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Science Experiments for the Strength of Rubber Bands

Rubber bands are known for elasticity. They can stretch and return to their original shape, but will reach a point of failure when they are stretched too much. Different rubber bands will have different breaking points because of their size and composition, but other factors can affect their strength, too. Through experimentation, your students can find different factors that might make rubber bands weaker or even stronger.

Basic Strength Test
- The most basic experiment involves hanging objects from rubber bands until the bands break. Start with several identical rubber bands. Loop one rubber band over a supported bar and hang an object from it. Use an object like a cup or plate that you can add weight to incrementally. First weigh the plate or cup, then record the added weight that it takes to break the rubber band. You can use items like small fishing weights or pre-measured amounts of sand to add weight. Repeat with different types and sizes of rubber bands to compare their strengths.
Different Temperatures
- Temperature may affect rubber bands' strength. You can subject rubber bands to different temperatures in a variety of ways, and this can be done before or during a test of a rubber band's strength. Try heating or freezing a rubber band before subjecting it to a strength test or performing a strength test while changing the temperature of a rubber band. One way to do this is to hang a weight from a rubber band that is totally immersed in water. You can change the temperature by adding large quantities of ice to cool the water and the rubber band, or you can easily heat the water and rubber band if you position it over a stove or Bunsen burner.
Different Solutions
- Try soaking rubber bands in different solutions or chemicals before testing their strength. Motor oil, bleach, ammonia and gasoline are just a few ideas. Some solutions may interact with the rubber in ways to make them stronger or weaker. Some solutions may have no measurable effect at all. Soak the rubber bands in different solutions for extended but finite and measured periods of time before subjecting them to strength tests. For instance, you might soak a rubber band in bleach for two hours, but not for "a few minutes." You might even soak a rubber band in motor oil for 24 hours, but make sure you register the exact time you have soaked the rubber bands.
Reliability and Validity
- Whatever experiments you choose to perform, it is essential to ensure that the experiments are reliable and valid. Reliable experiments get similar results when performed multiple times. So perform each experiment multiple times with identical rubber bands. Ensure validity by changing only one variable or factor at a time. For instance, if you soak a rubber band in bleach for an hour and then freeze it, you will have no idea if the temperature, the bleach or a combination of the two affected the rubber band's strength.

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