Egg Diffusion Experiment
Background
Some chemicals can pass through the cell membrane, but others cannot. The cell membrane determines which chemicals can diffuse into or out of a cell. The cell membrane is selectively permeable or semipermeable.
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 concentrations of dissolved chemicals (solute) lower than the solution that bathes them. This concentration difference causes water to move out of the cell into the solution. Cells in hypotonic solutions have solute concentrations greater than the solution that bathes them. This 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.
In this lab, you will use eggs with a dissolved shell as a model for a living cell. You will predict the results of an experiment that involves the movement of water through a membrane.
Objectives
· Explain the changes that occur in an egg as a result of diffusion.
· Use that information to describe how cell membranes are semipermeable.
Materials
· Mason jar with lids
· fresh egg
· Masking tape
· marker
· vinegar
· string
· ruler
· triple beam balance
· deionized water
· corn syrup (Karo syrup)
· Food coloring
Procedure
Preparation:
1. Place one fresh, raw egg into a mason jar.
2. Pour enough vinegar in the cup or jar to cover the eggs. Cover the jar with the lid
3. Using a marker, write your group’s name and period on a piece of masking tape and label your jar.
4. Allow the eggs to soak for 24-48 hours or until the shells are completely dissolved.
Initial Measurements:
5. Carefully rinse your egg and rub off any excess eggshell. Empty the vinegar in your jar into the sink.
6. Record your qualitative (descriptive) data/observations for Day 1 and Day 2 on your lab worksheet.
7. CAREFULLY measure the circumference of the egg by wrapping a string around the biggest part of the egg and measuring the string with a ruler. RECORD your initial measurements in TABLE 1.
8. Find the mass of your egg using the triple beam balance. Measure the mass of the egg with the jar. Then measure the mass of the jar. You must subtract the mass of the jar from the mass of the egg with the jar to get the mass of the egg.
(Mass of egg with jar) – (Mass of jar) = Mass of Egg
Record your data in TABLE 2.
Soaking in Deionized Water or Corn Syrup:
9. When you are done measuring your egg and jar, place the egg back into the jar.
10. Half the class will add the label “WATER” to their jar and the other half will label it “SYRUP.” Be sure to also write your group’s name and period.
11. Pour enough deionized water with food coloring or corn syrup in your beaker to cover the egg. Securely close the lid on your jar.
12. Allow the eggs to soak for at least 24 hours.
Final Measurements:
1. Take your egg out of your jar carefully. Rinse your jar and set it upside down to dry on paper towels.
2. Measure the circumference (widest part) of the eggs and record in TABLE 1.
3. Don’t forget to record your qualitative data. You may draw pictures to illustrate what happened to the eggs.
4. Find the mass of your egg on the triple beam balance and record your data in TABLE 2.
5. Calculate the difference in size (TABLE 1) and mass (TABLE 2) for each egg.
6. Carefully dispose of your egg.
Egg Diffusion Experiment DATA SHEET
Name: ______Date: ______Period: ____
Observations
Preparation:
Date:
Egg name:
Egg Appearance:
Initial Measurements:
Date:
Egg Appearance:
Soaking in Deionized Water or Corn Syrup:
Date:
Egg Appearance:
Liquid Egg was soaked in:
Final Measurements:
Date:
Egg Appearance:
TABLE 1. Circumference of eggs soaked in two liquids
Group Names / Liquid / Initial Circumference (cm) / Final Circumference (cm) / Size Difference (final-initial)TABLE 2. Mass of eggs soaked in two liquids
Group Names / Liquid / Initial Mass (g) / Final Mass (g) / Mass Difference (final-initial)Questions
1. What is a hypertonic solution? What egg was in a hypertonic solution?
2. What is a hypotonic solution? What egg was in a hypotonic solution?
3. What would happen to the egg if it were placed in an isotonic solution? Explain.
4. An egg membrane is a type of cell membrane. How are cell membranes semipermeable?