Ice

Ice is the solid form of water. The phase transition occurs when liquid water is cooled below 0 (273.15 K, 32 F) at standard atmospheric pressure.

An ice cube is a small, roughly cube-shaped piece of ice, conventionally placed in drinks to cool them down. Ice cubes are often preferred over crushed ice because they melt more slowly; they are standard in mixed drinks that call for ice, in which case the drink is said to be "on the rocks."

Ice cubes are produced domestically by filling an ice cube tray with water and placing it in a freezer. Many freezers also come equipped with an icemaker, which produces ice cubes automatically and stores them in a bin from which they can be dispensed directly into a glass. Ice cubes made by automatic icemakers are generally longer and thinner, requiring less force to remove them from the tray.

Ice cubes are also produced commercially and sold in bulk; these ice cubes are often cylindrical, and may have holes through the center. An interesting characteristic of commercially made ice cubes is that they are completely clear, lacking the clouding found in the center of domestically made ice cubes. This is due to the machine forming the cubes in thin layers, instead of all the water that the ice cube consists of being frozen at once.

Cloudy ice cubes result when water is frozen quickly. When water is cooled slowly (or very close to its freezing point), dissolved gases and microscopic bubbles have a chance to exit the water. However, when water is cooled quickly (further below its freezing point, a situation found in most home freezers), those small bubbles are simply frozen in place.

Melting ice cubes sometimes precipitate white flakes. This is calcium carbonate which is present in many water supplies and is completely harmless.

Traditionally, drinks in Europe are served without ice. In India and other parts of the world, it has traditionally been viewed as unhealthy to drink a libation with ice. Many older Indians still refuse to use it.