Dialysis Lab Report
Analysis During the experiment, a dialysis bag was used to mimic a cell membrane. Two ways why this model realistically represents a cell is because the dialysis bag is semi-permeable, like a cell. The bag was able to allow water in, as the size of the water molecule was small enough to be able to fit through the pores of the bag. Sucrose was not able to pass through as the molecules were too big to enter. This is similar to a cell because the size of a molecule can determine whether or not the substance can enter the cell through diffusion. Larger molecules will require facilitated diffusion, using a transport protein, or active transport, using a transport protein and also ATP (HyperPhysics.edu). Since water can pass through the dialysis
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bag, diffusion can be shown. When the dialysis bag was placed in an unknown solution, water would be able to pass through in order to make the inside of the bag and the outside of the bag isotonic, equalizing the ratio of solution to fluid. The model is limited because the dialysis bag doesn’t have transport proteins. In a cell, there are transport proteins like a channel protein, built into the membrane, that allows for facilitated diffusion. This would allow for sucrose to pass through the membrane. Another reason why this model is limited is because the dialysis bag doesn’t have the properties that a cell membrane has. Even though the dialysis bag was considered semi-permeable in the experiment, it is really not because it can’t actually control what comes in and what comes out. It only decides what comes in because the pores of the bag can fit only small molecules. Regardless of whether or not the dialysis bag is truly semi-permeable, the experiment was able to test the hypothesis. In order to understand the change in mass, the sucrose concentration of the unknown solution was necessary. By analyzing the graph, it was determined that the sucrose concentration of the unknown solution was 10.57%. The substance that is moving and causing the mass to change is water because the bag was permeable to water, not the sucrose solution. The graph’s role in determining the unknown sucrose concentration was the graph gave the trendline, along with the equation for it. The equation was y=1.94x-20.5. By making y=0, I was able to find x, or the unknown sucrose concentration. By adding 20.5 onto both sides, the equation was 20.5=1.94x. 20.5/1.94=10.57. Along with those calculations, the percent change in mass was calculated in order to visualize whether or not the dialysis bag gained mass or not. The bags would gain mass by water diffusing into it in order to reach equilibrium. During the experiment, the bags were weighed initially. Then after a couple hours, the bags were weighed. The percent change in mass was found by subtracting the final mass and the initial mass and then dividing that by the initial mass and multiplying it by 100. The relationship between the percent change in mass and the concentration difference is that when there is a greater amount of water in either the inside or the outside of the bag, then the change in mass will decrease because when a solution has more water, it’s hypotonic to what it’s being compared to, which would be hypertonic. In order to reach equilibrium, the water from the hypotonic solution would have to move to the hypertonic solution, decreasing the percent change in mass. This can be shown with two different dialysis bags with the sucrose concentration 25% and 0%. A bag that gained mass was the bag with 25% sucrose concentration. Due to the fact that is has 25% sucrose, that means it has 75% water.
The outside of the bag has 10.57% sucrose, so it has 89.43% water. Since the outside of the bag is hypotonic to the inside of the bag, which is hypertonic, the water’s net movement will flow into the bag. Also since the dialysis bag’s weight heavily depends on the amount of water, the mass will go up when water is gained. The class average for amount of mass gained was 22.55%. A bag that lost mass was the bag with 0% concentration, which means it has 100% water. The outside of the bag has 10.57% sucrose and 89.43% water. This makes the outside of the bag hypertonic to the inside, resulting in a net flow of water the outside in order to reach equilibrium. By losing water, the inside of the bag will have a lower mass and is shown in the class average of -20.61% decrease in mass. A source of procedural error was that the bags could have possibly leaked the solution because the only way the bags were sealed was with a knot. The solution could have leaked and affected the data by decreasing the mass of the bag. This could be indicated by how mixed the results are. The percentage change in mass in table 1.2 are way off compared to the percentage change in mass, corrected. Another source of procedural error was the location
of the bags. The bags were placed in the beakers overnight, subject to the fluctuations of the temperature. The location decided if a beaker got warmer, speeding up diffusion, or got colder, slowing down diffusion. This is shown in the data of the different classes. Each class and group got different answers and the rate of diffusion plays a part in that.
Conclusion
Diffusion is an important topic in general because it plays a large role in our daily life, it is just hard to notice that it is occuring. “We can smell perfume because it diffuses into the air and into our nose.” (Your dictionary). The reason why soda gets flat after leaving it out for a while is because the carbon dioxide bubbles will diffuse, making the soda flat. Do you always notice how the helium balloons you get for your birthday always eventually lose all its air? Well that’s because the helium in the balloon diffuses from inside the balloon and into the air. In our body, “Oxygen diffuses from the blood cells in the blood stream into muscles.” Diffusion is everywhere, in our body, and all around us. The experiment could’ve been modified the experiment in order to minimize the sources of error. Sources of error were that the water would have seeped out of the dialysis bag, increasing the concentration. Also the class didn’t put the dialysis bags in the beakers at the same time, so our results may have varied because of that, as diffusion might occur faster than others. Another source of error was that the water in the bags could’ve evaporated slightly. This would decrease the possible mass of the bags and skew the results. To prevent these sources of error, we will put the dialysis bags in at the same time and covering the cups to prevent evaporation. A way to modify the experiment in order to learn more about this topic is by changing the temperature of the beakers in order to see how it affects the diffusion time. The temperature changes the speed of particles, so how does it affect diffusion?
bag, diffusion can be shown. When the dialysis bag was placed in an unknown solution, water would be able to pass through in order to make the inside of the bag and the outside of the bag isotonic, equalizing the ratio of solution to fluid. The model is limited because the dialysis bag doesn’t have transport proteins. In a cell, there are transport proteins like a channel protein, built into the membrane, that allows for facilitated diffusion. This would allow for sucrose to pass through the membrane. Another reason why this model is limited is because the dialysis bag doesn’t have the properties that a cell membrane has. Even though the dialysis bag was considered semi-permeable in the experiment, it is really not because it can’t actually control what comes in and what comes out. It only decides what comes in because the pores of the bag can fit only small molecules. Regardless of whether or not the dialysis bag is truly semi-permeable, the experiment was able to test the hypothesis. In order to understand the change in mass, the sucrose concentration of the unknown solution was necessary. By analyzing the graph, it was determined that the sucrose concentration of the unknown solution was 10.57%. The substance that is moving and causing the mass to change is water because the bag was permeable to water, not the sucrose solution. The graph’s role in determining the unknown sucrose concentration was the graph gave the trendline, along with the equation for it. The equation was y=1.94x-20.5. By making y=0, I was able to find x, or the unknown sucrose concentration. By adding 20.5 onto both sides, the equation was 20.5=1.94x. 20.5/1.94=10.57. Along with those calculations, the percent change in mass was calculated in order to visualize whether or not the dialysis bag gained mass or not. The bags would gain mass by water diffusing into it in order to reach equilibrium. During the experiment, the bags were weighed initially. Then after a couple hours, the bags were weighed. The percent change in mass was found by subtracting the final mass and the initial mass and then dividing that by the initial mass and multiplying it by 100. The relationship between the percent change in mass and the concentration difference is that when there is a greater amount of water in either the inside or the outside of the bag, then the change in mass will decrease because when a solution has more water, it’s hypotonic to what it’s being compared to, which would be hypertonic. In order to reach equilibrium, the water from the hypotonic solution would have to move to the hypertonic solution, decreasing the percent change in mass. This can be shown with two different dialysis bags with the sucrose concentration 25% and 0%. A bag that gained mass was the bag with 25% sucrose concentration. Due to the fact that is has 25% sucrose, that means it has 75% water.
The outside of the bag has 10.57% sucrose, so it has 89.43% water. Since the outside of the bag is hypotonic to the inside of the bag, which is hypertonic, the water’s net movement will flow into the bag. Also since the dialysis bag’s weight heavily depends on the amount of water, the mass will go up when water is gained. The class average for amount of mass gained was 22.55%. A bag that lost mass was the bag with 0% concentration, which means it has 100% water. The outside of the bag has 10.57% sucrose and 89.43% water. This makes the outside of the bag hypertonic to the inside, resulting in a net flow of water the outside in order to reach equilibrium. By losing water, the inside of the bag will have a lower mass and is shown in the class average of -20.61% decrease in mass. A source of procedural error was that the bags could have possibly leaked the solution because the only way the bags were sealed was with a knot. The solution could have leaked and affected the data by decreasing the mass of the bag. This could be indicated by how mixed the results are. The percentage change in mass in table 1.2 are way off compared to the percentage change in mass, corrected. Another source of procedural error was the location
of the bags. The bags were placed in the beakers overnight, subject to the fluctuations of the temperature. The location decided if a beaker got warmer, speeding up diffusion, or got colder, slowing down diffusion. This is shown in the data of the different classes. Each class and group got different answers and the rate of diffusion plays a part in that.
Conclusion
Diffusion is an important topic in general because it plays a large role in our daily life, it is just hard to notice that it is occuring. “We can smell perfume because it diffuses into the air and into our nose.” (Your dictionary). The reason why soda gets flat after leaving it out for a while is because the carbon dioxide bubbles will diffuse, making the soda flat. Do you always notice how the helium balloons you get for your birthday always eventually lose all its air? Well that’s because the helium in the balloon diffuses from inside the balloon and into the air. In our body, “Oxygen diffuses from the blood cells in the blood stream into muscles.” Diffusion is everywhere, in our body, and all around us. The experiment could’ve been modified the experiment in order to minimize the sources of error. Sources of error were that the water would have seeped out of the dialysis bag, increasing the concentration. Also the class didn’t put the dialysis bags in the beakers at the same time, so our results may have varied because of that, as diffusion might occur faster than others. Another source of error was that the water in the bags could’ve evaporated slightly. This would decrease the possible mass of the bags and skew the results. To prevent these sources of error, we will put the dialysis bags in at the same time and covering the cups to prevent evaporation. A way to modify the experiment in order to learn more about this topic is by changing the temperature of the beakers in order to see how it affects the diffusion time. The temperature changes the speed of particles, so how does it affect diffusion?