Osmosis Lab Report
Osmosis & Diffusion Lab:
AP Biology Mod 5
Abstract:
The relationship between osmosis and the concentration of glucose was tested with pieces of potato and plastic bags. The relationship was examined by weighing the plastic bags and pieces of potato before and after soaking in water with a varying degree of glucose. Most of our data was not accurate, but we determined that osmosis occurs when an object with a semipermeable membrane is surrounded by water. A higher concentration of water, made possible by glucose, is equally dispersed throughout the solution, therefore making the plastic bag and piece of potato heavier.
Intro:
In this lab, the concept of osmosis was tested through experimentation. Osmosis is the diffusion of water across a semipermeable membrane. (Diffusion) The flow of osmosis depends on whether the object is hypertonic, hypotonic or isotonic. Hypertonic means that the cell’s surrounding are of greater concentration than inside the cell. Hypotonic means that the cell’s surrounding have a lower concentration than inside the cell. Isotonic means that the cell’s surrounding have the same concentration in the cell. (FILTRATION, DIFFUSION, AND OSMOSIS)
The main objective of this lab was to test osmosis with different materials. One experiment included a plastic bag filled with water and it’s surroundings filled with water and different concentrations of glucose. The second experiment tested bits of potato placed in water with unknown concentrations of glucose. We discovered the percent difference in the plastic bags and potatoes by weighing both before and after the experiment. Together, these experiments were used to test the degree of osmosis that occured based on the glucose level in the surrounding water.
We hypothesized that the greater the glucose level was, the heavier the bag or potato would be. We came to this conclusion based upon our previous knowledge about hypertonic, hypotonic and isotonic solutions. The higher concentration of glucose in the surrounding water should have made the a hypertonic solution. Because of osmosis and homeostasis, the solution should have balanced out through the semipermeable membrane, therefore making the plastic bag and potato heavier than they originally were.
Methods:
This lab was conducted in a science classroom format, at New Tech High @ Coppell. Our experiment was to test if the masses of the bags filled with a certain amount of water and pieces of the potato would increase or decrease from being placed in 6 different water solutions. We had 4 members in total, the work was evenly divided among four groups of students working in quadrants. Each group contributed to the overall data collected.
We conducted a chart to analyze the difference among the initial and final mass of the bags and potato. We conducted the test to determine (1) if the masses increase/decrease from the different water solutions, and (2) if the masses matches the other groups/teacher’s data.
Discussion:
Osmosis is the diffusion of water moving through a semipermeable membrane for the purpose of balancing out the amount of water on the inside of the cell versus the amount of water on the outside of the membrane. The equipment for the osmosis and diffusion lab was simple because not much is required to test osmosis and diffusion in a substance. The potato core only needed to be placed in different solutions with different solute levels. The hypothesis was that if a potato piece has more glucose than it will have a greater mass due to osmosis.
The simplicity of the lab equipment needed makes the lab design simple as well. For osmosis and diffusion to take place there is time needed to allow water to diffuse over the semipermeable membrane. For that reason, the pieces of potato were left overnight in the different solvents. Next day in class, our results showed that two potato pieces lost mass, one gained mass, and the others stayed consistent in their mass. As far as results, only one potato piece was correct in our hypothesis and the other 5 are not.
During the process, many times it is not seen in certain substances because it does not have very permeable pores which doesn’t allow the osmosis and diffusion process to take place. In the case of the potato, the pores were smaller not allowing as much water through and then the potato doesn’t gain mass as originally hypothesized.
Results:
Water Bag Data
The measurements taken at the study site show that each bag’s final mass was greater than the initial. For the distilled water, the mass difference was 1.3 (Table 1). For the water with .2 m, the mass difference was 1.2 (Table 1). For the water with .4 m, the mass difference was 1.1(Table 1). For the water with .6 m, the mass difference was 1.2 (Table 1). For the water with .8 m, the mass difference was 1.1 (Table 1). For the water with 1 m, the mass difference was 1.1(Table 1). The average percent change was 5.71%. The class average was 16.34%.
Potato Data
The measurements taken at the study site show that each piece of the potato’s final mass was lesser or did not change from the initial mass. For beaker 1, there was no change in mass. For beaker 2 there was no change in mass (Table 2). For beaker 3, the mass difference was .1 with a -33.33% change(Table 2). For beaker 4, the mass difference was(Table 2) .1 with a 33.33% change(Table 2). For beaker 5, the mass difference was (Table 2).1 with a -33.33% difference(Table 2). For beaker 6, there was no change in mass(Table 2).
Conclusion:
The purpose of this lab was to learn about osmosis by soaking the bags filled with a certain amount of water and the pieces of a potato to see if it increase/decrease in weight. We know that osmosis allowed us to demonstrate what a cell would do to balance water within it. With the 1st experiment we learned that our data was very different from others that were doing the same experiment with different bags, but all were semipermeable. We also learned that our 2nd experiment barely had different results than the initial data. There seems to be a fine line among the two experiments which absorbs water differently and that the weight would increase either way to help balance the water inside.
Works Cited:
Diffusion. (n.d.). Retrieved September 11, 2015.
FILTRATION, DIFFUSION, AND OSMOSIS. (n.d.). Retrieved September 11, 2015, from http://instruction2.mtsac.edu/crexach/physiology/pdf phys lab support and supplement/diff filt osmosis.pdf
