Which process begins first when moisture-laden air cools?

Correct answer: Condensation

Answer: B, condensation. Moisture-laden air already contains a considerable amount of water vapour. When it cools, the maximum amount of vapour that the air can hold decreases. As cooling continues, the air may reach saturation. Any further cooling or excess vapour then changes into tiny liquid droplets, and this change is condensation. A, evaporation, is liquid water changing into vapour and is not the first process described by cooling moist air. C, runoff is the movement of water over land after water reaches the ground; it is not an immediate atmospheric change caused by cooling. D, an earthquake is a movement of the Earth’s crust and has no necessary connection with moist air cooling. In nature, cooling and condensation may be followed by cloud formation and possibly precipitation, but the first relevant process here is condensation. Memory cue: cooling moist air reaches saturation and then condenses.