Today we will talk about an extension of the experiment of the rubbery egg. In that experiment we soaked an egg in vinegar to make the shell disappear. The shell is removed by the reaction between acetic acid in vinegar and calcium carbonate in the eggshell. Today we will start from this rubbery egg to continue with our experimentation:
You need to soak the rubbery egg in colored water (we had previously added food coloring)
After some hours, this is the amazing result. The eggs have increased in size and have been colored and now we have some bright colored eggs.
Since we wanted to know what had happened inside the eggs, we kept experimenting…We punched a hole in the membrane and watched the water come out like a little fountain.
But what happened to the yolk inside? We dropped the egg to see how it looked like and discovered that nothing had changed in the yolk.
Once the shell has been removed, the egg is only protected by the outer membrane, which is semi-permeable. That meaning it is some kind of filter that allows only the very small molecules (such as water molecules) to go through. This movement of molecules is known as osmosis.
Because of this phenomenon, water goes through the membrane from the zone with the higher concentration of water molecules to the zone with the lowest concentration until both concentrations are equal. As the concentration of colored water is greater than inside the egg (which contains 90% of water), the water molecules (together with the food coloring) move into the egg, making it increase its volume as well as getting colored.
What do you think it will happen with the colored egg if soaked again in a solution saturated with salt or sugar? Will you try it and tell us the results?