Water evaporates from the back of an open fridge due to the principles of evaporation and condensation. Here's the scientific explanation behind this process:
Evaporation: Evaporation is the process by which a liquid, in this case, water, changes into a gas (water vapor) when it gains enough energy. The molecules in a liquid are in constant motion, and some of these molecules at the surface have enough kinetic energy to break free from the liquid's surface and enter the air as vapor.
Humidity: The air around us contains water vapor in the form of humidity. The amount of water vapor the air can hold depends on the air's temperature. Warmer air can hold more water vapor than colder air.
Inside the fridge: Inside a refrigerator, there are various items stored at cool temperatures. When you open the fridge door, the warmer ambient air from the outside comes into contact with the cold surfaces inside the fridge, including the cooling coils.
Condensation: As the warm, humid air comes into contact with the cold surfaces, it cools down rapidly. Colder air cannot hold as much moisture as warmer air, so the excess moisture in the air condenses into liquid water droplets on the cold surfaces. This is the same process that causes condensation on a cold glass of water on a hot day.
Evaporation at the back: Now, here's where the water at the back of the fridge comes into play. The fridge's cooling system, including the compressor and coils, cools down the air inside the fridge. As a result, any water that has condensed on these surfaces can start to evaporate again when the fridge is running, adding moisture back into the air inside the fridge.
Ventilation: In a well-designed fridge, there's a certain level of ventilation and air circulation. The moisture-laden air inside the fridge, which may have evaporated from the cooling coils, gets expelled from the back of the fridge due to this circulation. As the moist air is released into the warmer surroundings outside the fridge, it continues to evaporate and disperse into the atmosphere.
This process of evaporation and condensation is an essential part of how a refrigerator functions to keep the contents cool and dry. However, it's worth noting that excessive condensation or water pooling at the back of the fridge could indicate a problem with the fridge's cooling system or a faulty seal, which may require maintenance or repair.