Rubber Band Elasticity and Temperature
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Project Summary
| Difficulty | 6 |
| Time required | Very Short (a day or less) |
| Prerequisites | None |
| Material Availability | Readily available |
| Cost | Very Low (under $20) |
| Safety | Adult supervision required for using utility knife |
Sponsor
| Sponsored by a generous grant from Seagate |
|
Objective
The goal of this project is to investigate how the restoring force of a rubber band varies with temperature.
Introduction
All matter is made up of atoms, like carbon, or hydrogen, or oxygen. Atoms are linked together to form larger compounds called molecules. Some molecules are made by stringing together repeated subunits. Such molecules are called polymers. In some polymers, including many synthetic polymers in textiles and plastics, the subunits are identical. In other polymers, such as proteins manufactured inside cells, the subunits have a common 'backbone' structure, to which different chemical groups are attached.
Rubber is an example of a natural polymer. The chains of molecules in rubber have a natural elasticity: they can stretch when pulled. When the pulling force is removed, the elastic polymers in rubber spring back to their original length. A polymer with elastic properties like this is sometimes called an elastomer. The molecular chains of an elastomer basically act like springs.
Solid materials generally expand when heated and contract when cooled. How will temperature affect the elasticity of rubber bands? You can find out for yourself with this experiment.
Terms, Concepts and Questions to Start Background Research
To do this project, you should do research that enables you to understand the following terms and concepts:
- Atom
- Molecule
- Polymer
- Elastomer
- Hooke's law
Questions
- How does the elasticity of rubber change with temperature?
Bibliography
- Explore this website to find out much more about polymers:
PSLC, 2007. "The Kids' Macrogalleria," Polymer Science Learning Center, Department of Polymer Science, University of Southern Mississippi [accessed June 15, 2007] http://www.pslc.ws/macrog/kidsmac/. - Here you can learn about the chemical structure of rubber, a natural polymer:
CHF, 2001. "Back to Nature for Polymers," The Chemical Heritage Foundation [accessed June 15, 2007] http://www.chemheritage.org/EducationalServices/FACES/poly/readings/nat.htm. - Here is a brief introduction to Hooke's Law:
Krowne, A., 2005. "Hooke's Law," PlanetPhysics.org [accessed June 15, 2007] http://planetphysics.org/encyclopedia/HookesLaw.html. - The idea for this project is by Vince Calder, from his answer on the Newton Ask A Scientist bulletin board:
Mellendorf, K., et al., 2002. "Hooke's Law and Rubber Bands," Newton Ask A Scientist, Argonne National Laboratory [accessed June 15, 2007] http://www.newton.dep.anl.gov/askasci/phy00/phy00525.htm.
Materials and Equipment
To do this experiment you will need the following materials and equipment:
- Rubber bands (six or more, all of the same size and width)
- One box of paper clips (you'll open these up into "S" shapes, to chain rubber bands together)
- Small paper cup or other container
- String or thread
- Glass beads of uniform size (from an art supply or hobby store)
- Thermometer
- Hair dryer
- Large-diameter cardboard tube, tips:
- For example, from a wrapping paper roll
- Must be long enough to enclose your chain of rubber bands, and wide enough so you can hang a paper cup at the end of the chain
- As an alternative, you could use a transparent glass or plastic tube, in which case you won't need to cut a slit in the side
- Coffee filters
- Sturdy hook, mounted on a wall or workbench, from which to hang your apparatus
- Utility knife
- Meter stick or tape measure
Experimental Procedure
- Do your background research so that you are knowledgeable about the terms, concepts, and questions, above.
- Use paper clips, unbent into an "S" shape to connect a chain of six (or more) rubber bands.
- Cut a slit along the length of the cardboard tube, and punch three small holes, equally spaced, near the top edge.
- The tube will act as an enclosure around the rubber bands to stabilize the temperature.
- The slit allows you to see inside to measure the temperature and the length of the rubber bands.
- Attach three short strings through the holes at the top of the tube, then tie them together.
- Hang the tube from the hook to enclose the rubber band chain.
- Use an open paper clip to hang the chain of rubber bands from the hook, inside the cardboard tube.
- Hang (or securely tape) a thermometer inside the cardboard tube, so that you can read the temperature through the slit in the tube.
- Make a container for the glass beads, so you can hang them from the chain of rubber bands.
- As you did with the cardboard tube, punch three small holes, equally spaced, near the top of a paper cup.
- Attach three short strings through the holes, then tie them together.
- Use an open paper clip to hang the cup from the chain of rubber bands.
- Fill the cup about half-full with glass beads (count how many you use).
- Block the bottom end of the tube with crumpled coffee filters. You'll be heating the rubber bands from the bottom of the tube using a hair dryer. The crumpled coffee filters will block direct air currents so the rubber band chain doesn't blow around. Heat will still rise into the tube to warm it up.
- Note the starting temperature inside the tube, and measure the length of the rubber band chain at room temperature.
- With the hair dryer on the low setting, blow warm air at the bottom of the tube. In order to have several different temperatures, you'll start farther away from the tube, and work your way closer.
- The temperature inside the tube will slowly rise. When it stabilizes (stops changing), write down the temperature, and then add or remove glass beads until the length of the rubber band chain is equal to the starting length (at room temperature). Write down how many beads are needed to keep the rubber band chain stretched to the initial length.
- Hold the hair dryer closer and repeat steps 8–9. See if you can get measurements for at least four different temperatures.
- If the outside temperature is much different than inside (warmer or colder), you can take your apparatus outdoors to get yet another temperature. Remember to wait for the temperature to stabilize (thermometer reading is no longer changing) before you make your measurements.
- As with any experiment, you should complete more than one trial to make sure that your results are consistent. Repeat the experiment at least three times.
- Make a table of your results like the one below:
Temperature
(°C)Length of chain
(cm)Number of glass beads - For repeated trials at a given temperature, calculate the average number of beads used to stretch the rubber band chain to the standard length at that temperature.
- Make a graph of the average number of beads used (y-axis) vs. temperature (x-axis) for each temperature tested. This graph shows the force required to keep the length of the rubber bands constant changes with temperature. Is more force or less force required as the temperature increases?
Variations
- Do rubber bands behave like springs? Use the Experimental Procedure described in the following Science Buddies project with rubber bands in place of springs in order to find out: Applying Hooke's Law: Make Your Own Spring Scale.
- Do you think that the force required to break a rubber band will change with temperature? Use a spring scale to measure the maximum force that a rubber band can withstand before breaking. Perform multiple trials with rubber bands at different initial temperatures.
- For more science project ideas in this area of science, see Mechanical Engineering Project Ideas
Credits
Andrew Olson, Ph.D., Science Buddies
Sources
The idea for this project is by Vince Calder, from his answer on the Newton Ask A Scientist bulletin board:
- Mellendorf, K., et al., 2002. "Hooke's Law and Rubber Bands," Newton Ask A Scientist, Argonne National Laboratory [accessed June 15, 2007] http://www.newton.dep.anl.gov/askasci/phy00/phy00525.htm.
Last edit date: 2007-09-25 18:00:00
