Molecules, such as water or H2O, are held together by forces with varying degrees of energy. That energy level dictates the current state of the molecule; either solid, liquid or gas. When you put a molecule like water into a freezer, energy is lost from the molecules as the speed of the electrons and other atomic particles slow.
Solids are at a lower energy state then a liquid as liquids are at a lower energy rate than a gas, so as the water in the freezer gets colder, its structure begins to change. Because of the strong hydrogen bonds when water freezes it configures itself in such a way as to maintain the lowest possible energy level resulting in an ice crystal’s unique formation.
To put simply, cold decreases energy levels which prompts liquid H2O to drop to a lower energy form, ice, which always forms the same way.
Now let’s talk about what is going on with a commercial ice machine like you’d find at a restaurant or a hotel.
A commercial refrigerator really consists of three basic components: a refrigeration unit, a water supply and a compartment to collect the ice. First off, a metallic ice tray is cooled through a series of temperature controlling pipes within the refrigeration unit. A water pump, tapped directly into the building’s water supply, pumps water onto the cold tray.
Since the metallic plates are already under 0 degrees, the introduced water quickly freezes and builds up on the frigid ice tray and a number of ice cubes are formed. Every few minutes or so, an automated valve rapidly changes the temperature of the tray to quickly heat it so that the built-up ice cubes are suddenly dislodged.
The cubes then either slide into the containment section or are forced out by a driving piston that jars them free.
Then you trudge in wearing slippers and scoop a bundle of ice from the freezer unit for the champagne waiting to be chilled in your hotel room.
Quick rerun: water’s poured on a big freezing metal ice cube tray, turns into cubes, then are heated in order to dislodge them and sent to rest in a refrigerated storage unit. Simple, effective, and totally necessary to have in your kitchen.