Name:___________________________________        Hr:____________        Date:___________

Lab: An Egg as a Cell

Purpose:

You will understand and see how diffusion affects a cell membrane

Background Information:

Cells have an outer covering called the cell membrane. The cell membrane controls what moves into and out of the cell. Certain substances needed by the cell move into the cell through the cell membrane. They move by diffusion. The movement of substances from areas where they are in large amounts (high concentration) to areas where they are in small amounts (low concentration) is called diffusion.

Osmosis is a special kind of diffusion involving the movement of water particles. When water moves across a membrane in the same way (from areas of high concentration to areas of low concentration) it is called osmosis.

Materials:

• White vinegar
• Light karo syrup
• Distilled water
• Three 600 ml beakers
• Egg
• Plastic wrap
• Rubber band
• Graduated cylinder

Procedure:

Day #1

1. Label a 600 ml beaker with the word “vinegar.”
2. Pour 200 ml of vinegar from the stock container into the labeled beaker.
3. Carefully place a raw egg into the beaker.
4. Cover the beaker with plastic wrap and secure it with a rubber band. Leave the beaker covered and undisturbed for 2 days.

Day #3

5. After two days, observe any changes in the egg covering and record your results in the data table.
6. Label a second 600 ml beaker with the word “syrup.”
7. Pour 200 ml of syrup from the stock container into the labeled beaker.
8. Carefully remove the egg from vinegar beaker and rinse it with water.
9. Carefully move the egg and place it into the beaker labeled syrup.
10. Cover the beaker with plastic wrap and secure it again with a rubber band. Leave the beaker covered and undisturbed for one day.
11. Measure the amount of vinegar remaining in the first beaker using a graduated cylinder. Record this amount in the data table.
12. Clean out the beaker with soap and water. Dry the beaker and return to the supply tray.

Day #4

13. After 24 hours soaking in syrup, observe any changes in the egg and record your results in the data table.
14. Label a third beaker 600 ml with the word “water.”
15. Pour 200 ml of distilled water from the stock container into the labeled beaker.
16. Carefully remove the egg from the syrup beaker and rinse it with water. Try not to lose any syrup from the beaker.
17. Carefully move the egg and place it into the beaker labeled water.
18. Cover the beaker with plastic wrap and secure it again with a rubber band. Leave the beaker covered and undisturbed from one day.
19. Measure the amount of syrup remaining in the beaker using a graduated cylinder. Record this amount in the data table.
20. Clean out the beaker with soap and water. Dry the beaker and return to the supply tray.

Day #5

21. After 24 hours of soaking in water, observe any changes in the egg and record your results in the data table.
22. Measure the amount of water remaining in the beaker using the graduated cylinder. Record this amount in the data table.
23. Clean out the beaker with soap and water. Dry the beaker and return to the supply tray.

Hypothesis:

Hypothesis egg in vinegar:

Hypothesis egg in syrup:

Hypothesis egg in water:

Data Table:

Questions:

1. The movement of a substance from where it is in large amounts to where is is found in small amounts is called:

2. Water diffuses across a membrane by a process called:

3. Vinegar is made of a weak acid called acetic acid. What happened to the shell of the egg when you placed it in vinegar?

4. When the egg was placed in the vinegar which way did the water molecules in the vinegar move? (into or out of the cell)

5. How did you know? Sketch the egg before and after soaking the egg in the vinegar solution. Use arrow to show the direction of how the water molecules moved.

6. How can you explain the amount of liquid remaining when the egg was removed from the syrup? Hint: Use the word diffusion in your answer.

7. When the egg was placed in the syrup after being removed from the beaker of vinegar solution, which way did the water molecules move? (into or out of the cell)

8. How did you know? Sketch the egg before and after soaking the egg in the syrup solution. Use arrows to show the direction of how the water molecules moved.

9. Give an example of diffusion in everyday life.