Snowflakes are crystals made from water and cold air.
A crystal is a solid matter wherein its molecules are arranged following a repeated pattern in three dimensions, thus creating its beautiful appearance. Crystals can be categorized in two ways, according to physical and chemical properties, or according to its crystalline structure or shape. Water plays a role in the formation of crystals because the shape and appearance of crystals depends on temperature, chemical components, water, pressure and the amount of space that allows its growth.
Crystal Formation
Crystals are formed naturally and artificially. Natural crystal formations depend on two time scales. The first is a geological time scale which includes minerals or gemstones and stalactites or stalagmites. The second is a regular time scale such as snowflakes and honey. Snowflakes are formed by water. Artificial crystal formations take place when a solution is supersaturated and the liquid evaporates leaving behind particles that bond together and grow to form the crystal structure. Crystals are formed synthetically by cooling the solution, adding a second solvent, chemical reaction, or change in pH level.
Kinds of Crystal Properties
There are four types of crystals according to its properties. Covalent crystals, like diamonds, have covalent bonds or chemical links between all its atoms. The melting point of this crystal is extremely high. Metallic crystals such as nickel and alloys have individual metal atoms on its lattices. These are dense and have high melting points. Ionic crystals are bound by electrostatic force which are hard and have moderately high melting points. Example of this is table salt. Molecular crystals are held together by non-covalent bonds. Crystals like table sugar and rock candy are of this kind of soft crystal with relatively low melting points.
Kinds of Crystal Structures
There are seven classifications of crystals according to structure or lattice. Isometric or cubic is the simplest where the unit cell takes the shape of a cube. Tetragonal are cube-like but with one longer axis in the form of pyramids and prisms. Orthorhombic are like two pyramids fixed together. Hexagonal crystals are six-sided prisms with a hexagon cross-section. Trigonal have a single three-fold axis of rotation. Triclinic have three unequal axes which take strange shapes. Monoclinic have a single two-fold rotation axis.
Water-Based Crystals
Ice is a crystal formation of water. There are fifteen crystalline forms of ice depending on the varying temperature and pressure. Examples of ice crystals are snowflakes, hails, glaciers, ice caps and others. These are classified by their crystalline structure, arrangement and density. Most liquids solidify at high temperature under pressure. But water freezes at a temperature below 0 degrees Celsius because of the strong hydrogen bonds. Ice can also stay frozen at temperatures above 0 degrees Celsius under low pressure.
Tags: melting points, crystal formations, crystalline structure, crystals according, Crystals formed, degrees Celsius, Formation Crystals
