Observations and results
Did all of the eggs have at least a few small blue dots on the inside of their shells? Were the dots mostly clustered in one or a few areas on the inside of each shell?
Directly under the chicken egg's shell are two membranes. When the eggs are laid by the mother they are warmer than the air, and as they cool the material inside the egg shrinks a little bit. This shrinkage is what pulls the two membranes apart, leaving behind the small air sack that is filled with oxygen. As the developing chick grows it uses the oxygen from the air sack and replaces it with carbon dioxide. The tiny pores in the shell allow the carbon dioxide to escape and fresh air to get in. The chicken egg has more than 7,000 pores in its shell to allow this to happen! These pores also allow water to go through the shell, which is why the dye appears as small dots on the inside of the shell, often clustered in certain areas, and why an egg after being hard-boiled would weigh slightly more than when it was raw. Also, freshly laid eggs do not allow water to penetrate as well as older, commercial eggs do, so fewer blue spots will probably be visible on the inside of fresher eggs compared with older ones.
Dispose of the raw eggs by pouring them down the drain. (The eggs should not be eaten because they were soaked with dishwater detergent.) Thoroughly clean any surface the raw eggs touched because they can carry salmonella.
More to explore
Respiratory System: Oxygen Delivery System from The Franklin Institute
Your Lungs & Respiratory System from KidsHealth
The Parts of the Egg from 4-H Virtual Farm
How Does a Chick Breathe Inside Its Shell? from Science Buddies
This activity brought to you in partnership with Science Buddies