The correct statement about physical and chemical changes is:
Both physical and chemical changes alter the molecular structure of a substance.
- Physical changes involve changes in the physical properties of a substance, such as changes in shape, size, or state (solid, liquid, gas), without altering the chemical composition of the substance. For example, melting ice into water is a physical change because the water molecules remain the same.
- Chemical changes, on the other hand, involve the formation of new substances with different chemical properties. In a chemical change, the molecular structure of the substances involved is altered. For instance, burning wood to produce ash is a chemical change as the wood undergoes a chemical reaction to form different substances like carbon dioxide and water vapor.
Therefore, the statement that only physical changes or only chemical changes alter the molecular structure of a substance is incorrect. The correct statement is that both physical and chemical changes can alter the molecular structure of a substance.
