Why do mirrors fog up after a shower?

Answer: Water vapor condenses on cold glass

Water vapor condenses on cold glass ✓ — Correct! Hot shower creates water vapor (invisible gas). When this vapor touches the cold mirror surface, it cools rapidly and condenses into tiny water droplets—that's the fog! It's the same process as dew forming on grass.

Soap residue attracts moisture — Wrong. Soap can make fogging worse, but fog forms because of temperature difference between hot air and cold mirror.

Mirror absorbs bathroom humidity — Wrong. Mirrors don't absorb moisture. The water you see is condensation from vapor cooling on the surface, not absorption into the mirror.