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Groups of 3-4 students follow this handout to create models of the 7 crystal systems and the 14 Bravais lattices using DOTS gumdrops, bamboo skewers and wood toothpicks.
| Attachment | Size |
|---|---|
| crystal systems and bravais lattices 2015 VIPEr pdf.pdf | 328.23 KB |
After completing this exercise, a student should be able to:
distinguish between the seven crystal systems
distinguish between primitive, body-centered, face-centered, and base-centered lattices
from a set of unit cell parameters, identify possible crystal systems
from space-group notation, identify a crystal as primitive, body-centered, face-centered, or base-centered
For one group creating 14 models:
Three 7.5 oz boxes of DOTS gumdrops (Tootsie Roll Industries, LLC)
Three packages of wood sticks in three different sizes: any combination of 12", 10", 6", or 4" bamboo skewers and/or 2 5/8" toothpicks
The activity is conducted during a single, 75-minute lecture period. Students documented their models with photographs and submitted the actual models in at the end of the class period.
It is used in conjunction with the Solid-State Model Kit sold by the Institute for Chemical Education - half of the class works with the ICE Solid-State Kit while the other half builds these models, and at the next class period the groups switch activities.
This activity is a skill-building exercise to prepare students for one requirement of a multifaceted term project: the description of the unit cell of a mineral structure in an oral presentation and term paper.
Evaluation
This activity was not graded. However:
- Students submit their gumdrop models at the end of the period. Time permitting, students adjust or re-build incorrect models.
- Follow-up question Q1 was used on a subsequent exam S2015 (I haven't tried Q2 or Q3 yet).
- Each student described at least one mineral structure in their term projects. The requirements included that they note the space group, the crystal system, the Bravais lattice, and the unit cell parameters in their description.