Which best describes the behavior of atoms in a solid substance that is melting into a liquid?

• A. Atoms stop vibrating and remain completely stationary.
• B. Atoms form ionic bonds and arrange themselves in a regular lattice.
• C. Atoms lose energy and become more tightly packed together.
• D. Atoms gain enough energy to overcome their fixed positions and begin to move more freely.

Answer: (D)

Verified step by step guidance

1. Understand the physical change occurring during melting: a solid turns into a liquid when it gains enough energy to change its structure and behavior.
2. Recall that in a solid, atoms are tightly packed in fixed positions but still vibrate around those positions due to thermal energy.
3. During melting, atoms absorb heat energy, which increases their kinetic energy and vibrations until they can overcome the forces holding them in fixed positions.
4. As a result, atoms begin to move more freely, breaking the rigid structure of the solid and allowing the substance to flow like a liquid.
5. Therefore, the best description is that atoms gain enough energy to overcome their fixed positions and begin to move more freely.