Question

When wet laundry is hung on a clothesline on a cold winter day, it will freeze but eventually dry. Explain.

Short answer

Wet laundry hung on a clothesline on a cold winter day eventually dries due to the process of sublimation, where the ice formed in the fabric turns directly into water vapor without passing through the liquid state, as well as evaporation if the temperature rises or residual liquid water is present.

Step-by-step solution

Understand the initial state of the wet laundry

The wet laundry is initially saturated with water, which means that it contains a significant amount of liquid water absorbed in the fabric.

Discuss the freezing of water in the laundry

On a cold winter day, the temperature is likely to be below the freezing point of water (0°C or 32°F). When the wet laundry is hung on a clothesline, the liquid water in the fabric will freeze and turn into ice crystals.

Introduce the concept of sublimation

Sublimation is the process through which a substance transitions from a solid state (in this case, ice) directly to a gaseous state (water vapor) without passing through the liquid state. This process occurs when the air is dry, allowing the ice to absorb energy from the surrounding environment and turn into water vapor.

Discuss the role of sublimation in drying the laundry

As sublimation takes place, the ice crystals in the frozen laundry turn into water vapor. This effectively removes water from the laundry, slowly drying it out despite the cold temperature. This process continues until most of the water in the laundry has transitioned from the solid state (ice) to the gaseous state (water vapor), leaving the laundry dry.

Mention the role of evaporation—if applicable

If the temperature increases slightly during the day or if there is any liquid water remaining in the laundry, evaporation can also contribute to the drying process. Evaporation is the process where liquid water turns into water vapor when it gains enough energy from its surroundings. However, sublimation is the primary drying mechanism in this scenario as it allows the laundry to dry even while frozen. In conclusion, wet laundry hung on a clothesline on a cold winter day eventually dries due to the process of sublimation, where the ice formed in the fabric turns directly into water vapor, with evaporation playing a role if the temperature rises or residual liquid water is present.