Final answer:
The moisture that forms inside a cold window is called condensation. It happens when warm, moist air inside contacts a cold surface, causing water vapor to become liquid droplets. It's also a key part of the water cycle through cloud formation and precipitation.
Step-by-step explanation:
The moisture that forms on the inside of a window on a cold day is called condensation. This occurs when warm, moist air inside the room comes into contact with the cold pane of glass, causing water vapor to cool and change into liquid water droplets. Condensation is a common example of a phase change where a gas turns into a liquid.
Condensation also plays a critical role in other natural processes, such as the water cycle. Here, water vapor rises in the atmosphere, cools, and then condenses to form clouds. Eventually, if the droplets in the clouds get big enough, they fall as precipitation (like rain or snow) back to Earth. Condensation and precipitation are essential for the replenishment of freshwater on our planet.