- 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.
- 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.