When heat is added to water, what happens to the water molecules?

• A. The molecules remain stationary and do not change.
• B. The molecules slow down and form a solid.
• C. The molecules lose energy and condense into a liquid.
• D. The molecules move faster and may eventually change from liquid to gas.

Answer: (D)

Verified step by step guidance

1. Understand that when heat is added to water, energy is transferred to the water molecules, increasing their kinetic energy.
2. Recall that kinetic energy is related to the motion of molecules; as kinetic energy increases, molecules move faster.
3. Recognize that faster-moving molecules can overcome intermolecular forces holding them in the liquid state, leading to a phase change from liquid to gas (evaporation or boiling).
4. Note that the process of molecules moving faster and changing phase is a physical change, not a chemical change.
5. Conclude that adding heat causes water molecules to move faster and can eventually cause the water to vaporize, changing from liquid to gas.