* Protein Denaturation: The heat from boiling disrupts the delicate bonds holding the protein molecules in the egg white and yolk together. This causes the proteins to unfold and change shape, a process called denaturation.
* New Bonds Formation: As the proteins unfold, they can then form new bonds with other proteins. This creates a new, more rigid structure that results in the solid, cooked egg.
* Color Change: The yolk turns yellow due to the denaturation of proteins and the breakdown of carotenoids, pigments responsible for the egg's color.
* Irreversibility: You can't simply cool down a cooked egg to get the liquid white and yolk back. The changes in the protein structure are permanent.
In contrast, physical changes involve only a change in form or appearance, not in chemical composition. For example, freezing water is a physical change, as the water molecules remain the same, only their arrangement changes.
In summary, boiling an egg involves a change in the chemical composition of the proteins within the egg, making it a chemical change.
