outcomes as a class. Expected outcomes are on slides 42-45 and discussion questions are on slide 41.
• Using tweezers, each group will dip potato slices into different types of water. For example, one group could do regular tap water, one group could do water that was filtered through a kitchen towel, and one could do the dirty water that was not filtered through anything. This is up to the teacher. Some factors that might help a teacher decide would be group size and time constraints. If there is ample time, then a group could do more than one, such as doing one potato slice in a different type of water per person in the group, etc.
• The students will then put their dipped potato slice into the sterile petri dish or Tupperware available. 
• The potato slices will need to be kept in a dry, dark place to rest for 2-3 days.
• On the third day, the students can look at their potatoes and see if their potato grew any bacterial colonies and infer what that meant about the cleanliness of their water and how they could fix the problem.

Closure:

• In conclusion, this week we have learned all about water filtration. We have learned that water can be cleaned through filtration and through nanotechnology. There are some parts of the world that do not have access to clean water and these procedures could potentially help those people. We learned that silver ions can kill bacteria in two ways, by first making the bacteria’s membrane more permeable and secondly inhibiting the bacteria’s metabolism. The bacteria we saw grow on the potatoes demonstrated how important filtration is and how it can help eliminate bacteria.
  • If the teacher would like he or she could do an exit activity, but there is a post test, the water crisis discussion, and a crossword puzzle as well.
  • Suggestions for an exit activity if desired:
    • Students write open-ended questions on index cards. A few students are selected to come forward. The first student draws a question card and poses the question to the class. After the class discusses the question and answers with their partner - the second student draws a student name card to respond to the question, etc.
    • 3-2-1 Exit Ticket: Students write down three things they learned, two things they still are not sure about, and one thing they still do not know, or would like to know more about.

Pre-test and Post-test Activity.

Options for Assessment: See Extension section for additional assessment options for the post-test activity. 

Each group may create a poster to inform the public about their water crisis plan that they came up with in the post-test scenario and try to convince the public to support it, like a campaign poster with a catchy slogan.

Students could have a mock town hall meeting where two groups at a time debate and defend their plans in order to decide which plan the city or country will use.