Shapes Lab Educator Support
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After doing the Shapes Lab, have kids do this hands-on activity to apply what they've learned about shapes.

Straw Shapes

Introduce the Activity
Give kids the straws and paper clips. Ask them to brainstorm a list of adjectives describing the straws as a building material. Ask: How do the straws bend? How useful do you think straws are as a building material? (Kids will probably say not very useful.) Discuss how the straws' stability might change depending on how they are used.

Lead the Activity

• Demonstrate how to connect straws with paper clips.
• As groups finish building their shapes, talk about their plans for testing the strength of the shapes. Will one person do the testing, or will they take turns? How can they make the test as "fair" as possible? (The same person, or both people, should test both structures.)

The Big Idea
Straws arranged into triangles form a more stable shape than straws arranged in squares. A triangle changes shape less than a square when compression force is applied to the joints. When compression is applied to a square, the joints easily rotate, and the shape changes. In a triangle, however, the compression in the two sides is balanced by the tension in the cross-piece at the bottom, which pulls the sides back together. This balancing of forces results in a more stable structural form.

To reinforce the use of triangles in structures, have kids go on a "shape" scavenger hunt through the Wonders of the World Databank or during their daily travels, looking for examples of shapes used in structures. Good places to see triangles are in the cross-braces of scaffolding, and in trusses under bridges and railroad overpasses.