Edible Engineering

Build structures with your Halloween candy before you eat it!

What you will need:

Variety of candy pieces, preferably gummy (e.g., gumdrops, jelly beans, or fruit snacks)

Toothpicks

Here’s what to do:

  1. Remove the wrappers from a mix of different candy shapes.
  2. Using candy, start building different structures.
  3. Try building the tallest tower or longest bridge you can.
  4. Use toothpicks to connect candy pieces to make more structures.
  5. Build a geodesic dome with 11 candies and 25 toothpicks:
    • First, use 5 candies and 5 toothpicks to make a pentagon (5-sided figure).
    • Stick 2 more toothpicks upright in each candy like a V-shape with the tops of neighboring toothpicks touching.
    • Add 5 candies, 1 to connect each pair of toothpicks from the V tops, to form 5 triangles with the pentagon toothpicks as the bases of the new triangles.
    • Connect the candies on the top with toothpicks to form another pentagon.
    • Stick 1 toothpick in the top of each of the top candies pointing up.
    • Connect these 5 toothpicks in the middle with 1 final candy.
    • Gently press on the top of your dome. How strong is it? Can it hold a small book?

Take it further:

  • Which shapes are strongest: squares & cubes, triangles & pyramids, or circles & spheres?
  • How tall can you build with just 5 pieces of candy and 10 toothpicks?
  • Can you build a structure that holds a heavy book? What shapes work best?
  • Try to draw a blueprint (diagram) for your structure. How could you draw it on paper so someone else could build the same thing?

What’s going on?

You probably discovered that squares & cubes easily collapse when too much weight is put on top (compression). Round shapes like circles & spheres or, more commonly in architecture, arches & domes are stronger than squares, but you may have discovered that triangles make the strongest structures. The pyramids in Egypt are based on triangles and have stood for centuries! Have you ever climbed on a geodesic dome at a playground? The triangles give it strength!

Triangles are strong shapes for engineering structures because compression on one side of the triangle is balanced by a pull (i.e. tension) on the other side, so the whole structure can’t collapse like a square. The way to squash a triangle is to break one of the sides, which requires a lot of weight!

If you tried to build a tall tower out of cubes, how did it hold up when you added weight to the top? Try to build the tower again, but this time add toothpicks inside the cube between opposite corners to make triangles inside the cube; this should make your tower stronger. Can you think of any other structures you’ve seen that use triangles for strength?

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