Transport Across a Membrane Lab
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| Name: | ________________________________ |
Date: | ___________ |
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| Teacher: | ________________________________ |
Period: | ___________ |
Lab #: _______
Aim
To determine how and under what circumstances materials will transport across the membrane of an egg.
Materials
raw egg, vinegar, Karo syrup, distilled water, three 250 mL beakers, two graduated cylinders, an overflow can, a spoon, a marker, and three pieces of aluminum foil
Overview
Depending upon the concentration of water in an egg and that in its surrounding environment, water may diffuse into or out of the egg. The egg will be placed into three different solutions, each with a different concentration of water, to illustrate this effect.
Procedure
- Fill the overflow can with enough water so that the egg will be completely submerged when placed in the can. Measure the amount of water in the can, then place the egg into the can and measure the new height of the water. The difference in these two measurements is the egg's volume. Record this value in the table below.
- Using the graduated cylinder, measure 100 mL of vinegar. Pour this vinegar into a beaker and lable the beaker "Vinegar".
- Place the egg into the "Vinegar" beaker. Cover the top of the beaker with a piece of aluminum foil. Fold the aluminum foil down along the sides of the beaker so that it cannot fall off easily.
- Allow the "Vinegar" beaker to sit for two days.
- After two days, use the spoon to remove the egg and determine its volume using the same procedure as in step #1. Also, pour the contents of the beaker into the graduated cylinder to determine the volume of vinegar remaining. Record these measurements in the table. Also note any qualitative changes (in color, texture, etc.) which occured in the egg.
- Using the graduated cylinder, measure 100 mL of Karo syrup. Add water to teh graduated cylinder until the solution reaches 150mL. Pour this sugar solution into another beaker and lable the beaker "Sugar solution".
- Place the egg into the "Sugar solution" beaker. As in step #3, cover the top of the beaker with a piece of aluminum foil and fold it down along the sides so that it cannot fall off.
- Allow the "Sugar solution" beaker to sit for one day.
- After one day, remove the egg using the spoon and measure its volume. Also measure the volume of sugar solution remaining in the beaker by using the graduated cylinder. Record these values in the table. Make a note of any qualitative changes which you observe.
- Use the graduated cylinder to measure 150 mL of distilled water. Pour this into the third beaker and label it "Distilled water".
- Place the egg into the "Distilled water" beaker. As before, cover the beaker with a piece of aluminum foil and fold it down along the sides.
- Allow the "Distilled water" beaker to sit for one day.
- After one day, use the spoon to remove the egg. Measure the eggs volume using the overflow can, and measure the volume of distilled water remaining in the beaker. Record these measurements in the table. Write down any qualitative changes in the egg.
Observations
Record the data you gathered on the first and second day in the table below.
| Movement through the egg shell |
| | Volume before | Volume after | Change in volume |
| egg initially | | | |
| vinegar | 100 mL | | |
| egg after vinegar | | | |
| sugar solution | 150 mL | | |
| egg after sugar solution | | | |
| distilled water | 150 mL | | |
| egg after distilled water | | | |
In the space below, record any qualitative changes you noticed in the egg.
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Definitions of terms
In answering the questions and writing your conclusions, you may wish to use the following terms to make your answer complete.
- diffusion - the movement of molecules from an area of high concentration to an area of low concentration
- osmosis - the diffusion of water
- plasmolysis - a type of osmosis in which water moves out of the material
- deplasmolysis - a type of osmosis in which water moves into the material
- isotonic solution - a solution with equal concentration of solute inside and outside of the material
- hypertonic solution - a solution with more solute in the surrounding environment than in the material
- hypotonic solution - a solution with less solute in the surrounding environment than in the material
Questions
- What was the purpose of covering the beakers with aluminum foil?
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- The movement of water from an area of high concentration to an area of low concentration is called ________________
- At which points did water flow into the egg? How can you tell?
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- At which points did water flow out of the egg? How do you know?
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- Which solutions (if any) were hypertonic, isotonic, or hypotonic? Explain how you know.
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Conclusions
In the space below, write down any conclusions you can draw from this experiment. You may wish to explain how the data you gathered relates to the qualitative changes you observed in the eggs. You can also discuss some of the implications of your findings; for instance, why fruits and vegetables are sprayed with water at a market.
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Sources of Error
Identify any possible sources of error which may have affected the results of this experiment.
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