Which of the following is greater in magnitude for water: the heat of fusion or the heat of vaporization?

• A. Neither; both are zero
• B. The heat of fusion
• C. The heat of vaporization
• D. Both are equal

Answer: (C)

Verified step by step guidance

1. Understand the definitions: The heat of fusion is the amount of energy required to change a substance from solid to liquid at its melting point, while the heat of vaporization is the energy required to change a substance from liquid to gas at its boiling point.
2. Recall that both processes involve breaking intermolecular forces, but vaporization requires breaking these forces completely to transition into the gas phase, which generally requires more energy than just loosening them to transition into the liquid phase.
3. Recognize that for water, the heat of vaporization is significantly larger than the heat of fusion because vaporization involves overcoming stronger intermolecular attractions (like hydrogen bonding) to separate molecules completely.
4. Express the relationship conceptually: \(\Delta H_{\text{vap}} > \Delta H_{\text{fus}}\) for water, where \(\Delta H_{\text{vap}}\) is the heat of vaporization and \(\Delta H_{\text{fus}}\) is the heat of fusion.
5. Conclude that the heat of vaporization is greater in magnitude than the heat of fusion for water, which aligns with the physical understanding of phase changes and energy requirements.