Explain why a bathroom mirror fogs up when you take a hot shower or bath?

Answer 1

When that happens, condensation is occurring. Condensation turns a gas in to a liquid. In this case the gas is the water vapor. When the cold mirror cools the water vapor and when the water vapor and the air next to the mirror becomes cool enough, it then changes to a gas into a liquid. That's why it becomes wet and fogged up.
Is this something I can put on the mirrors to keep them from fogging up when I'm taking the shower The mirror becomes fogged due to the moisture that accumulates in the air due to the heat of the water. Soon it reaches dew point and condenses on cooler surfaces such as the mirror or window causing water to form.
The hot water evaporates into steam. When the steam hits the cold surface of the mirror, it forms condensation. The condensation is what you see as the fog.

Improvement.

Steam is water in its gaseous phase, and is (like most gases) invisible. Steam only exists above the boiling point of water, so being immersed in true steam would cause near-instant death.

What you see in the bathroom with a hot shower is fog: microscopically small droplets of liquid water.

These will readily condense on any cool surface, but condensation on a shiny, smooth surface (the mirror) is the most noticeable.

If you run your hand over a marble or laminated benchtop, you'll be able to see the track left behind in the water film.

Answer 2

When you take a hot shower or bath, the warm, humid air in the room comes into contact with the cooler surface of the mirror. The temperature difference causes the warm air to cool down quickly on the mirror's surface, leading to condensation forming in the form of small water droplets that make the mirror appear foggy.

Answer 3

porque el vapor procedente del agua caliente se queda suspendido en el aire, condensándose en las superficies más frías como, por ejemplo, el espejo del baño.