Crystals

Introduction:

Crystals are solids in which the smallest units (molecules, atoms or ions) that compose them form a repeating, three-dimensional pattern.  The shape of a crystal depends on the arrangement of the smaller units and the pattern that they produce.  Crystals are surprisingly common, and they are part of your everyday life.

Materials:

• Microscope (Compound or Stereo)
• Microscope slides
• Sugar
• Table Salt
• Sand (optional)

Instructions:

Look at salt and sugar crystals without the help of a microscope. Can you tell what shapes the crystals have? Do they have the same shape. To prepare a slide of table salt, place a few grains onto a side. View with the microscope under low power. If you are using a compound microscope, view only on low power because there is no coverslip (to help protect the lens); if you are using a stereomicroscope, you may increase the magnification.

Observe the shapes of the grains of salt. Prepare a slide of sugar the same way you prepared the salt slide. Again, be careful not to damage the microscope by touching the slide (or the sugar). Note that the sugar crystals have shapes that are different from the salt crystals. Salt crystals have a cube shape, while sugar crystals have a more oblong shape, similar to a column.