During boiling, what happens to water molecules?

• A. During boiling, water molecules move faster and move farther apart as they absorb heat.
• B. They move faster and remain close together as they absorb heat.
• C. They move more slowly but move farther apart as they lose heat.
• D. They move faster and move farther apart as they lose heat.

Answer: (A)

When water boils, heat energy increases the kinetic energy of the water molecules, so they move faster. That added energy also makes the molecules push apart more as they transition from liquid to vapor, causing the liquid to expand and form bubbles that rise to the surface. So the idea that water molecules move faster and move farther apart as they absorb heat is what happens during boiling. If the molecules were getting faster but staying close together, or if they were losing heat and slowing down, that would not describe boiling.