Osmosis and the Egg Lab Report
By: N. Mullins
Date: January 20, 2011 Introduction
This lab was designed to explain the different things osmosis does. Osmosis is the diffusion of water across a semi permeable membrane. Over three days we tested the egg in three different solutions to observe the changes. On Day 1, the main question we answered was what happened to the egg when it was placed in vinegar? Before doing this
I came to my hypothesis was that the vinegar would eat away at the shell and eventually dissolve the shell since it is an acidic solution. Things with acid are corrosive and sometimes poisonous so they eat away at things. On Day 2, the main question we had to answer was what happens to the egg’s mass when it sits in a water or saltwater solution for 30 minutes? I hypothesized that the egg will lose grams because the salt will make the water go outside the cell causing it to shrink. On day 3, the main question we answered was what happens to the egg’s mass when it sits in a syrup solution for 24 hours? I hypothesized that it would gain mass because of how thick the syrup solution was.
: On day we set up our experiment in the first solution which was vinegar. We
had to bring a raw egg to school. My partner ( S.) and I placed both of our eggs in a cup and put our names on the cup. I poured vinegar over our eggs. After that, we placed our cup where the teacher told us to. Day 2
: When we got to class, we got our cups that our eggs were in. We used a spoon to remove the eggs and rinsed it off carefully and dried it with paper towels. We got two cups for each egg and first got the mass of the cup and them the mass of each egg plus the cup. We then determined the mass of the egg alone and recorded the data. I then predicted if I thought the Egg 1 would gain, lose, or stay the same mass after it was placed in a cup of water for 30 minutes. Next, I predicted if I thought the Egg 2 would gain, lose, or stay the same mass after it was placed in a cup of saltwater for 30 minutes.
We then put the water over egg 1 and the saltwater over Egg 2 and waited 30 minutes.
After the 30 minutes was up, we removed the eggs and emptied the solutions. We massed the eggs once again and recorded the data. I predicted what I thought would happen to the eggs if they were placed in pancake syrup for 24 hours. We then covered both eggs in syrup and put them in a safe place. Day 3
: When we got to class we grabbed our cups and carefully removed the syrup from the eggs. We placed a thin disposable tray on the scale and zeroed the scale off. We then placed Egg 1 on the tray and recorded the mass shown. We repeated that step for
Egg 2 and recorded the mass. After we rinsed off everything we used. We got to have fun
with the egg after we finished the lab. We broke both eggs shell (what was remaining) and got to observe the changes in the cytoplasm and nucleus.
After putting the cell in vinegar, we noticed that when we observed it, it was very smelly and soft. We had to be very careful using dealing with it. After putting the cell in water/ saltwater it just looked bigger. It was swollen. After putting the cell in syrup, it looked rotten and like it could bust any minute. Here is the Lab Data Chart
Decalcified egg+ cup
(after being in vinegar)
1.89 g cup
Decalcified egg alone
69.61 g Prediction of mass of egg
(after being in water/
Gain mass, egg swell saltwater) 66 g
Actual mass of egg after 30 72.52 g
minutes in water Prediction of egg mass after Gain
24 hours in pancake syrup
100 g Actual mass of egg after
57.51 g being in syrup 24 hours
When we added water to the egg cell for 30 minutes, the egg gained mass because the cell absorbed the water. When we added pancake syrup to the cell for 24 hours, the egg lost mass. This was because of the sugar in the syrup absorbing the water in the egg causing it to shrink in size. The water didn’t really change in appearance after the 30 minutes was up. The pancake syrup was very thin and had a very bad smell. The syrup was no longer thick as before. This change in appearance was because the sugar absorbed the water out of the cell in the syrup. In every situation water either left or entered the cell causing the mass change. The water and saltwater were a hypotonic environment with respect to the egg cell. This was because water went into the cell. The syrup was a hypertonic environment with respect to the egg cell. This was because the water in the cell left the cell into the solution. Before experimenting with different solutions we had to use vinegar to remove the shell from the egg so the membrane would be soft enough to allow solutions to go in and out of it. A bacterium does not grow well in jellies/ jams
because of all the sugar added. When sugar is added, the water in the cell will be absorbed causing the cells to shrink in size. This means the bacteria cells will shrink and eventually dir because of no water. I think if we placed the eggs in very salty water, it would cause the cells to swell. I predict this because the salt will cause the water to enter the cells making them longer.
This lab really helped us learn more and elaborate on the concept of osmosis. Osmosis is the diffusion of water across a semi permeable membrane. We really saw how the cell was semi permeable because it allowed the water to leave and enter the cell during different situations. This lab was really fun. My question I had to answer on Day 1 was, what happened to the egg cell after it was put in vinegar. My hypothesis was proven correct because the egg cell shell was eaten away at by the acidic vinegar. The shell was really soft. I think if it was in there a little longer that the shell would eventually disappear. My question I had to answer on Day 2 was, what happened to the egg cell’s mass when it was in water/ saltwater for 30 minutes. My hypothesis was proven wrong because I thought the salt would make the water go outside of the cell causing the cell’s mass to shrink. It did completely opposite. The cell’s mass gained. The salt caused the water to go inside the cell which would be a hypotonic environment to the cell.
Hypotonic is when the water goes inside the cell. My question I had to answer on Day 3 was, What happened to the egg cell’s mass after it was placed in pancake syrup for 24 hours. My hypothesis was proven wrong again because I thought the thick solution would cause the egg cell to gain mass. It was opposite again. The sugar in the solution caused the water in the cell to leave the cell and make the cell shrink. This would be a hypertonic environment to the cell. Hypertonic is when the water moves from inside the cell to outside of the cell. The experiment really helps us understand what we are learning in class. And how cells absorb or release water.