Question

A.
B.
C.
D.
3. Which of the following statements about physical and chemical
changes is TRUE?
Only physical changes alter the molecular structure of a substance.
Only chemical changes alter the molecular structure of a substance.
Both physical and chemical changes alter the molecular structure of
a substance.
Neither physical nor chemical changes alter the molecular structure
of a substance.

Answer 1

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.