Bring Science Home
An astounding activity from Science Buddies to stretch your ideas about physics
By Ben Finio, Science Buddieson
Key concepts
Physics
Heat
Molecules
Forces
Introduction
Have you ever noticed that some objects tend to expand when they get hot and contract when they cool down? For example, you might run hot water over the lid of a jar that's stuck—this causes the lid to expand, making it easier to twist off. Does this effect work the same way for all materials? Try this fun activity to find out!
Background
Materials are made up of atoms and molecules. (Molecules are groups of multiple atoms that are bonded together.) Even though you can't see it with the naked eye, these molecules are constantly vibrating around and bumping into one another. Normally when a material gets hotter, the molecules vibrate more intensely. Because they bump into one another harder this causes the material to expand a bit. This phenomenon is called thermal expansion, which is responsible for many of the cracks you see in roadways and sidewalks. As the temperature changes from very hot to very cold throughout the summer and winter, the materials expand and contract over and over again, eventually leading to cracks.
Rubber bands are different than many other materials because their molecules are actually very long chains, kind of like a tangled pile of spaghetti. These long chains are called polymers, which can behave in surprising ways when you heat or cool them. In this activity you will change the temperature of a rubber band using hot water and ice water. Do you think a rubber band will expand or contract when it heats up?
Materials
- Two-liter soda bottle
- Permanent marker
- Scissors
- Pencil
- Small, thin rubber band
- About 20 to 25 quarters
- Tape (any kind will work)
- Paper clip
- Hot tap water
- Ice cubes
- Large shallow bowl or pan
- Work area where it's easy to clean spills
- Dish towel or paper towels
Preparation
- Make sure you have a work area set up where you can easily clean spilled water, such as a kitchen counter.
- Use adult assistance for cutting the bottle and when using very hot tap water.
Procedure
- Have an adult use scissors to cut the top off a two-liter soda bottle, turning it into a cylinder shape.
- Use tape to cover any sharp edges around the top rim of the bottle.
- Use adult assistance to poke small holes (just large enough for a pencil to pass through) in opposite sides of the bottle using scissors, about one inch below the top edge.
- Poke the pencil through one of the holes from the outside of the bottle.
- Loop your small rubber band around the pencil.
- Continue pushing the pencil through the hole on the other side of the bottle.
- Tape together a stack of about 20 quarters, with a paper clip as a "hook" that you can use to hang them from the rubber band. How many quarters do you think your rubber band will be able to comfortably support? (The exact number of quarters you need will depend on the size and strength of your rubber band. You want the rubber band to visibly stretch out when you hang the quarters from it but not so much that it hits the bottom of the bottle. A strong rubber band may require more quarters, a weaker rubber band may require fewer.) You can try spreading the quarters out to make them easier to hang—for example, two stacks of 10 taped next to one another or four stacks of five taped next to one another—instead of one big stack of 20 quarters.
- Place your two-liter bottle into a shallow bowl or pan to catch any water that spills.
- Fill the bottle up to the pencil with hot tap water so the rubber band is completely submerged. Wait a minute or two for the rubber band to come to the same temperature as the water. What do you think might happen to the length of the rubber band?
- Look at the bottle from the side so that your eyes are level with the bottom of the rubber band. Use a permanent marker to draw a line on the side of the bottle that is even with the bottom of the rubber band, and label it "hot."
- Now, add ice cubes to the bottle and stir gently. This will cause the water level to rise, so some water will spill out of the holes you poked for the pencil.
- If the water is still very hot, the ice cubes may melt quickly. Continue adding ice cubes and stirring gently until the bottle and water feels very cold. What do you think will happen to the length of the rubber band at this new temperature?
- Look at the side of the bottle again, so your eyes are level with the bottom of the rubber band. Draw a new line that is even with the bottom of the rubber band and label it "cold."
- Is your "cold" line above or below your "hot" line? Is this what you expected to happen? Why or why not?
- Extra: You can quantify the activity by using a thermometer to measure the different water temperatures and a ruler to measure the lengths of the rubber band. If you take measurements at multiple points (for example, hot water, room-temperature water, ice water), then you can make a graph of your results.
- Extra: Try other methods of heating and cooling instead of using hot and cold water. For example, pour the water out of the bottle, and heat the rubber band with a hair dryer. Then to cool it, try leaving the bottle in your refrigerator for about half an hour. Do you get the same results when you measure the rubber band?
- Extra: Try the activity again with different rubber bands. Do some shrink or lengthen more or less than others? Why do you think that is?
Observations and results
Your results might have surprised you! The rubber band actually expands when it gets colder! This seems counterintuitive because most materials expand when they are heated and contract when they get cold. This occurs because of the unusual polymer structure of rubber. When the long chains get hotter and vibrate, they actually shorten, causing the material to contract. When the chains cool down, they relax and stretch out, causing the material to expand.
To help visualize this take any rope, string or cable you can find around the house that is a few feet long (short enough that you can hold one end of it in the air without the other end touching the floor). Hold the rope out so it hangs down straight (it is not vibrating) and observe how close the bottom end is to the floor. Now, shake your hand back and forth rapidly (to make the rope vibrate). Does the end of the rope get closer to the floor or farther away? It should get farther away as the rope "bunches up" and vibrates. The same thing happens when the polymer chains in rubber heat up and vibrate—they actually get shorter.
Cleanup
Pour the water down the drain (or use it—with permission—to water plants) and clean up any spilled water. Remove the pencil and tape from your two-liter bottle and recycle it—or save it for a future science activity!
More to explore
Heat Shrink! Why rubber bands get shorter when you heat them, from The Naked Scientist
Rubber Band Elasticity and Temperature, from Science Buddies
Science Activities for All Ages!, from Science Buddies
This activity brought to you in partnership with Science Buddies
ABOUT THE AUTHOR(S)
Ben Finio is a senior staff scientist at Science Buddies and a lecturer at the Cornell University Sibley School of Mechanical and Aerospace Engineering. Follow him on Twitter @BenFinio.
Recent Articles by Ben Finio
- Build a Recycling-Sorting Machine
- Build a Cooler
- Build a Paper Airplane Launcher
Recent Articles by Science Buddies
- Build a Recycling-Sorting Machine
- How Empty Is an Empty Bottle?
- Build a Cooler
FAQs
Does stretching a rubber band increase its temperature? ›
Rubber elasticity is an entropic phenomenon. When you stretch the elastic you force the constituent chains into a more ordered state, but you haven't stretched the chains themselves. Entropy cannot go down, so the entropy becomes thermal motion of the atoms, i.e. they get hot.
Why do rubber bands get cold when you stretch them? ›As a rubber band is stretched out, the molecules become more ordered, and warm up in a similar way to how compressing a gas causes it to heat up. Releasing the rubber band bounces it back toward a more tangled-up state, and it cools down.
What happens to rubber when it is heated? ›Polymers like rubber shrink on heating as their molecular chains curl up, and water shrinks when warmed from its freezing point to around 4°C. After that, though, it behaves normally, and expands on warming.
What changes happen when you stretch a rubber band? ›When we apply force and stretch the rubber band then it changes its shape and gets elongated. Thus, a rubber band changes its shape only under force. But after releasing the force, it moves back to its original shape due to the property of rubber called elasticity. Thus, it regains its shape when the force is removed.
Is rubber sensitive to temperature? ›Although natural rubber retains excellent physical strength and elasticity, it is highly susceptible to damage caused by extreme temperatures and environmental factors.
Does temperature affect elasticity? ›Effect of temperature on Elasticity:- As the temperature of substance increases, its elasticity decreases.
How far can a rubber band stretch without breaking? ›Some Silicone rubbers can stretch up to 1000%! (That's about 100x its original length!) Typically the softer the silicone the more it stretches, 20 shore will stretch a lot more than an 80 shore grade.
Does heat destroy rubber? ›Most elastomers undergo rubber degradation over time and the most common rubber deterioration causes are exposure to light, oxygen (ozone) and heat.
Does heat harden rubber? ›The Basics of Vulcanized Rubber
It's made via a curing process in which the rubber's elastomers harden in response to heat and sulfur. Exposure to heat and sulfur creates new cross-links in the rubber that, ultimately, makes the rubber stronger and more elastic.
Silicone rubber, unlike the majority of other rubbers, can withstand extreme temperatures way above 200°C and down to as low as -60°C without deforming.
When did the temperature of the rubber band change? ›
The rubber band first heats up as its stretched, then allowed to equilibrate back to room temperature. The rubber band cools below room temperature when the tension is released, the effect is large enough to be noticed by touch.
Does the volume of a rubber band change when stretched? ›The decrease in volume of rubber on stretching is influenced by the same considerations as the X-ray diffraction, since it is observed only above a certain critical elongation and is greater the higher the elongation, the lower the temperature, and the longer the time the sample is kept stretched.
What temperature can rubber withstand? ›Its resistance to solvents and petroleum products is about the same as natural rubber. Water resistance is better. Without special additives, it is vulnerable to ozone, oxygen and sunlight. Useful temperature range is -67° F to +180° F (-55° C to +82° C).
What temperature does rubber degrade at? ›...
Welcome to our Rubber Temperature Range section.
| Elastomer | Low F | High F |
|---|---|---|
| Buna-N (Nitrile) | -40 | 250 |
| Butadiene, Styrene Butadiene | -50 | 212 |
| Butyl | -50 | 250 |
| Chloroprene (Neoprene®) | -45 | 260 |
Well-vulcanized rubber does not crystallize, but loses its ability to retract when stretched. Crude or elastic rubber, however, loses elasticity completely if cooled to 70-80° F. below zero. If bent suddenly at right angles a glass-like breakage occurs.
Can you make a rubber band stronger? ›Working with researchers at the University of Sussex, Alliance is adding graphene to rubber bands. By doing so, the bands become up to 200-times stronger than steel, rendering them pretty much unbreakable. But that's just the first big advantage.
What happens when you put too much tension on a rubber band? ›A rubber band's purpose is to hold objects together using tension. But with too little tension, the rubber band flops. With too much, the rubber band snaps. This principle is also true in organizations.
Can rubber stretch permanently? ›When stretched out, rubber pulls back hard to return to its original shape. It's pretty resilient stuff! Of course, you'll find that if you leave a rubber band wrapped around something long enough—say, a year or two—it will eventually stretch out permanently and may even snap.
What factors affect the elasticity of a rubber band? ›Rubber bands in general stretch more in the presence of heat as Frye states, “rubber contracts when it gets colder. The molecules in the rubber band get closer together. This affects the elasticity…” This means that the band will not be able to stretch as far or support as much weight.
How does cold temperature affect elasticity? ›Yes--a rubber band will actually become softer, or easier to stretch, when the temperature gets colder. The way to think of the elasticity is in terms of entropy, which is basically a measure of disorder.
Do rubber bands lose elasticity? ›
Rubber bands wear out over time and also tend to lose their elasticity due to frequent washing as the softeners dissolve.
What happens if I dont wear my elastics for 3 days? ›Failure to wear your elastics full time or as instructed will lengthen your treatment time and will make it more difficult to achieve an optimal result. It's normal for your mouth, teeth, and jaws to be a little sore for the first few days to a week of wear.
How many times can you stretch a rubber band? ›Rubber elasticity refers to a property of crosslinked rubber: it can be stretched by up to a factor of 10 from its original length and, when released, returns very nearly to its original length. This can be repeated many times with no apparent degradation to the rubber.
How long do bands take to close gaps? ›How long does it take? If you're trying to fix your gap teeth with teeth gap bands, this process typically takes several weeks to a few months to complete. The timeline of the process usually is proportional to how large the gap between your teeth is initially.
Do rubber bands freeze? ›The technical answer is, no, rubber cannot freeze… .. however it does get hard and brittle. The scientific definition of to freeze involves a phase shift of liquid into solid forming crystals.
Why do rubber bands feel tighter than other braces? ›Answer: Elastics
I would recommend you discuss this with your doctor, but in my experience the distance that teeth needing to be shifted by elastics could be different from one side to the other. This means that one rubber band feels tighter than the other.
Cold stretching is performed by pressurizing a vessel to a specific pressure and maintaining the pressure for a moment to produce a certain amount of plastic deformation, so that the yield strength of the vessel material could be strengthened after releasing the pressure.
What kind of energy is stored in a stretched rubber band? ›Elastic Potential Energy
A stretched rubber band has the potential to do work or change things. This form of energy is called elastic potential energy. It occurs when an object (such as our skin, a spring, a trampoline, or a rubber band) resists being stretched out of shape.
The hardening of rubber at low temperatures is one of the well-known physical characteristics of rubber. The loss of elasticity of raw rubber by hardening at 0° to 10° C., its turning to the consistency of glass, and its fragility at −19° C.
Does rubber crack in cold weather? ›Even if you have new tires on your car, you can still run the risk of having them damaged when you drive in cold weather. Usually, cold temperatures make the rubber used to make the tires rigid. This makes the tire lose elasticity which makes it easy for your tires to crack.
What happens if I don't wear my rubber bands for 2 days? ›
Their effectiveness is completely based on compliance. If you don't wear them for the prescribed amount of time and change them as directed, your teeth will relapse and you could make your orthodontic treatment last longer.
Is rubber bands the last step in braces? ›This can be the last phase, so if you are wondering, “are elastics the last stage of braces,” the answer is “yes” if your braces are there to also help with bite correction. Now, if your bands are there to help move your teeth, you may need to start using them during the earlier phases of this treatment.
Should you stretch warm or cold? ›You may hurt yourself if you stretch cold muscles. Before stretching, warm up with light walking, jogging or biking at low intensity for 5 to 10 minutes. Even better, stretch after your workout when your muscles are warm.
Is it better to ice then stretch? ›Ice Your Pain
If the pain is chronic, here's the best postrun sequence: Foam roll, static stretch, ice. But for acute pain, skip rolling and stretching, and ice immediately. "The quicker you ice, the faster you slow down inflammation, the faster you begin to heal," Buraglio says.
It is not a good idea to attempt to stretch before your muscles are warm (something which the general warm-up accomplishes). Warming up can do more than just loosen stiff muscles; when done properly, it can actually improve performance.
Does a stretched rubber has increased potential energy? ›Due to stretching, a potential energy is stored in the rubber band which is released on releasing the rubber. Thus, potential energy is increased.
Is stretching a rubber band physical or chemical change? ›Stretching of a rubber band is a physical change since only the shape and size of a rubber band is changing and there is no formation of a new substance.
What type of force is a rubber band? ›Rubber bands and springs are examples of elastic materials. An elastic force is a force exerted by an object trying to return to its original shape.