An egg is a model of a human because the egg has a cell membrane like humans do inside and outside of the body that let things pass through like water. We can use eggs to study the effect of changes in the external environment on the internal environment by having harsh environments like putting the egg in only alcohol and see what happens to the inside of the egg. Diffusion is the movement of a substance down its concentration gradient from a more to a less concentrated area.
Meaning if there was more oxygen on one side of the membrane and the membrane was permeable to oxygen, the oxygen would pass through to the side of less oxygen. Osmosis is the movement of water across a selectively permeable membrane. Diffusion and osmosis is important for organisms because our nutrients, oxygen, and etc., need diffusion to go through compartments. I predicted that the more the concentrated the alcohol solution was the mass would increase because I thought the membrane would let alcohol through which would cause the egg to expand. Materials and Methods:
3 plastic cups
Rubbing alcohol (70%)
1) Gather materials
2) Peel outer shell/membrane off the egg
3) Measure and record the mass of egg
4) Put egg in 300 mL of water ( 0% alcohol)
5) Leave egg in for 24 hours
6) After 24 hours measure and record mass of egg
7) Repeat Steps 2-6 with 150mL of water & 150mL of alcohol (30% alcohol) 8) Repeat Steps 2-6 with 300 mL of alcohol (70% alcohol)
The eggs averaged a mass of 68.5 g before they were in the solutions of alcohol and water. The egg for 0% alcohol (300mL of water) had a mass of 71.7g before 24 hours. The mass after 24 hours in 0% alcohol was 77.3 g. This egg had a difference of +5.7 g or a +7.8% change in mass. The egg for 35% alcohol (150mL of alcohol/150mL of water) had a started mass of 67.7 g. The mass after 24 hours was 66.0 g. The difference of mass was -1.7 g. The
percent change was -2.5%. The last egg for 70% alcohol (300mL of alcohol) had a mass of 66.1 g, when starting. The ending mass was 53.1 g. The mass difference was -13.0 g and had a mass percent change of -19.7 %.
Based on my data, the egg was semi-permeable. I know this because the mass of the egg decreased which should be result of osmosis. For the last egg, the egg was in 70% alcohol which means it didn’t have any water, and the starting mass was 66.1 grams. The ending mass was 53.1 grams. Also I observed that the only thing left inside the egg was the white parts and yellow, which meant all the water from the egg pass through the membrane because the water needed to be equal to the outside environment. Diffusion happened with the first egg which was the one that was only in water.
I know that diffusion happened because the mass of the egg gained which meant water hap to come in because water can’t just magically grow/appear in an object. The mass before putting the egg in water over 24 hours was 71.7 grams. The next day it increased to 77.3 grams. This is diffusion because the water molecules on the outside of the egg were the higher concentration gradient than the ones in the inside so it had to be even. To be equal, the water had to diffuse through the membrane into the egg causing the mass to increase
. The evidence refuted my prediction because I said that the alcohol would increase the mass which was the opposite of my results. The results showed me that alcohol decreases the mass of an egg. Some potential sources of error in my experiment could have been measuring the exact amount of alcohol or water, and/or measuring the correct mass each time. Some ways that my experiment could have been improved are by using alcohol that was at a higher concentration than 70% or being able to control the temperature of the eggs or water/liquids. My experiment creates future experiments of what does alcohol actually do to human cells.