Question

A student hangs wet clothes outdoors on a winter day when the temperature is \(-15^{\circ} \mathrm{C}\). After a few hours, the clothes are found to be fairly dry. Describe the phase changes in this drying process.

Short answer

The clothes initially wet with water when put outside in the winter goes through two phase changes. First, the water turns into ice due to freezing because of the cold temperature. Then, the ice sublimates directly into water vapor, skipping the liquid phase again. After some time, all water on the clothes has sublimated, leaving them dry.

Step-by-step solution

Initial State

The clothes are initially wet. This means they are covered in liquid water.

Change of phases

When the clothes are hung outside in the cold temperature, the water on them undergoes two phases changes. The first phase change is from the liquid state to the solid state, more commonly known as freezing. This happens because the temperature outside is below the freezing point of water (0 degrees Celsius). The water on the clothes turns into ice.

Sublimation

The second phase change is directly from the solid state to the gas state, skipping the liquid state. This is called sublimation. This occurs because even in sub-zero temperatures, ice is capable of sublimation given enough time. The ice(sublimated water) from the clothes turns into water vapor and dissipates into the air.

Result

After some time, most, if not all, of the water on the clothes has sublimated, leaving the clothes dry.