Final answer:
Boiling water, a pencil being sharpened, and freezing water are all examples of physical changes, as they involve changes in state or form without altering the chemical composition of the substance.
Step-by-step explanation:
Physical changes in matter refer to changes in the state or form of a substance without altering its chemical composition. Among the options given:
- a. Boiling water is a physical change, as it converts water from its liquid state (H₂O (l)) to its gaseous state (H₂O (g)) without changing its chemical structure.
- b. A pencil being sharpened is also a physical change because it involves altering the shape of the pencil but not its chemical composition.
- d. Freezing water is a physical change, as it involves water going from a liquid to a solid state, but the molecular structure of H₂O remains the same.
On the other hand, exploding dynamite and rotting cheese are examples of chemical changes because they involve chemical reactions that result in new substances being formed.