Wednesday, April 30, 2008


Home Science Tools

The Case of the Disappearing Eggshell

An egg is covered by a hard shell to help protect the chick growing inside. When the chick is ready to hatch, it breaks the shell open. Try this experiment to find out what a shell is made of:

What You Will Need:

An egg from the grocery store
A drinking glass
White vinegar
What To Do:

Set a raw egg in a glass of white vinegar so that it's completely covered in the liquid. Bubbles should start to form on the surface of the egg.

Let the egg sit in the vinegar for about 3 days and then take it out and rinse it in water, being careful not to pop it. Does it feel different from when you put it in the vinegar? Does it still have a white shell?

What's Happening?

The eggshell disappeared! But there might be some chalky white stuff left on the egg. This is because vinegar is a type of acid that "ate" away and dissolved the calcium carbonate that the shell is made out of. (Chalk is also made out of calcium carbonate!) When something dissolves, it breaks into very tiny pieces and mixes with a liquid. You can see it happening if you put a sugar cube into a cup of hot water and stir. The sugar cube disappears as the sugar dissolves into the water.

You might be wondering why the egg white and yolk inside the shell stayed in the shape of an egg even though the shell is gone. This is because the egg has another covering underneath the shell; called a membrane. It is very thin and you can see the yellow yolk through it. The vinegar can't dissolve the egg membrane, but some of it was able to get through the membrane, making the egg swell up.

Shrinking Egg

In the last project, the egg membrane let liquid in, making the egg swell a little bit. Do this project to see if you can get the egg to shrink!

What You Will Need:

The egg without its shell from the previous project
A drinking glass
Corn syrup
What To Do:
Carefully place the egg in a glass of corn syrup, so the egg is covered.
Let the egg sit in the corn syrup for about 3 days. Then take it out and see what happened!

What's Happening?

The egg shrank! This is because the egg membrane let a bunch of water pass out of the egg to try to balance how much water was inside the egg and how much water was outside it in the glass. The very tiny parts that make up corn syrup (called molecules) were still too big to pass through the membrane, so none of the corn syrup got inside the egg. The egg lost a lot of water, but didn't get anything to take the water's place, so it looks a little funny! Do you think it would fill up again if you put it in a glass of water? Try it out!

The fact that the egg membrane can let some things through is very important for a baby chick. Air passes through the membrane, just like water did in this experiment, and that allows the baby chick to breathe while it's inside the egg.

Marcus Garvey School of Thought