In this lab, we took two eggs, dissolved the shells in vinegar, and then put one egg in deionized water, and the other one in sugar water. Before putting them in, we measured their masses and circumference around the middle of the egg the short way. We left the eggs in their solutions, and after 48 hours, we removed them and remeasured the circumference and mass of each. Based on the class averages, the eggs put in deionized water grew in both mass and circumference, and the egg that was put in the sugar water shrunk significantly in both mass and circumference. This happened due to the process of diffusion. Diffusion is when molecules enter a cell through the cell membrane. The water went through osmosis, which is a type of passive diffusion which uses no energy. Usually in diffusion, molecules move from an area of high concentration to low concentration. But in osmosis, the solvent of a solution goes from an area of low concentration to high concentration. In solutions, the solute can't pass through the membrane, but the solvent, such as water, can, so it will move to an area of high solute concentration, which will have a lower solvent concentration. Solutions with more solute than inside the cell are hypertonic, such as the sugar water. When the egg was placed in the sugar water, there was more solute outside the cell than inside, so water left the egg to where there was more solute, which decreased the mass by an average of -51.7% and decreased the circumference by an average of -23.67%. This is a good example of how a cell reacts to the outside environment. When we put the egg in the vinegar, the acidity dissolved the eggshell, but also some of the vinegar was absorbed by the cell through diffusion. Then when we put the egg in the water, some of the vinegar left the egg, which explains some of the groups that reported a decrease in mass and circumference. When it was put in the sugar, both the vinegar and the water left the egg through diffusion. Diffusion is important to cells, because they need to get things like water and oxygen to function, which enter through diffusion. Diffusion is a process that you can see daily. In markets, vegetables are sprinkled with water so they don't go limp, because the water diffuses into the vegetables' cells. When salt is used to melt ice on roads, the plants lose water because of diffusion as well. The high concentration of salt in the solution around them cause water to leave the plant cells, which is another example of osmosis. Based on this experiment, I would like to test it on living cells, because this process makes me think of how skin cells wrinkle when in water, which makes me wonder if diffusion is taking places with skin cells.
Deionized Water | | | | | | | | |
Group # | 1 | 2 | 3 | 4 | 5 | 6 | 7 | Average |
% Change in Mass | | -0.54% | -1.47% | 10.50% | 0.74% | -4.20% | -5.10% | 0.18% |
% Change in Circumference | | -2.89% | 0% | 21% | 0% | -12.90% | -4% | 0.20% |
Sugar Water | | | | | | | | |
Group # | 1 | 2 | 3 | 4 | 5 | 6 | 7 | Average |
% Change in Mass | | -49.72% | -55.00% | -52.00% | -49.60% | -52.40% | -56.70% | -51.70% |
% Change in Circumference | | -23.68% | -28% | -21% | -29% | -26.50% | -38% | -23.67% |
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