Eis

Eis is the German noun for ice, the solid phase of water (H2O). As a substance, it forms when liquid water loses enough thermal energy to overcome molecular interactions that hold it in the liquid state. Under standard atmospheric pressure, the transition from liquid to solid occurs at 0 degrees Celsius (32 degrees Fahrenheit), a temperature known as the melting/freezing point.

At the molecular level most natural ice is crystalline and forms a hexagonal lattice, referred to as ice Ih. There are numerous higher-pressure phases of ice (ice II, III, V, VI, VII, etc.), collectively called ice polymorphs, which occur only under specific pressure and temperature conditions and are not typical of ordinary surface ice.

Compared with liquid water, ice is less dense, which causes it to float. It is usually transparent when pure and formed gradually, though impurities or air inclusions can give ice a cloudy or opaque appearance. Ice is a poor conductor of heat and has a relatively high heat of fusion, about 6.01 kilojoules per mole, as well as a specific heat capacity of about 2.1 joules per gram per kelvin.

Ice forms and melts according to temperature and pressure. At standard pressure, the solid ice melts to liquid if heated above 0 °C, and freezes from liquid when cooled below that temperature. The presence of salt or other substances lowers the freezing point, a principle used in de-icing and antifreeze applications.

Uses and significance: Ice is widely used for cooling, food preservation, and in climate research as sea ice and glacial ice provide information about past and present climate. In everyday life, ice appears in frozen desserts and drinks and features in sports and transportation (ice rinks, ice roads) and art and culture.