How can a wet towel dry at room temperature?
Water molecules can escape from a liquid's surface into the air even below boiling temperature. This surface process is evaporation, and it can cool what remains.
- The scientific idea
- Evaporation
- Fields of science
- Physics
How it works
A damp towel does not need to reach 100 °C to dry. Water molecules are continually moving, and some at the surface have enough energy to escape their neighbors. The water becomes vapor even though no bubbles form inside it.
Look closer
That escape requires energy. When water evaporates from skin, some of the energy comes from the skin, producing a cooling effect. This is why being wet can feel cold even when the water was initially warm. Condensation runs in the opposite direction, returning vapor to liquid. Drying occurs when, overall, more molecules leave the wet surface than return to it. Water has changed where and how it exists, rather than disappearing.