The Sweating Scooter Seat

The story

Kabir noticed his scooter seat was soaked one morning, even though the sky had stayed clear overnight. He wondered if he had left a bottle open, but Riya pointed out that no one had touched the seat and the grass nearby was also wet with dew. Oddly, the cement next to the scooter was dry. Kabir guessed it was just Pune’s famous humidity making everything sticky, but Aaji suggested keeping an eye on the seat at sunrise. Thinking it through, Riya realised the seat cooled down more than the air itself. Could water in the air really turn into drops on a cold surface? It seemed like science magic. The real question was: would the same thing happen if the scooter was parked inside all night?

The science

The answer is condensation. At night, the scooter seat loses heat to the open sky and becomes cooler than the surrounding air. If the seat's temperature falls below the air’s dew point, water vapour in the air condenses on it, forming liquid droplets called dew. This process happens on objects exposed to the sky, like grass or car roofs, but not on surfaces under shelter, since they don’t get cold enough. The textbook calls this phenomenon condensation and links it to the concept of dew point.

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