When a person wearing glasses enters a warm house after being outside on a cold day, their glasses fog up because of A. Condensation B. melting. C. evaporation D. sublimation
The correct answer and explanation is:
The correct answer is A. Condensation.
When a person wearing glasses comes inside a warm house after being outside in the cold, their glasses fog up because of condensation. Here is how this happens:
Outside, the air is cold and usually holds less moisture because cold air cannot hold as much water vapor as warm air. When the person steps into the warm house, the warm indoor air contains more moisture in the form of water vapor. The glasses, however, are still cold from being outside.
When the warm, moist air inside the house touches the cold surface of the glasses, the temperature of the air near the glasses drops. As air cools, it can hold less moisture, so the water vapor in the air changes from a gas to tiny liquid droplets on the surface of the glasses. This process of water vapor turning into liquid droplets on a cooler surface is called condensation.
Melting refers to a solid turning into a liquid, which is not happening here since the fog on the glasses is not ice or a solid form. Evaporation is when a liquid changes to a gas, like water turning into steam, but in this case, water vapor is turning into liquid droplets, so it is the opposite of evaporation. Sublimation refers to a solid turning directly into a gas without becoming liquid first, such as dry ice turning into carbon dioxide gas, which is also not occurring here.
Therefore, the fog on the glasses is caused by condensation because the warm moist air meets the cold surface of the glasses, causing the moisture to turn from gas to liquid droplets, which appear as fog. This is a common everyday example of condensation.