When water changes from a liquid to a solid, how does the motion of its molecules change?

• A. The molecules move more rapidly and spread farther apart.
• B. The molecules move at the same speed but change direction more frequently.
• C. The molecules stop moving completely.
• D. The molecules move more slowly and become fixed in place.

Answer: (D)

Verified step by step guidance

1. Understand the states of matter: In a liquid, molecules have more freedom to move around, while in a solid, molecules are more tightly packed and have limited movement.
2. Recall that temperature affects molecular motion: When water freezes, its temperature decreases, causing the molecules to lose kinetic energy and move more slowly.
3. Recognize that in the solid state (ice), water molecules are arranged in a fixed, orderly structure (a crystal lattice), which restricts their movement to vibrations around fixed positions rather than free movement.
4. Contrast this with the liquid state, where molecules can slide past each other and move more freely, resulting in faster and less restricted motion.
5. Conclude that when water changes from liquid to solid, the molecular motion decreases in speed and becomes restricted to fixed positions, meaning molecules move more slowly and become fixed in place.