Does liquid water at 273 K (0ºC) have to lose energy to become ice at the same temperature?

When liquid water at 273 K (which is 0ºC) is transitioning into ice, it must lose energy in the form of latent heat. The process of freezing involves a change in phase from liquid to solid. Even at 0ºC, water molecules in the liquid state have enough energy to move freely, but as they lose energy, they slow down and begin to form solid structures, eventually becoming ice.

This energy loss occurs because the molecules need to release heat energy to facilitate the formation of the hydrogen bonds that hold the water molecules in a solid ice structure. Therefore, at 0ºC, while the temperature remains constant, energy is still being released during the phase change from liquid to solid.

Maintaining the temperature at 273 K while transitioning from water to ice confirms that energy must indeed be lost in the form of latent heat for the phase change to occur.