Correct Option
The correct option isCondensation of atmospheric water vapour due to localized cooling.
Explanation
The phenomenon in question is governed by the physical process of condensation. This is the phase transition of matter from a gaseous state (water vapour) to a liquid state. It occurs when the temperature of the vapour is lowered below its saturation point (dew point) upon contact with a colder surface.
Statement-wise Analysis
- Seepage of water through the container walls. is Incorrect: Standard containers made of glass, steel, or plastic are impermeable solids. Water cannot pass or seep through the molecular structure of these materials unless they are porous (like earthenware) or damaged. The droplets appear on the outside, but the source is not the liquid inside.
- Condensation of atmospheric water vapour due to localized cooling. is Correct: The atmosphere contains moisture in the form of invisible water vapour. When this warm, vapour-laden air comes into contact with the ice-cold surface of the container, it loses thermal energy rapidly. As the air cools, its capacity to hold water vapour decreases. Once the temperature drops below the dew point, the excess vapour condenses into liquid water droplets on the outer surface.
- Evaporation of the liquid from inside the container. is Incorrect: Evaporation is the reverse process, where liquid turns into gas. If evaporation were occurring from the inside, the water would turn into vapour and mix with the air, not form liquid droplets on the outer walls.
- Differential atmospheric pressure forcing water out. is Incorrect: Differential atmospheric pressure is not the cause of this phenomenon. While pressure differences can drive fluid flow (as in a straw), the formation of droplets here is a thermodynamic process driven by temperature difference, not a mechanical process driven by pressure gradients.
Key Takeaway
Condensation is the conversion of atmospheric water vapour into liquid water when it comes in contact with a surface that is cooler than the surrounding air's dew point. This process releases latent heat.