Is cooking an egg an example of a physical or chemical change? Explain your answer.
The Correct Answer and Explanation is:
Answer: Cooking an egg is an example of a chemical change.
Explanation:
When an egg is cooked, it undergoes a chemical change because the heat causes permanent changes in the egg’s molecular structure. The egg white and yolk contain proteins that are originally in a folded, globular shape. When heat is applied during cooking, these proteins unfold in a process called denaturation. Once unfolded, the protein molecules form new bonds with one another, resulting in a firm, solid structure. This transformation is not reversible under normal conditions, which is one of the key characteristics of a chemical change.
In a raw egg, the egg white (also called albumen) is mostly water and contains dissolved proteins such as ovalbumin. These proteins are soluble in water and give the raw egg white its clear, jelly-like appearance. Upon heating, the proteins lose their natural structure and coagulate, changing the egg white from clear to opaque and from liquid to solid. The same process happens in the yolk, which also contains fats and proteins that undergo chemical changes.
This change is fundamentally different from a physical change, such as melting ice or breaking a glass, where the substance maintains its original chemical composition. In the case of cooking an egg, the original proteins cannot be restored to their raw state. Additionally, there is often the release of gas and changes in smell, which are further indications of a chemical reaction taking place.
Therefore, cooking an egg involves the breaking of old chemical bonds and the formation of new ones, producing new substances with different properties from the original raw egg. This makes it a clear example of a chemical change.
