Correct Option
The correct option is 2 only.
Explanation
Condensation is the process by which water vapour in the air transforms into liquid water. This phase change is driven by the loss of heat and the saturation of air. In the atmosphere (free air), this process is governed by temperature, volume, pressure, and the presence of particulate matter.
Statement 1 is Incorrect:
Condensation in free air does not occur independently of hygroscopic condensation nuclei. Water vapour requires a surface upon which to condense. Suspended particles such as dust, smoke, and salt act as these nuclei. Without them, air can become supersaturated without condensation occurring. Hygroscopic nuclei (water-attracting particles) are particularly effective, allowing condensation to begin even before the air reaches 100% relative humidity.
Statement 2 is Correct:
Condensation takes place when the air becomes saturated with moisture. Saturation occurs when the temperature of the air drops to the dew point (the temperature at which the air can no longer hold all its water vapour). Therefore, the process is directly linked to the temperature being close to or reaching the dew point.
Statement 3 is Incorrect:
It is factually incorrect to state that condensation never occurs if air volume is reduced. According to standard physical geography principles, condensation can take place under three specific conditions:
- When the temperature of the air is reduced to the dew point with its volume remaining constant.
- When both the volume and the temperature are reduced.
- When moisture is added to the air through evaporation.
Key Takeaway:
Condensation in the atmosphere requires hygroscopic nuclei and occurs when air is cooled to its dew point. It is primarily caused by adiabatic cooling (expansion of air), but can technically occur if both volume and temperature decrease.