By David Braunstein MESA Schools Program Academic Coordinator How are Crystals Made? By David Braunstein MESA Schools Program Academic Coordinator

Crystals MESA Specifications What are crystals? What materials can be used? What is the process for making crystals? What else is needed to be a winner? Experiment—MAKING IT CLEAR!

MESA Specifications Material to be used is Potassium Alum. AlK(SO4)2 . 12 H2O Also called Aluminum Potassium Sulfate Dodecahydrate. Crystal need to be large, clear, well-shaped, and beautiful. SOLUTION needs to be CLEAN. You need to WRITE what you do IN a LOGBOOK.

MESA Specifications (con’t) Growing time determined by the students. Display includes graph Crystal size (VOLUME) vs. TIME Take photos of Crystal growth during cycle. Size may be determined by Measurement Displacement Weighing and dividing by density (1.76 g/cm3) Write the data of the procedures and growth rate in the logbook.

What are Crystals? A solid formed by the solidification of a chemical and having a highly regular atomic structure (Sodium Chloride is an example of crystals e.g. Table Salt.)

Atomic Structure

Chlorine Structure

Sodium Structure

Sodium and Chlorine Ions Sodium, Na Sodium is also in Group 1. It has one electron in its outer shell. When this electron is lost, a sodium ion Na+ is formed. Chlorine, Cl Chlorine is in Group 7. It has seven electrons in its outer shell. It gains an electron from another atom in reactions, forming a chloride ion, Cl-

Sodium Chloride

Sodium Chloride

What is this?

Diamond Structure

GRAPHITE

BUCKY BALLS

ALUM CRYSTAL

Crystal Concepts Basic concepts Solvent- That which does the dissolving. (water) Solute- That which gets dissolved (sugar) Solution- Mixture of Solvent and Solute. Solubility-amount of a solute that can be dissolved in a solvent. The amount of sugar that can be dissolved in water.

GRAPH The graph demonstrates how various solutes have variable solubility according to the temperature of the solvent.

Flow Diagram for Growing Crystals SELECT MATERIALS Water soluble ionic salts WEIGH SALTS Use 10% over RT saturation data DISSOLVE Heat purified water to speed up dissolution-but not to boiling. Stir with a clean utensil i.e. glass rod. COOL TO RT If solution was saturated a few crystals will be on the bottom. FILTER This step will remove undissolved solids that will cloud crystals. GROW SEEDS There are several methods of growing clear seeds. The best is utilizing a Petri dish. Protect from contamination by covering with filter paper. GROW A BIG ONE Select a large, clear, well formed single seed. Tie string around the seed. Suspend it in a large volume of liquor and Replenish so as to keep the crystal suspended in the middle. PREPARE DISPLAY Board and log book

ALUM CRYSTAL