When energy is added to liquid water, what do you expect will happen to the water molecules?

• A. The water molecules will move faster and may eventually change to the gas phase.
• B. The water molecules will break apart into hydrogen and oxygen atoms.
• C. The water molecules will remain unchanged regardless of the energy added.
• D. The water molecules will slow down and form a solid.

Answer: (A)

Verified step by step guidance

1. Understand that adding energy to liquid water primarily increases the kinetic energy of the water molecules.
2. Recall that as the kinetic energy of molecules increases, their movement becomes faster and more vigorous.
3. Recognize that if enough energy is added, the water molecules can overcome intermolecular forces holding them in the liquid phase, leading to a phase change from liquid to gas (evaporation or boiling).
4. Note that breaking water molecules into hydrogen and oxygen atoms requires a chemical reaction (like electrolysis), which is not caused simply by adding thermal energy.
5. Conclude that the most direct effect of adding energy to liquid water is increased molecular motion and potentially a phase change to gas, not breaking molecules apart or forming a solid.