What makes food coloring stick to the egg shell of a hard boiled egg?

Food coloring sticks to the eggshell of a hard-boiled egg due to a process called absorption. Here's a detailed explanation of what happens:

1. Egg Shell Porosity: The eggshell is composed of calcium carbonate, which is a porous material. When you immerse a hard-boiled egg in food coloring, the pores of the eggshell absorb the dye molecules.

2. Chemical Reactions: The food coloring contains dyes, which are organic molecules. These molecules can interact with the calcium ions present in the eggshell through chemical bonding. The dye molecules form bonds with the calcium ions, causing the color to adhere to the eggshell.

3. Adhesion: Once the dye molecules are chemically bonded to the calcium ions, they are effectively "stuck" to the eggshell. This adhesion is what prevents the food coloring from easily washing off the eggshell when you rinse the egg.

4. Intermolecular Forces: In addition to chemical bonding, intermolecular forces also contribute to the adhesion of food coloring to the eggshell. Intermolecular forces include van der Waals forces and hydrogen bonding. These forces create an attractive interaction between the dye molecules and the eggshell surface, further enhancing the adhesion of the food coloring.

By combining chemical reactions and intermolecular forces, the food coloring is able to successfully stick to the eggshell of a hard-boiled egg, resulting in the vibrant colors that are commonly associated with decorated Easter eggs.