Final answer:
Liquid water at 0°C does have to give up energy, known as the heat of fusion, to become ice at 0°C. This process is exothermic and involves energy being released as the water molecules transition to a solid state.
Step-by-step explanation:
The statement that liquid water at 0°C must give up energy to become ice at 0°C is true. When water freezes, the molecules slow down and arrange into a crystalline structure. This process requires the release of energy known as the heat of fusion. Each molecule in the liquid phase has more thermal energy than in the solid phase at the same temperature because of the kinetic energy associated with their movement. As the water turns into ice, it gives up this energy to the environment.
Freezing, like condensation, is an exothermic process, meaning it releases energy. This is in contrast to melting or vaporizing, which are endothermic processes and require an input of energy to overcome molecular attraction. The temperature of a substance does not change during a phase change until the entire phase change is complete. Therefore, the energy transfer during the freezing process does not result in a temperature change but rather in a change of state from liquid to solid.