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Lab Report on Osmosis of an Egg
Objective of the Experiment
The overall objective of the experiment is to understand the osmosis process, and the effect of solute concentration on the process.
Introduction
Transport between membranes can be either passive or active. Passive transport involves the movement of substances through a membrane with zero energy requirements by the cell, whereas, active transport is the movement of substances across a membrane that expends cellular energy. For the purpose of this report, the emphasis will be on passive transport. The two main passive transport systems are diffusion and osmosis. Diffusion involves the movement of molecules through a membrane from a region of higher concentration to a region of lower concentration. Osmosis is the movement of solvent molecules through a semi permeable membrane into an area of higher solute concentration (Cath 172). The process is dependent on osmotic pressure, which can be defined as the pressure needed to maintain an equilibrium state between the membranes. In general, the solvent shifts from a hypotonic, less concentrated, to a hypertonic, more concentrated, solution (Myers 334).
For the purposes of this study, the movement of water molecules across a membrane will be experimented using a demineralized egg. This is achieved by soaking an uncooked egg in vinegar for 24 hours. Vinegar contains acetic acid that reacts with the calcium carbonate found in the eggshell to produce a calcium acetate, water, and carbon dioxide (Magloire 228). The reaction can be summed up by the following equation.
2 CH3COOH + CaCO3 (CH3COO) 2Ca + CO2 +H2O
Osmosis is dependent on the concentrations of the solutes between the membranes. In general, tonicity is the study of comparing the concentrations of solutes inside and outside the membrane. There are three types of concentration types, tonicity. First, an isotonic solution is one where the concentration of the solvent is equal on both sides of the membrane thus no movement of water molecules. This means that the two sides have neutral concentration. As a result, there will be no movement of any solutions on either sides of the membrane. Second, a hypertonic solution is one where the solute particle concentration is higher than that of the solvent across the membrane. This leads to the movement of water molecules hypertonic solution. Lastly, in hypotonic solution water shifts away from this solution to amore concentrated one (Myers 345).
Hypothesis
If the concentration of the solvent surrounding the egg is higher than the egg’s cytosol then water will shift away from the egg to the solvent leading the eggs’ loss in weight.
Materials
The materials used in this exercise were three raw eggs in a shell, measuring glass, an overflow bowl, a spoon, nine covers with lids, white vinegar, light corn syrup and a gallon of distilled water.
Procedure
First, the three eggs were put in containers containing vinegar undisturbed for 48 hours to demineralize the eggs. The demineralized eggs were later cleaned up and the initial egg volume of each egg was determined. It is not difficult to measure the volume of the egg; only water and a measuring a jar are required. Using these materials, the volume is achieved by filled with water up to the half a liter mark. In this case, the egg is immersed on the jar and the water level is measured again. The difference in measures before the egg was immersed and after the egg was immersed, is the volume of the egg. On the other hand, if there is no measuring jar one can use a displacement cup with water. The displace cup is filled with water and then the egg is immersed. The displaced water is taken and measured. the displaced water should be measured since it is the volume of the egg.
The next step involved pouring 1 cup of measured syrup into three separate jars. The jars should be labeled according to the labeling of the solids for easier identification. In this case, the jars were labeled A for the one with the syrup, B for the one with distilled water. Egg A, in jar A, was then immersed into the jar and allowed to stand undisturbed for 12 hours and the observations recorded. The volume of the egg was measured to note if there were any changes in volume. The results of the measurement were recorded as T0. The egg volume is then measured after time intervals of 12 hours and the readings recorded. The exercise is done up to T48. Then the egg A was transferred into the jar with distilled water and the exercise carried out up to T72. All the observations and changes were recorded.
The above procedure is then repeated for the other eggs .i.e. egg B and egg C. The average volume of the eggs at each time interval is then calculated. From the data obtained, a graph of time against the egg volume is then calculated in Microsoft Excel spreadsheet.
Results
The results obtained were recorded in Microsoft Excel spreadsheet that is attached to this report. A summary of these results are as follows
Table 1:
| T# | Egg ID | initial volume of water in measuring cup (per cups) | volume of water and egg (per cups) | (volume of water and egg –initial volume of water) =
volume of egg (per cups) |
| T0 | Egg A | 1 | 1.375 | 0.375 |
| T0 | Egg B | 1 | 1.375 | 0.375 |
| T0 | Egg C | 1 | 1.375 | 0.375 |
| T12 | Egg A | 1 | 1.25 | 0.25 |
| T12 | Egg B | 1 | 1.25 | 0.25 |
| T12 | Egg C | 1 | 1.25 | 0.25 |
| T24 | Egg A | 1 | 1.1875 | 0.1875 |
| T24 | Egg B | 1 | 1.1875 | 0.1875 |
| T24 | Egg C | 1 | 1.1875 | 0.1875 |
| T36 | Egg A | 1 | 1.125 | 0.125 |
| T36 | Egg B | 1 | 1.125 | 0.125 |
| T36 | Egg C | 1 | 1.125 | 0.125 |
| T48 | Egg A | 1 | 1.0625 | 0.0625 |
| T48 | Egg B | 1 | 1.0625 | 0.0625 |
| T48 | Egg C | 1 | 1.0625 | 0.0625 |
| T60 | Egg A | 1 | 1.4375 | 0.4375 |
| T60 | Egg B | 1 | 1.4375 | 0.4375 |
| T60 | Egg C | 1 | 1.4375 | 0.4375 |
| T72 | Egg A | 1 | 1.5 | 0.5 |
| T72 | Egg B | 1 | 1.5 | 0.5 |
| T72 | Egg C | 1 | 1.5 | 0.5 |
Table 2:
| Time | Average Mass of Eggs ( per cups) |
| T0 |
0.375 |
| T12 | 0.25 |
| T24 |
0.1875 |
| T36 |
0.125 |
| T48 |
0.0625 |
| T60 |
0.4375 |
| T72 |
0.5 |
Discussion
The results of the experiment show the reduction in mass of the egg when soaked in syrup i.e. from T0 to T48. However, the volume of the egg increases when the egg is submerged in distilled water i.e. from T60 to T72. This is explained by the fact that when syrup is compared to the egg, syrup has a higher concentration as compared to the egg. As the theory of osmosis dictates, solutes will move from a region of low concentration to a region of higher concentration. For this reason, the mass of the egg continued to decrease as the time decreases.
On the other hand, when the egg is immersed in distilled water, there is increase in volume. This can be attributed to the fact that distilled water has a lower solute concentration as compared to the egg. This necessitated the movement of water molecules by osmosis through the eggs’ membrane. This indicates that water molecules moved from a region of lower water molecules concentration into a region of higher water molecule concentration.
Conclusion
The objective of the experiment was achieved as the process of osmosis was well understood and effects of solvent concentration on the process were. From the experiment, it was evident that water molecules shifted from an area of high water molecule concentration to an area of low water molecule concentration. For instance, when the egg was immersed into the syrup, water molecules shifted from the egg resulting in reduction in its weight. The reverse is also true as was the case for distilled water. In addition, the hypothesis of the experiment was established to be correct. The egg lost weight when immersed in syrup this is because the syrup was hypertonic to the solution inside of the egg, leading to water molecules moving from the egg to the surrounding solvent.
In this case, the experiment met its purposes by proving the theory of osmosis. If the results were otherwise, the experiment could not have met its purpose. It was worth noting that there are similar experiments but they use different materials. Additionally, there are different experiments processes with different materials explaining the same concept of osmosis. Therefore, for those who are planning to perform a similar experiment should also try to use other materials or other procedures to come up with conclusive evidence to prove the validity of the theory of osmosis.
Works Cited
Cath, T Y, A E. Childress, and M Elimelech. “Forward Osmosis: Principles, Applications, and Recent Developments.” Journal of Membrane Science. 281 (2006): 70-87. Print.
Magloire, Kim. Cracking AP Biology Exam. New York: Random house, 2004. Print.
Myers, Richard L. The Basics of Chemistry. Westport, Conn: Greenwood Press, 2003. Print.
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