Sand Structures

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Sand Structures
  • Age: 8+
  • Time: 75
  • (Setup: 10 min, Activity: 60 min with wait time, Cleanup: 5 min)
  • Materials: $18

In this mission you’ll find out how properties of individual ingredients can make different properties of a mixture-and maintain their own molecular structure while they’re at it! You’ll do this by making and comparing little sand towers.

Download PDF
  • what you need
    WHAT YOU NEED

    Materials:

    • Permanent marker
    • 3 index cards, cut in half
    • 1/3 cup water
    • 1/3 cup hand sanitizer
    • 1/3 cup vegetable oil
    • 4 cups of sand
    • 100 pennies (one $1 roll)
    • Data sheet (found on PDF)

    Equipment:

    • 1/3-cup liquid measuring cup
    • 1-cup dry measuring cup
    • 8 disposable 3-ounce paper cups
    • 4 paper plates
    • 3 paper bowls
    • 3 plastic spoons

    Note: The printable PDF for this experiment includes a data sheet for marking observations.

  • What To Do
    WHAT TO DO
    1. With the marker, label four paper cups like this: “Sand,” “Sand + Water,” “Sand + Hand Sanitizer,” and “Sand + Vegetable Oil.”
    2. Label four paper plates with the same names as the cups, leaving the middle of the plate open.
    3. Label three paper bowls as well with: “Water,” “Hand Sanitizer,” and “Vegetable Oil."
    4. Pour 1/3 cup of each liquid into its labeled bowl. Add 1 cup of sand to each bowl. Stir each mixture with a spoon. How do the liquids mix differently?
    5. Fill and press each mixture into its labeled paper cup. The cup labeled ‘Sand’ should be filled with dry sand. This will be used as a comparison to the other mixtures, or as scientists say, the control. Allow the filled cups to set for 45 minutes.
    6. Once the cups have set, place the paper plate labeled with the correct mixture face down over each cup. Holding from the top and bottom, flip each one over so the plate is now underneath the cup and place it back on the table. Lift the cup away to reveal the sand structure. What differences do you observe as you remove the cups?
    7. Based on your observations so far, can you predict which sand mixture will hold the most weight? Place half of an index card across the top of each remaining sand structure and put an empty paper cup on top. Start adding pennies to the cup and record the number of pennies it takes for each structure to collapse. Were your predictions accurate?

    Cleanup: Wash measuring cups. Throw used paper products and sand mixtures in the trash. Save any extra unused sand, hand sanitizer and vegetable oil for other purposes. And save your pennies!

  • What's Happening?
    WHAT’S HAPPENING?

    Notice that the sand or any of the liquids by themselves can’t hold very many pennies. Once the sand is combined with a liquid, the sand structures are able to hold much more. The mixing of the sand with a liquid created a substance which is stronger than either of the individual starting materials. For our sand structures, this is due to the forces with which the molecules of each material stick to each other. Each liquid has forces of different strength at play, resulting in each mixture being able to support a different amount of weight.

  • So What?
    Photo of one long, narrow white concrete bar stacked on top of another, with a thick spring in between. The top bar is filled with a stripe of blue material down the middle.

    Image credit: Charles Bakis/Penn State

    SO WHAT?

    Composite materials are those which combine two or more materials and when combined have properties that are unique to their individual parts. In your experiment, the combinations resulted in greater structural stability. Other composite materials result in new properties of weight, strength, and more. This ability to create a mixture which is greater than the sum of its parts presents great possibility to create materials with useful properties for a wide range of applications. For example, the concrete inside of a bridge is a composite made of sand, water and cement. For another example, carbon fiber composites combine ultra-thin strands of carbon with different polymers to create high strength and low weight materials that can conduct electricity. Using different combinations, carbon fiber composites can be found in wind turbine blades, aircraft, sports equipment and high-performance cars, and even potentially artificial skin.

  • Scientists In Action
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    Scientists In Action

    Driven over a bridge lately? Thank engineers like Charles Bakis. Fascinated by the ways that materials work when they’re mixed together, Charles now works to make sure that bridges and other structures are safe.