Name ________________

Period:________________

Egg Lab

Selectively Permeable Membranes

 

Purpose:  The purpose of this lab is to investigate the properties of a selective permeable membrane.

 

Materials:

Two 250 ml beakers, corn syrup, vinegar, balance, paper towels, eggs, plastic wrap, water.

 

Procedure:

Day 1: Weigh and determine the volume (by water displacement) of two eggs.  Use a calculator to determine their densities (mass divided by volume. Label two 250 ml beakers with the initials of everyone in your lab group.  Label one of the beakers “Egg 1” and the other “Egg 2”.  Place one egg into each beaker. Cover each egg with vinegar (3% acetic acid).  Continue filling the beakers until the level of the vinegar is about a half inch above the top of the eggs.  Make observations about the appearance of the eggs.  Then cover the beakers with cling wrap and set them aside as directed by your teacher.

 

Day 2:  Remove the cling wrap from the beaker.  Flood the beakers with water to remove the vinegar.  Carefully remove the eggs from the beakers and gently rinse them off.  Place them each on a piece of paper towel, keeping track of which is egg 1 and which is egg2.  Record your observations.  Weigh and determine the volume of each egg again.  Calculate their densities.  Rinse out the two beakers and put the eggs back in (keeping track which is which).  Carefully fill the beaker labeled “Egg 1” with tap water to a half inch above the egg.  Carefully fill the beaker labeled “Egg 2” with corn syrup to a half inch above the egg.  Then cover the beakers with cling wrap and set them aside as directed by your teacher.

 

Day 3:  Remove the cling wrap. Remove Egg 1 and put it on a paper towel. Carefully flood the beaker labeled “Egg 2” to rinse off the corn syrup.  Record your observations of the two eggs.  Weigh and determine the volumes of each egg again.  Calculate their densities.  Discard the eggs and clean up as directed by your teacher.

 

Data:

 

Day 1: Raw, unspoiled eggs, straight from the refrigerator.

 

 

Mass (grams)

Volume (ml)

Density (g/ml)

Egg 1

 

 

 

Egg 2

 

 

 

 

Observations of the eggs in the vinegar:

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Chemical reaction:  HC2H3O2 + CaCO3 Þ Ca(OH)2 + CO2 + H2O

 

Day 2: Same eggs after being soaked in vinegar for 24 hrs.

 

Observations of “vinegarized” eggs:

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Mass (grams)

Volume (ml)

Density (g/ml)

Egg 1

 

 

 

Egg 2

 

 

 

 

 

Day 3:

 

Observations:

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Egg 1 (soaked in tap water):

 

Egg 2 (soaked in corn syrup):

 

 

Mass (grams)

Volume (ml)

Density (g/ml)

Egg 1

 

 

 

Egg 2

 

 

 

 

 

 

 

 

 

Questions:

 

 

 

1.         What did the vinegar do to the eggshell?

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2.         Label the drawings below, showing what happened to the two eggs between day two and day three.  In the drawings titled “before”, label the tap water and the corn syrup, and use dots to show relative concentrations in the water, eggs and corn syrup.  Also draw arrows showing the direction of the movement of water into or out of the eggs.  Then in the drawings labeled “after”, draw the eggs’ final sizes and appearances.

 

 


Before:

 

 

 

Egg 1

 

Egg 2

 
 

 

 

 

 

 

 

 

 

 


After:

 

 

 

 

 

 

 

 

 

 

 

Egg 1

 

Egg 2

 
 

 

 

 


3.                  Define the following terms:

a.       Diffusion

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b.      Osmosis

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4.                  In which situation was the egg in a

a.       hypertonic solution

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b.      hypotonic solution

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5.                  Compare the densities of the eggs in each step of the lab.

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6.                  To be selectively permeable means to let some substances through but not others.  Which part of this lab demonstrated that the egg’s membranes were selectively permeable? Why?

 

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Conclusion:

 

In your own words, sum up this lab.  What happened and what did it demonstrate?