Egg-cellent Osmosis Lab

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Annabel Boone
6 years ago
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1 -cellent Osmosis Lab Background: Some chemicals can pass through the cell membrane while others cannot. Not all chemicals are able to pass through a cell membrane with equal ease. The cell membrane determines which chemicals can diffuse into or out of a cell. As chemicals pass into and out of a cell, they move from areas of high concentration to areas of low concentration. Cells in hypertonic solutions have solute concentrations lower than the solution that surrounds them. This concentration difference causes water to move out of the cell into the surrounding solution. Cells in hypotonic solutions have solute concentrations greater than the solution that surrounds them. The concentration difference causes water to move from the solution into the cell. The movement of water into and out of a cell through the cell membrane is called osmosis. Purpose: In this lab, you will use eggs with a dissolved shell as a model for a living cell. You will then predict the results of an experiment that involves the movement of waster through a membrane. Objectives: Model a cell with a cell membrane Predict the direction of diffusion Explain changes that occur in a cell as a result of diffusion. Distinguish between hypertonic and hypotonic solutions. Materials beaker or cup balance safety goggles vinegar (acetic acid) tablespoon or tongs fresh egg paper towels water Procedure: Day 1: 1. Obtain a beaker and label the beaker with your group s initials. 2. Measure the mass of the egg to the nearest 0.1 g and record your measurements both in the space AND table below. CAUTION: When handling raw eggs, clean up any material from broken eggs immediately. Wash your hands with soap and water after handling the eggs. Mass = 3. Put on safety goggles. 4. Place the egg into the beaker and pour enough vinegar to cover the egg completely. It is ok if the egg floats only fill the beaker enough to cover the egg if it didn t float. 5. Store the beaker with the egg in a cool place for 24 hours. 6. Clean up your work area and wash your hands before leaving the

2 Predictions: 1. What do you currently observe when looking at the egg within the beaker with vinegar? 2. What do you think causes the observation that you made? Data Table: Vinegar Mass of Fresh with Shell (Day 1) of with Shell in vinegar (Day 2) after 24 hours in vinegar (Day 2 mass Day 1 mass) x 100 = Day 2 mass Day 2: 1. After 24 hours, observe the egg and record your observations in the above data table. Make sure to include in your observations what you may see today compared to Day 1, 2. Put on your safety goggles. 3. Pour the vinegar from the beakers into a sink. 4. Using a tablespoon or tongs, CAREFULLY remove the eggs and rinse them with water. 5. Place the egg on a paper towel to remove excess liquid. 6. Measure the mass of the egg and record that measurement in the table above. 7. Determine the % change in mass and record in the table above. 8. Return the egg to the beaker. 9. Add syrup to the egg until it is covered. 10. Store the beaker with egg in the same place as before for 24 hours. 11. Clean up your work area and wash your hands with soap and water before leaving the Predictions: 1. Predict how the mass of the egg will change after 24 hours in the syrup. (Hint: An egg is surrounded by a membrane. Inside the membrane, the egg white consists mainly of water and dissolved protein. The yolk consists mainly of fat and water. Syrup is sugar dissolved in water. The protein, fat, and sugar are solutes.)

3 Day 3: 2. What will have occurred if your egg gains mass? If the egg loses mass? 1. After 24 hours, observe the egg and record your observations in the below data table. Make sure to include in your observations what you may see today compared to Day 2, 2. Gently remove your egg from the beaker using the tablespoon or tongs. 3. Gently pat the egg dry with the paper towel. 4. Measure the mass of the egg to the nearest 0.1 g and record your measurements in the table below. 5. Determine the % change in mass and record in the table above. 6. Pour the down the drain and wash the beaker and the spoon with soap and water. 7. Place the egg back into the beaker. 8. Pour enough water into the beaker until the egg is completely covered. 9. Store the beaker with the egg in a cool place for 24 hours. 10. Clean up your work area and wash your hands with soap and water before leaving the Data Table: Corn Syrup Mass of after soaked in vinegar (Day 2) of after soaked in vinegar in (Day 3) after 24 hours in (Day 3 mass Day 2 mass) x 100 = Day 3 mass Predictions: 1. Predict how the mass of the egg will change after 24 hours in the syrup. (Hint: An egg is surrounded by a membrane. Inside the membrane, the egg white consists mainly of water and dissolved protein. The yolk consists mainly of fat and water. Syrup is sugar dissolved in water. The protein, fat, and sugar are solutes.) 2. What will have occurred if your egg gains mass? If the egg loses mass?

4 Day 4: 1. After 24 hours, observe the egg and record your observations in the below data table. Make sure to include in your observations what you may see today compared to Day 3, 2. Gently remove your egg from the beaker with your tablespoon or tongs. 3. Gently pat your egg dry with the paper towel. 4. Find the mass of the egg and record in the below data table. 5. Determine the % change in mass and record in the table above. 6. Obtain a straight pin from your teacher. 7. Carry your egg to sink. While holding your egg over the sink, carefully stick the pin into the egg and remove it. What did you observe? 8. Place the egg into a trash can 9. Pour the water down the drain and wash the beaker and the spoon/tongswith soap and water. Place all clean materials on a drying mat. 10. Clean up your work area and wash your hands with soap and water before leaving the Data Table: Water Mass of after soaked in (Day 3) of after soaked in in water (Day 4) after 24 hours in water (Day 4 mass Day 3 mass) x 100 = Day 4 mass Analysis: 1. What were the percent differences in mass for each test? With shell After Vinegar Vinegar After Syrup Syrup After Water 2. Based on your observations of the change of mass of the eggs in the variant solutions as well as the Background information, determine which solution was the hypertonic versus hypotonic solution. Hypertonic solution: Hypotonic solution:

5 Conclusion: (20 points total) Summarize what happened to the egg over the course of the experiment. (6 points) Summary references the data and percent change in mass. (6 points) Summary references terms uses the words osmosis, hypertonic, and hypotonic solutions. (6 points) Summary accurately illustrates an understanding the behavior of a cell in various solutions using the egg as an example (2 points) The summary correctly uses grammar, punctuation, spelling, and scientific vocabulary.

Problem How does solute concentration affect the movement of water across a biological membrane?

Problem How does solute concentration affect the movement of water across a biological membrane? Name Class Date Observing Osmosis Introduction Osmosis is the diffusion of water across a semipermeable membrane, from an area of high water concentration to an area of low water concentration. Osmosis