SCIENCE:

Jelly Bean Crystals

           

Today's Snack: Make a Jelly Bean Sundae - tear small pieces of angel-food cake into a small bowl or cup, add several quartered strawberries, drop in a scoop of vanilla ice cream, and top with a handful of jelly beans.

 

 

--------------------

 

One magnifying glass or microscope per student, or small group

 Salt | black or dark-colored paper napkins or cloths

Water | at least 24 toothpicks per student

At least 16 jelly beans, 8 each of two colors, per student

 

 

1. Shake out a little bit of salt onto a dark-colored napkin or cloth and observe with a magnifying glass or microscope. Salt is shaped in crystals. Each tiny salt crystal is shaped as a cube.

 

2. That cube shape is determined by the way the sodium and chlorine atoms that make up salt bond to each other. You're probably familiar with sodium, but did you know about the other element, chlorine? It's what keeps swimming pools healthy and clean.

 

3. It's amazing to know that each tiny atom of salt is also shaped as a cube. They bond together to form the tiny salt crystal cube that you can see. But all the way down to the atomic level, they are cubes, too. Millions of tiny salt crystal cubes bond together to form the salt crystal cube that you can see.

 

4. Now let's build a model of salt crystal cubes! Count out 24 toothpicks to represent the chemical bonds in one cube. Also count out 16 jelly beans, eight of one color and eight of another. These jelly beans will represent atoms of sodium or chlorine. Decide which color to assign as sodium, and which to assign as chlorine.

 

 

5. Here's the puzzle: you need to build a six-sided cube with two toothpicks on each edge. The double toothpicks represent the bond between sodium and chlorine that forms the cube shape, as do the two different-colored jelly beans at each joint of the cube.

 

6. The trick is, no toothpick should join the same color of jelly bean on its two ends. The colors should alternate, just as the sodium and chlorine atoms do when they bond. Sodium doesn't bond with sodium; it bonds with chlorine. And vice versa! So the colors should alternate.

 

7. Last, but not least, the cube should be "built" solidly enough so that the length of each edge is the same. It should look like a perfectly squared-off cube, not lopsided. It's amazing how perfectly tiny crystal atoms hold their shape. That shows the power of the chemical bonds between them!

 

8. Hint: line up two toothpicks fairly close together, and push two colors of jelly beans on the ends of them. Then alternate the colors on a second one, and join them together. You should end up with a square of double toothpicks joined with two jelly beans at each corner. If one toothpick goes into a red jelly bean on one corner, representing a sodium atom, then that toothpick needs to go into a green jelly bean on the adjoining corner, representing a chlorine atom.

 

9. It may sound confusing, but once you make one square, you're home free. Now just make another one. When you have two squares, join them with double toothpicks as vertical pieces to form a cube. Remember, each toothpick needs to join two different colors of jelly beans.

 

10. If you have enough jelly beans and toothpicks, you can make your model larger by adding more of the same structure to your cube. This is exactly how salt molecules join up until the crystals are large enough to be visible. Can you make a four-cube structure? A 16-cube structure?

 

11. Let your model air dry. And next time you put salt on your popcorn, you'll know exactly what you're eating, down to the atomic level!

By Susan Darst Williams • www.AfterSchoolTreats.com • Science 08 • © 2010