Introduction to Crystallization Chemistry

(Ferb, I know what we’re gonna do today)

CrystallizationCrystals are forms of solid matter that have ordered structures. Crystals often appear in a clearly geometric shape and many familiar things are crystals, including diamonds, graphite, salt, sugar, caffeine, and snow.

Crystal growth is accomplished through the process of self-assembly. Crystals like salt (halite) are made of ions. The resulting crystal formations are ionic crystals. Crystals made of atoms, such as silicon, are atomic crystals and crystals composed of molecules such as sucrose (sugar, C12H22O11) are molecular crystals.

CrystallizationCrystals can be grown from saturated solutions. Crystals grown as a result of self-assembly at the tiniest‖ level develop in a pattern representative of that matter. Therefore, salt crystals have a cubic structure while quartz crystals develop in a physical form of a six-sided prism with a 6-sided pyramid-shaped off-set point. Crystals have a repeating pattern based on unique chemistry and internal molecular structure. Snowflakes, the crystalline structure of water at a temperature below 0 ° Centigrade, form a six-sided structure while salt crystals are cubic in shape.

What is BoraxBorax is a mineral with many applications and was historically used in food preservation for many former civilizations. Borax is made up of little crystals that are generally white in color but can also be green, yellowish, brown or colorless. When it comes in contact with another object it will leave behind a chalky trail.

Borax’s scientific names are disodium tetraborate and sodium tetraborate – the “borate” inspired the common name, borax. Yet the real origins of the name date back thousands of years, where in Persia the word “burak” was used to identify borate salts. These salts which were used and discovered in the Middle East were embraced by the Romans which scattered early borax and its applications widely throughout Europe. Some important borax uses of the time including using it to preserve food (through the salting method), for cleaning, making pots, welding and in mummification.

Even now, borax still benefits the world in similar ways (although mummification has certainly gone out of style). The borax used nowadays is much more refined but is not as widely used as it once was. Although not toxic to the touch, borax is not meant to be eaten and especially in high amounts can be toxic and harmful.

http://www.youtube.com/watch?v=8BmYUkkQpCU

Questions

• List each material used in this project and identify the state of matter for each.

• Was this a chemical change or a physical change? Explain your choice.

• What role does temperature play in the process of crystallization?