Three processes are: 1-Sublimation. 2-Deposition 3-Freezing 1-Sublimation:Not all solids melt upon heating.Some solids convert directly into gas without changing into liquid form.This is called sublimation.Dry ice is a solid form of carbon dioxide.It is used in refrigerators to keep things frozen.At room temperature,it does not melt,but changes into a gaseous state directly. 2-Deposition:At extremely cold temperatures,when the water vapor in the air comes into contact with objects like a windpane,it turns into ice instantly without ever forming liquid water.This is called deposition of gas partiles.Dry ice is also formed through the process of deposition. 3-Freezing:When a liquid is cooled until it converts into a solid,it is called freezing.Snowfall occurs when the temperature near the ground drops below the freezing point of water i.e 0°C.