When you exhale into a cold window pane, water vapor in your breath condenses on the glass. where does the water vapor come from?

Inside the lungs, condition is warm and wet. The warm air inside the lungs holds more moisture than cold air. Thus, exhaled air is warm and contains more moisture. Therefore, on breathing out on cold window pane, humid air loses heat get condensed on the cold window pane and the water vapor converted into water droplets.

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