Problem 25 - Chemistry An Atoms First Approach

Question

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

Step-by-Step Solution

Answer

In cold winter temperatures, water in the wet laundry freezes into ice. However, due to a process called sublimation, the ice in the frozen laundry can directly convert into water vapor without going through the liquid state. This is possible in low humidity and cold temperatures, where the sun's heat and air temperature facilitate the sublimation of ice to water vapor. Additionally, if the humidity in the air is low, the surrounding air can absorb the moisture as the ice turns into water vapor. As the frozen laundry continuously loses moisture through sublimation, it eventually becomes dry.

Step 1: Understanding the properties of water

Water exists in three states: solid (ice), liquid (water), and gas (water vapor). In cold winter temperatures, water in the wet laundry will freeze into ice when the temperature drops below the freezing point of water (0°C/32°F).

Step 2: Frozen laundry and sublimation

When the wet laundry freezes, the water molecules in the laundry are transformed into ice. However, there is a process called sublimation, in which a solid directly converts into a gas without going through the liquid state. This can happen to the ice in the frozen laundry, particularly in low humidity and cold temperatures.

Step 3: Factors affecting sublimation

There are two factors that play a crucial role in the sublimation process: 1. Temperature: Even though it's cold, the sun's heat and possibly the air temperature are still present. This heat facilitates the sublimation of ice directly to water vapor. 2. Humidity: If the humidity in the air is low, the air has the capacity to absorb moisture. The frozen laundry will lose moisture as the ice turns into water vapor, which will be absorbed by the surrounding air.

Step 4: Final explanation

As a result of sublimation, the frozen laundry loses its moisture content in the form of water vapor. Continuously losing moisture eventually leads to the laundry becoming dry. This is why wet laundry hung on a clothesline on a cold winter day will freeze but eventually dry.