Condensation forms on cold bottles from the refrigerator due to a natural process called "condensation," which occurs when warm, humid air comes into contact with a cold surface. Here's how it happens:
Humid air in the refrigerator: Even though the refrigerator is designed to maintain a cool temperature, there is still some level of humidity present inside. Humidity refers to the amount of moisture or water vapor in the air.
Temperature difference: When you place a cold bottle in the refrigerator, its surface becomes much colder than the surrounding air and the other items in the fridge. As a result, the cold bottle causes the nearby air to cool down.
Saturation point: Air can hold only a certain amount of moisture before it becomes saturated. The colder the air, the less moisture it can hold. When the cooled air near the cold bottle reaches its saturation point, it can no longer hold all the water vapor.
Condensation: The excess moisture in the air starts to condense into tiny water droplets on the cold surface of the bottle. This is the same process that creates dew on grass in the early morning or forms water droplets on the outside of a glass of ice-cold water on a hot day.
The condensation on the bottle occurs even if there are no food particles present because it's primarily a result of the interaction between the cold surface of the bottle and the humidity in the air inside the refrigerator. The same phenomenon can happen with any cold surface in a humid environment, such as windows in a heated room during winter or a cold drink on a warm summer day.