Investigating Osmotic Rates.
Article Type: Product/service evaluation
Subject: Cytology equipment (Product/service Evaluations)
Author: Monsqur, Chris
Pub Date: 08/01/2011
Publication: Name: The American Biology Teacher Publisher: National Association of Biology Teachers Audience: Academic; Professional Format: Magazine/Journal Subject: Biological sciences; Education Copyright: COPYRIGHT 2011 National Association of Biology Teachers ISSN: 0002-7685
Issue: Date: August, 2011 Source Volume: 73 Source Issue: 6
Product: SIC Code: 3841 Surgical and medical instruments; 3845 Electromedical equipment
Accession Number: 265291899
Full Text: Investigating Osmotic Rates. Carolina Biological Supply, $191.

Overview of Product

"Investigating Osmotic Rates" is a hands-on, inquiry-based investigation that allows students to visually explore many of the aspects that affect osmosis and diffusion, with particular focus on osmotic rates. While it is intended for both the high school and the college level, it is likely best suited for the introductory college laboratory. It is designed to help students understand the fundamental advanced aspects of osmosis and diffusion. The class, divided into different expert teams, has the opportunity to investigate effects of solute concentration on osmotic rate, electrolytes versus natural solutes, and the effects of enzymes on osmotic rates. After completing the investigations, each expert team shares their results with the rest of the class for discussion and comparison. Students then analyze pooled results by creating a master graph looking at the impact on osmotic rate and then reflecting upon a series of higher-order questions.

Learning Goals & Standards

Carolina Biological continues to create high-quality educational products, and this is clearly evident when one opens the teacher's manual. The National Science Education Standards are clearly outlined, and a brief overview of what students are expected to do and how they will be assessed is provided. If you're a teacher who has to document every standard covered in each lesson plan, Carolina has done a great job of including these in the teacher's manual. The manual was clearly designed to be practical and to assist the teacher in implementing the activity and reducing preparation time. Copy-ready student activity sheets and teacher preparation pages have been well designed to maximize the lab experience while reducing overall preparation time. To help teachers and students get the most out of this inquiry experience, safety notes, background information, detailed materials lists and preparation notes, and extension activities are provided.

Materials & Preparation

This compact kit comes packaged in a box for easy storage until you're ready to implement this inquiry in the classroom. Compared to typical osmosis activities that I have utilized in the past, I found this investigation relatively simple to prepare and was able to set up all three stations in about 30 minutes. The reusable osmometers feature genuine animal membrane that is freely permeable to water and dissolved inorganic salts, but not to large molecules. Carolina provided all the essential materials except for a few items such as markers and paper towels, which can be found in most science classrooms.

Instruction

Carolina has designed this kit around the 5E model of instruction: engage, explore, explain, extend, and evaluate. I had my class of 23 divide into six teams of 3-4 students per experimental team (the kit was designed for classes of up to 36). Two student research groups were then assigned to each of the three primary investigations. This created expert groups for each of the three investigations that could collaborate with each other, verify observations and data, and then report back their results to the entire class for discussion.

My high school freshman students were excited to tackle their assigned investigations. To help prepare the students the day before the lab, it is important to have each research group review their procedure carefully. I have only 50 minutes of class time, so it was important to instruct each lab group on how to divide the experimental set-up procedures so they could work collaboratively to get their experiments running. It quickly became clear that students would have some set-up problems, such as leaking osmometer stems or difficulty filling the osmometer properly - issues that must be solved as a group. While this created a realistic investigative experience for my student researchers, I would suggest demonstrating the assembly and set-up of the osmometer to help reduce student errors.

Once the groups have each of the three experiments running, data are collected at regular intervals over a 7-hour period to increase reliability. During this time, the quantity of solution in the osmometer stem steadily changes and students record movement with the stem in millimeters per hour. Compared with other osmosis labs that I have conducted with my students, "Investigating Osmotic Rate" was more visible and, thus, more meaningful to my students. To be able to collect data over the 7-hour period, students needed to take turns measuring changes in the osmometer throughout the day so that adequate data could be collected. This proved to be a limiting factor in my school's seven-period day; it likely would work better for those teaching in block format or at the college level. In addition, collecting 7 hours of data was possible only for classes that started the experiment at the beginning of the day, but this issue could be solved by sharing experimental data from classes throughout the day.

Among the strongest components of this kit are the extension activities. In the first extension activity, the students expanded on their initial experimental observations by testing the permeability of urea and urease, which is indicated by a color change. Then, in the second, the students were able to evaluate the impact of temperature on osmotic rate.

Summary

Overall, I was impressed with the development of this kit. Carolina Biological has creatively taken the abstract concept of osmosis and allowed students to visualize this fundamental process in a way they can understand. I found the content to be accurate and developed in a way that promoted my students' understanding of osmosis and diffusion. My students were excited by the visual approach that Carolina created in this kit; however, collecting data over a 7-hour period can be a limiting factor for many high school educators, depending on their daily schedule. I believe that this kit would be well suited for observations of the rates of osmosis and diffusion at the college level, with longer lab periods and less limiting schedules. The kit included assessments based in higher-order questioning that helped me to determine whether there was increased student learning. Finally, and most importantly, the students not only measured the rate of osmosis, they were able to see osmosis and diffusion taking place.

Lance Brand

Delta High School

3400 E. State Road 28

Muncie, IN 47303

lbrand@delcomschools.org

DOI: 10.1525/abt.2011.73.6.13mho

CHRIS MONSOUR is a teacher at Tiffin Columbian High School in Tiffin, Ohio. He earned a B.S. in Environmental Biology and an M.A. in Education, both from Heidelberg University, Tiffin, Ohio. His interests include nature photography, travel, and camping and hiking. His address is Tiffin Columbian High School, 300 S. Monroe St., Tiffin, OH 44883; e-mail: chris_monsour@tiffin.k12.oh.us.
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