Which of the following best explains why a solid changes to a liquid when heat is added?

• A. The added heat converts the solid directly into a gas without passing through the liquid phase.
• B. The added heat causes the particles to lose energy and move closer together.
• C. The added heat decreases the temperature of the solid, causing it to melt.
• D. The added heat increases the kinetic energy of the particles, allowing them to overcome the forces holding them in fixed positions.

Answer: (D)

Verified step by step guidance

1. Understand that a solid has particles arranged in a fixed, orderly structure with strong intermolecular forces holding them in place.
2. Recognize that adding heat to a solid increases the kinetic energy of its particles, making them vibrate more vigorously.
3. When the kinetic energy becomes sufficient to overcome the intermolecular forces, the particles can move past each other, leading to a phase change from solid to liquid.
4. Note that this process is called melting, and it occurs at a specific temperature known as the melting point.
5. Therefore, the best explanation is that the added heat increases the kinetic energy of the particles, allowing them to overcome the forces holding them in fixed positions.