Osmosis Lab Demo

Since my last post I have visited both Mr. Sowder and Ms. Hardy's classes several more times. In Ms. Hardy's class the students were doing a project on careers in science. Each student chose a particular field to study and report on. I worked closely with the student that chose Engineering. He "interviewed" me to obtain much of the information that he was required to find out-- such as the roles/responsibilities of an engineer, where engineers work, salary, and more. I enjoyed working one-on-one with the student, and I think he appreciated being able to talk to someone with firsthand experience rather than just reading about the job. He mentioned that he was interested in Automotive Engineering and that his favorite carmaker is BMW, so I sent him a link describing a current job opening as an engineer at a BMW plant in South Carolina. I also gave him some information about UM's Automotive Engineering Program.


In Mr. Sowder's 1st and 3rd hour classes I led a two-day lesson on osmosis and then performed a lab demonstration using dialysis tubing. This involved a great deal of work but it was very rewarding. 1st hour the students are very sleepy (7:15 is awfully early for teenagers) and 3rd hour they are more awake but still need a lot of prodding to get them involved in the class. Getting the students engaged in the lesson was the most challenging part. In both classes there were one or two individuals that were always raising their hand to answer questions, which is great but at the same time seemed to make the other students less willing to think about the questions because they just figured the other students would answer it for them. On Wednesday I went through the terminology the students needed to learn and had the students help me fill the dialysis bags (our semipermeable membrane) with water and get their initial mass. We placed them in beakers of sucrose solutions of varying concentrations, and I had the students try to form a hypothesis based on their knowledge of osmosis from the lecture. Then on Friday we reviewed the terms and concepts, obtain the final mass of the bags. We calculated the percent change in mass and discussed whether the data supported our hypothesis or not. That was actually a very interesting situation. Of the 4 biology classes that performed this demo, 2 of them came out with very clean data that agreed with what one would expect to happen due to osmosis. However the data from the other 2 classes did not come out this way at all. Mr. Sowder and I talked about whether we should present this data to the students or not, because we were afraid if we did it might confuse them about how osmosis really works. In the end we decided to go ahead and share all the data with them and use it as an opportunity to discuss the different sources of error in the experiment that may have caused the counterintuitive results. We also talked about the need to repeat scientific experiments many times as the data from any one trial may not be reliable. I am very glad we made this decision, as later in the day I attended a lecture at UM about concern over increasing problems with ethics in science and research. I think by presenting the questionable data with the students we were able to teach them a lesson in scientific ethics as well as osmosis.