Question

Why is the boiling of eggs a chemical change, while the boiling of water is a physical change?

Answer 1

Part 1: Boiling of eggs, a chemical change:

• While cooking, Food materials undergo chemical changes. The cooked food cannot be converted back into its original form. For example, cooked vegetables cannot be changed into raw vegetables, etc.
• The chemical composition of a boiled egg is different from that of a raw egg. Heat causes denaturation of protein chains, converting egg into a solid mass which can not be converted back into its solid form. Therefore, it is a type of chemical change.

Part 2: Boiling of water, physical change:

• Boiling of water is a physical and a reversible change.
• No new chemical compound is formed during boiling of water.
• By lowering the temperature, water vapor can be condensed back into liquid water.