Introduction:
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:
Materials:
3 eggs
3 plastic cups
Rubbing alcohol (70%)
Distilled water
Scale
Procedure/Method:
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)
Results:
Data Table:
Alcohol Concentration
(%)
Mass Before
(g)
Mass After
(g)
Mass Difference
(g)
Mass Percent Change
(%)
0%
71.7
77.3
+5.7
+7.8%
35%
67.7
66.0
-1.7
-2.5%
70%
66.1
53.1
-13.0
-19.7%
Graph:
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%