During the last two weeks, we did a lab where the students designed and built water filters. To me, this lab seemed much more successful than the earthquake lab, and I usually left the school at the end of the day feeling good about what we did. This lab was designed to take less time than the previous one, and the students' tasks were simpler than in the earthquake lab (thanks to experience and some tips from Lucie Howell). I also completely cut out the powerpoint, which I think was a good move with this age group. This was again a two-day lab, and I spend Monday and Tuesday of last week with Mrs. Buckwalter's classes and Monday of Tuesday of this week with Mrs. Karalash's classes.
Day 1 began with me starting a discussion with the class about drinking water. I asked "who drinks water?" and usually everyone raised their hands, so I followed it up with "where does that water come from?" I got a variety of answers to this question (which was what I was hoping), with answers ranging from "the ocean", "the lake", "wells", "rain", "the faucet", and "the Ypsilanti Community Utilities Authority." Regardless of this, I tried to get it all back to the fact that our water in Michigan typically comes from the Great Lakes, which are the largest source of fresh water in the world. I then transitioned the conversation toward the water cycle (precipitation, evaporation, condensation), which I drew on the board. We talked about how nature cleans water through evaporation and how the dirtiest part of the water cycle (runoff and rivers/lakes) is where we get our water, which means we need a good way to clean water.
Usually around this point I would pass out the Day 1 worksheets, which had 3 questions on them that we answered together and space for two drawings of filter designs. We then passed out the materials, which were a two-liter bottle with the bottom cut off, gravel, sand, cotton balls, rubber bands, cheesecloth, coffee filters, and masking tape. In Mrs. Buckwalter's classes we didn't have the sand, and in Mrs. Karalash's classes we didn't have rubber bands. The students were asked to draw and label two different ideas for filter designs, and then as a team of 3-4 students pick one and build it. I passed out some dirty water (manufactured with water and potting soil) for the students to experiment with for the rest of the hour (usually around 15-20 minutes), and at the end of the hour they packed up their materials and put them away for Day 2.
Day 2 started out with the students retrieving their materials and having about 15 minutes to rebuild their best design and make a detailed drawing of that design. Once the students were ready, we tested the filters, and one at a time the teams came up, explained their designs, and I poured dirty water in and we watched the cleaner water come out. At the end, all of the cups of "clean" water were lined up, and we decided who had the cleanest water. If there was a tie, we went with the team that had the most water won (since they all had thirty seconds with the exact same amount of water). We congratulated the winning team, and we talked a little bit about what seemed to work about their filter. Mrs. Buckwalter asked her classes to vote on which material they thought was the best filtering device, which I thought was a nice idea, but must've forgotten for Mrs. Karalash's classes. We then had the students clean up their filters, throwing everything away except for the bottles, which they cleaned up for me for later use. When there was time at the end, we showed the students some videos. Mrs. Buckwalter had found a video about the Central African Republic that highlighted some of the problems with water shortages and their health impacts in that country. In Mrs. Karalash's classes, I brought in a couple of videos about engineering solutions to help regions with water shortages, one of which was from U of M (the Wheelo) and the other from a competition called "Innovate or Die" (the Aquaduct). The students were surprisingly engaged in watching these, and I was really happy with that.
Overall, I think this was a successful activity for the seventh grade students. It was simple, we didn't bore them too much, and they got a chance to build and experiment on their own. The competition didn't really have any real prize (we gave the winners a certificate), but the students still wanted to win. Naturally, there were always a few students who didn't seem to care or who disagreed with their teams, and there were several students who would wander around the room and see what other teams were doing; surprisingly, most of these side conversations were still about the project, which I thought was great. I would recommend this lab activity for this age group in the future.
