Fat Egg, Skinny Egg-Learning about Osmosis

What is Osmosis?

 The moving of water across a semi-permeable  membrane, from an area of high concentration (where there are a lot molecules) to an area of low concentration (where there are less molecules).

First you need to perform the classic Naked Egg Experiment.

You will need:

• 2 bowls
• 2 eggs without cracks
• distilled white vinegar        

 Procedure:

1. Place each egg into a bowl.
2. Cover each egg completely with vinegar.
3. Let the eggs stand in vinegar for 24 hours.
4. Gently rinse off eggs in clean water.

Things to notice and record:

• How egg looks and feels with its egg shell?
• How egg looks and feels without its shell?

Observing Osmosis

You will need:

• 2 bowls
• water
• 2 Tbsp salt
• 1/2 cup corn syrup

Procedure:

1. Place each well rinsed egg into a bowl.
2. Fill each bowl with water, covering each egg.
3. In one bowl add 2 Tbsp salt to the bowl.
4. In the other bowl add 1/2 cup corn syrup to the bowl.
5. Observe the eggs for the next 24 hours. 

Things to notice and record?

• Which egg became larger? smaller?
• Which egg show that material can move into a cell?
• Which egg shows that material can move out of a cell?

Words to look up and define:

1. semi-permeable membrane
2. membrane
3. hypotonic solution
4. hypertonic solution

Edible diagram to explain hypertonic and hypotonic solutions:

Hypotonic solution:  There are fewer molecules M&M's on the outside of the cell than on the inside.

Use 20 M&M's (which represent molecules), a plastic lid (to represent the egg in our experiment), and a piece of paper (represents the water solution).  Place the plastic lid on top of the piece of paper.   Place  14 molecule M&M's inside the "egg".  Put 6 M&M's  on the outside of the egg.  Which has more molecules?  
The water solution and the egg want to have the same number of molecules.  Or said another way, they want to be in"equilibrium".   Move the M&M's until you have the same number of M&M's inside the egg as outside of the egg.  

Hypertonic solution: There are more molecule M&M's on the outside of the cell than on the inside.

Place 14 molecule M&M's outside of the "egg".  Put 6 molecule M&M's inside the egg.  Which has more molecules? Remember that they want to have the same number of molecules M&M's.  Move the M&M's so that you have the same number in the cell as outside the cell.  

Notes from Mom:

• Naked Egg experiment with more explanation
• Biology Junction
• When recording your observations, you can add taking weights of eggs before and after being in their solutions.

SALT

CORN SYRUP