Study of Polymers, Measurement, Forces and Chemical Bonds

Spaghetti Strength

Study of Polymers, measurement, forces and chemical bonds

(from “Celebrating Chemistry,” American Chemical Society)

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(accessed Oct. 1, 2007)

Skills and Processes Involved

Materials needed (group of 25)

Various types of “string” pasta (spaghetti, thin spaghetti, linquini, angel hair, etc. Nice to use different brands, types (whole wheat, etc))
Pennies (or other weights—washers, marbles, candy). If pennies—20 per group is fine
Cup (paper or styrofoam)—1 per group
String or pipecleaners—1 per group (if string—25 cm works well)
Masking tape

Procedure

Talk to students about gravity and forces. Use pictures of bridges and ask—why doesn’t the bridge fall down (force upward by the bridge is equal to force down due to gravity on cars, people etc). Force upward has a limit—determined by structure of bridge.
Have students do introductory exercise.
Discuss with students their results. Ask key question:
”What can be done to increase the weight that can be applied? Possible variables:
Thickness of pasta (Angel Hair vs thin spaghetti vs regular spaghetti)
Shape of pasta (linquini (oval) vs. spaghetti (round))
Composition of pasta (regular vs whole wheat vs premium)
Density
Distance from table to cup
Height to drop pennies (bouncing action)
Number of strands of pasta.
“Pick one for your study. Develop the experiment.”
Have students develop their hypothesis and experiment to test hypothesis. Have limits as needed (no more than 4 strands of pasta used, etc). Have students draw data chart (if appropriate).
Have students conduct experiment and record results
As appropriate—graph results
Was hypothesis verified? Have students write in their scientific journals.
Have students draw their set-up

Extensions

Have students weigh each strand of spaghetti. Have them measure diameter (or give values).
Students can calculate volume of each strand (for round pasta—Vol = length x r2)
For Linquini (assuming oval cross section—elliptical cylindar) Volume is = length x  x a x b (where a is ½ of major axis and b is ½ of minor axis).
One study found that there were 812 pieces of regular spaghetti in one pound. Student can then calculate the volume of one pound of spaghetti. How does this compare with volume of box? Would you then expect to find the box full when opened? (From my calculations—one pound of spaghetti has a volume of 358 cm3. Volume of box is 525 cm3 (25 x 3 x 7 cm) Therefore, the box will be 68% filled by the spaghetti).
Can begin discussion of polymers (plastics). Starch is a polymer of glucose. What makes it “rigid?” Chemical bonds (Both intramolecular (covalent bonds) and intermolecular (cross-link). What happens when spaghetti is cooked? Why? (disruption of intermolecular bonds).