Ice cubes are small, roughly
cube-shaped pieces of
ice, conventionally used to cool
beverages. 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 out of a tray are generally longer and thinner, requiring less force to remove them from the tray and thereby reducing the likelihood of the cube becoming stuck in the dispenser.
There are also dedicated ice-maker machines used to produce ice cubes for laboratories and academic use. Ice cubes are also produced commercially and sold in bulk; these ice cubes, despite their name, 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.
Cloudy ice cubes result when water is frozen quickly, or ice is allowed to form on the surface of the water. When water is cooled to its freezing point, and ice starts to form, dissolved gases can no longer stay in solution and come out as microscopic bubbles. However, as ice floats in water, once there is enough ice to form a layer on the surface, the ice layer traps all bubbles within the ice cube. Ice-makers use a flowing source of water to make ice with cooling elements at the bottom, allowing the bubbles to be washed away from the top as the cube grows.
