Dry ice is the solid form of carbon dioxide. Its cold because the freezing point of carbon dioxide is -190F. Carbon dioxide has a very large Solid to liquid and a quick liquid to gas ratio. When dry ice warms up it turns directly into a gas instead of water hence "dry ice". The best way to have fun with dry ice is to put it in the sink filled with water but be careful to have some ventilation because it is carbon dioxide and could knock you out from lack of oxygen.