TEACHER:

Marcella Vancil, kindergarten and first grade
Flossie Wiley Elementary School
Urbana, Illinois

AGES:

Six to Nine

PROJECT:

Construct models of six common crystal structures

GOAL:

To learn some of the geometric patterns and shapes that form inorganic substances

After 18 years in the classroom, Mary Vancil never questions why she chose her profession. "I teach because I love it," she says. "I believe what so many people just say: Children are our world's greatest resource." Teaching also allows Vancil to to continue learning more about the world around her.

Vancil introduces the crystal-building project to students to drive home the point that all rocks and minerals are made of crystals. Looking at the shapes of different minerals, like simple table salt, under a microscope tends to inspire a greater appreciation of everyday, often ignored substances. "This is the kind of learning I love," says Vancil. "It teaches children how to find answers, and how to ask questions."

MATERIALS
• Toothpicks
• Jelly beans or mini-marshmallows



INSTRUCTIONS
1. If you choose to work with mini-marshmallows, spread them on a cookie sheet and let them harden overnight.

2. Show your children the picture of the model on this page or let them choose their own shape based on a molecule they may have seen in a book or in the classroom. Have them estimate how many toothpicks and marshmallows they'll need to construct the shape. Translating something from two to three dimensions is an important skill in itself.

3. As you build, tell your kids how geologists use different words to describe crystals. A face is a crystal's flat side; a vertex is the corner or point, represented here by a jelly bean; an edge is the border that connects vertices, or the toothpicks in this case. Ask your children how many faces, vertices and edges are on each crystal they're building. Invite them to recognize basic shapes in these crystals, too. Are there squares or triangles in the models they're making? Geologists classify crystals by their symmetry. How can you cut the crystal so that both halves look the same? Are there different ways to do it?

4. Look for patterns. For example, two square pyramids make up an octahedron. How many square pyramids fit together to make a cube? How is a cube like a tetrahedron?

5. Invite your children to notice crystal shapes in the world around them. How do we use these shapes in the construction of buildings? Can you find them in the structures that animals build, such as wasp nests and spiderwebs?

6. Find out what these shapes add up to in real life. For instance, a hexagonal prism is the basic building block of tourmaline, diamond crystals have an octahedron pattern, while table salt has a cubic pattern.