Discussion
In my hypothesis, I predicted that if diffusion and osmosis across a selectively permeable membrane are related to the substance the membrane is submersed in, then an egg submersed in salt water will shrink as a result of the diffusion of water for in and out of the egg, while an egg submersed in plain or coloured water will expand. However, my hypothesis was only partly supported by the results as the egg submersed in salt water (Egg 2) expanded, rather than shrunk, gaining 4.9g and absorbing 25mL of water, although the egg submersed in coloured water (Egg 1) did indeed expand, by 14.4g, also absorbing approximately 25mL.
In my experiment, I submersed two eggs in coloured and salt water respectively. Salt water was used as a hypertonic solution as there was supposed to be more solute (salt) than solvent (water). Coloured water was used as a hypotonic solution as there was less solute (dye) than solvent (water). The effects of the different solutions on eggs through diffusion and osmosis could then be tested, as the concentration of water was the independent variable, and the effects of the varied concentration the dependent variable. The eggs themselves were of a similar volume and mass, as well as the beakers, for they were of the same size and filled with the same amount of water. Also controlled was the temperature of the eggs, as they were refrigerated in the same fridge. Therefore, all variables were controlled.
After the eggs were removed from the substances, some differences were apparent. In Table 1, it describes how the Egg 1 changed colour from brownish-white to bright pink, expanding and cracking, while Egg 2 remained brownish-white, but also cracked and expanded, although less so than Egg 1. Table 2 and Graph 1 display the gain in mass for each egg – a transition from 52.8g to 67.2g (14.4g gain) for Egg 1 and a transition from 57.4g to 63.3g (4.9g gain) for Egg 2, meaning that while both gained in mass, Egg 1 gained much more. In Table 3 and Graph 2 it can be seen that both eggs absorbed approximately 25mL, as that is the approximate amount of water no longer in the beaker after 24 hours elapsed. The precise amount could not be determined as the beaker had vague lines of measurement. Egg 1 expanded the most as there was a very low concentration of solute within the water, and there was a higher concentration within what water there was in the egg than the large amounts of water outside the egg. As there was a lower concentration of water inside the egg than outside, the water went through osmosis and passed through the egg’s membrane, in attempts to achieve equilibrium where the concentration and amount of water would be equal inside and outside of the egg. The dye particles did not affect the inside of the egg, as there was a high concentration of solute within the egg and the dye would not diffuse into an area with higher concentration. As the salt water was a hypertonic solution, there should’ve been a higher concentration outside the egg, causing water particles to go through osmosis and pass through the egg’s membrane to outside the egg in order to balance out the concentrations, causing the egg to shrink. However, it did not shrink, potentially because the salt water did not have enough salt (solute within it), and thus was not a hypertonic solution, causing the egg instead to expand based on what happened to Egg 1. It would’ve expanded less as there was a greater amount of solute within the solvent, but still not enough to become a hypertonic solution rather than a hypotonic solution.
The experiment was unsuccessful as there appears to be an error in the substances as the salt water was not a hypertonic solution as it was supposed to be. In future, I would ensure that it was a hypertonic solution by using a thicker liquid such as molasses that clearly had a very high concentration. If I repeated the experiment I might also test the effects of different amounts of a substance for an egg to be submersed in.
In my experiment, I submersed two eggs in coloured and salt water respectively. Salt water was used as a hypertonic solution as there was supposed to be more solute (salt) than solvent (water). Coloured water was used as a hypotonic solution as there was less solute (dye) than solvent (water). The effects of the different solutions on eggs through diffusion and osmosis could then be tested, as the concentration of water was the independent variable, and the effects of the varied concentration the dependent variable. The eggs themselves were of a similar volume and mass, as well as the beakers, for they were of the same size and filled with the same amount of water. Also controlled was the temperature of the eggs, as they were refrigerated in the same fridge. Therefore, all variables were controlled.
After the eggs were removed from the substances, some differences were apparent. In Table 1, it describes how the Egg 1 changed colour from brownish-white to bright pink, expanding and cracking, while Egg 2 remained brownish-white, but also cracked and expanded, although less so than Egg 1. Table 2 and Graph 1 display the gain in mass for each egg – a transition from 52.8g to 67.2g (14.4g gain) for Egg 1 and a transition from 57.4g to 63.3g (4.9g gain) for Egg 2, meaning that while both gained in mass, Egg 1 gained much more. In Table 3 and Graph 2 it can be seen that both eggs absorbed approximately 25mL, as that is the approximate amount of water no longer in the beaker after 24 hours elapsed. The precise amount could not be determined as the beaker had vague lines of measurement. Egg 1 expanded the most as there was a very low concentration of solute within the water, and there was a higher concentration within what water there was in the egg than the large amounts of water outside the egg. As there was a lower concentration of water inside the egg than outside, the water went through osmosis and passed through the egg’s membrane, in attempts to achieve equilibrium where the concentration and amount of water would be equal inside and outside of the egg. The dye particles did not affect the inside of the egg, as there was a high concentration of solute within the egg and the dye would not diffuse into an area with higher concentration. As the salt water was a hypertonic solution, there should’ve been a higher concentration outside the egg, causing water particles to go through osmosis and pass through the egg’s membrane to outside the egg in order to balance out the concentrations, causing the egg to shrink. However, it did not shrink, potentially because the salt water did not have enough salt (solute within it), and thus was not a hypertonic solution, causing the egg instead to expand based on what happened to Egg 1. It would’ve expanded less as there was a greater amount of solute within the solvent, but still not enough to become a hypertonic solution rather than a hypotonic solution.
The experiment was unsuccessful as there appears to be an error in the substances as the salt water was not a hypertonic solution as it was supposed to be. In future, I would ensure that it was a hypertonic solution by using a thicker liquid such as molasses that clearly had a very high concentration. If I repeated the experiment I might also test the effects of different amounts of a substance for an egg to be submersed in.