Putting a wet paper towel around a can and placing it in the freezer can cool it faster due to a process called evaporative cooling. Evaporative cooling occurs when a liquid evaporates and the process requires energy. As the liquid evaporates, it absorbs heat from its surroundings, including the can, which results in a cooling effect.
When you wrap a wet paper towel around a can and place it in the freezer, the water in the towel starts to evaporate. The freezer's cold temperature facilitates the evaporation process. As the water molecules on the surface of the wet paper towel gain enough energy to escape as vapor, they take away heat from the can. This heat transfer occurs because the energy required for the phase change from liquid to vapor is obtained from the surrounding environment, which, in this case, is the can.
The wet paper towel acts as a medium to facilitate the transfer of heat from the can to the evaporating water. The towel provides a larger surface area for evaporation to occur, allowing for more efficient cooling. Additionally, the wet paper towel maintains contact with the can, ensuring continuous heat transfer as long as there is moisture available for evaporation.
The cooling effect of evaporative cooling is similar to the sensation of feeling cool when you sweat. When sweat evaporates from your skin, it absorbs heat from your body, providing a cooling effect. Similarly, the evaporation of water from the wet paper towel absorbs heat from the can, cooling it faster than if it were left in the freezer without the towel.
It's worth noting that while the wet paper towel method can accelerate the cooling process, it's essential to monitor the can to prevent it from freezing and potentially bursting due to expansion of the liquid inside.