A sodium chloride crystal is cleaved by striking it sharply with a pestle.

Curriculum Notes 

This can be used as a projected demo or as a small group activity for a class to demonstrate the crystalline properties of some solid materials such as ionic compounds. It might be useful to display an ionic model of the sodium chloride crystal with this demo.

One day of lead time is required for this project.

Discussion 

The regular planes of cleavage of a crystalline solid corresponds to the orientation in space of the species which comprise it. 

Materials 

• small plastic box with lid
• halite (sodium chloride) crystal - large halite crystals can often be obtained from colleagues in the earth sciences
• ring stand base
• pestle
• impact goggles

Procedure 

While the crystal is resting on the ring stand base, strike it sharply with the pestle to cleave off a portion. Leave the crystal and base in the box to contain the fragments. 

Safety Precautions 

Wear impact goggles for this demo to protect your eyes.