On a clear, sunny winter day with an outside temperature of -10ºC, you hang your freshly laundered clothes outside. In the afternoon, the clothes dry completely after initially freezing. What change of state has occurred in the water?

On a clear, sunny winter day where the outside temperature is -10ºC, hanging freshly laundered clothes outside leads to a phenomenon called sublimation. This process involves the conversion of water from its solid state (ice) directly into a gaseous state (water vapor) without passing through the liquid phase.

Initially, when the clothes are hung outside, the moisture in them freezes due to the low temperatures. However, as the sun shines, the energy from the sunlight can provide enough heat for the ice to change directly into water vapor, allowing the clothes to dry even in sub-zero temperatures. This indicates that the water molecules are gaining energy enough to escape into the atmosphere as vapor, showcasing sublimation.

Cooling, condensation, and melting do not accurately describe the process occurring here. Cooling would indicate a temperature drop without a phase change, condensation involves the transition from gas to liquid, and melting refers to the change from solid to liquid, which does not occur in this scenario. Thus, the correct answer highlights the unique ability of ice to transform directly into vapor under the right conditions, even in cold temperatures.