Sometimes, in cool weather, the insides of our windows look cloudy. They are covered with a thin film of water. Where does this water come from?
It comes from water vapour, water molecules mixed with the air inside the house. The water collects on the windows when the glass is cool.
Water vapour is a gas. The molecules of water vapour are as warm as the air around them in the house, so they move very fast. But when the molecules hit the cool glass in the window, they lose heat. As the molecules grow cooler, they move closer together and slow down. When they are moving slowly enough, they condense, or turn into tiny drops of liquid water.
Sometimes when the weather is very cold, the glass in the windows gets much colder than the air inside the house. Then the molecules of water vapour lose even more heat when they touch the glass. They slow down much more and move much closer together. When they get close enough to pull hard on one another, they freeze. Then the window is covered with frost – thin, feathery bits of solid ice.
Picture Credit : Google