An opportunity to look more extensively at the nature of crystals. Students are often fascinated by crystals especially if they can handle large ones.
Apparatus and materials
Alum crystal, large
Sodium thiosulfate crystals
Sugar crystals, type used for coffee
Health & Safety and Technical notes
Hands should be washed after handling crystals.
Ask students to handle the large crystals for themselves and closely examine the smaller ones.
Students should learn that crystals are identified by flat faces with angles between them. The angles are characteristic of that material, regardless of their size. They could be encouraged to look for crystals at home.
You may need to take precautions to avoid theft and breakage of the large crystals.
This experiment was safety-checked in May 2004