Disappearing egg shell

from Douglass Middle Academy

How can you seen inside an egg without cracking the shell? Here is a cool way to remove the outer shell from an egg (but not is you want to use the egg afterward …)

What you need

• A clear jar with a wide enough mouth to fit the egg inside

• A lid for the jar

• A raw egg

• Clear vinegar

                                                                                                                                        courtesy of aeb.org

What to do

Adult supervision is recommended. Note the size of the egg before you begin. Carefully place the egg in the jar and fill with enough vinegar to completely cover the egg. Bubbles form immediately on the surface of the egg. Cover the jar and allow it to react for three days. Watch how the number of bubbles on the surface of the egg changes and how the appearance of the egg changes. After three days the entire shell should be gone and the shape and size of the egg changed.

What is happening

The outer shell of the egg is made of calcium carbonate, also known as limestone. Vinegar reacts with calcium carbonate to produce carbon dioxide, which is the gas in the bubbles that form on the surface of the egg. As the vinegar dissolves the outer shell, the cell membrane, the rubbery layer that surrounds the insides of the egg, is exposed. This layer does not react with vinegar and it is because of the presence of this layer that the yolk and egg white do not spill out when the outer shell is removed. The cell membrane is semi-permeable, which means that some of the water in the vinegar is able to seep through the layer into the inside of the egg. Water always moves from the side of the membrane with fewer materials present to the side with more present. Since there are more particles present within the egg, the water moves inside the membrane. The particles in the egg white and yolk are too large to move through the membrane and remain inside. This is why the egg expands after the outer shell is removed and why the membrane is semi-permeable – only certain particles are able to move through.

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