Just around everyone has actually used rubber bands, but few people have taken the time to observe the less apparent properties the these day-to-day objects. In this activity you will examine the thermal properties the rubber, that is, the behavior of rubber as it relates come heat, a kind of energy.

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In the very first experiment you will certainly attempt come detect heat flow into or out of a rubber band. To execute this,you require a rather sensitive heat detector. Fortunately, you have such a detector v you at every times.Surely, you"ve feeling the warmth of a fire or the cold the an ice cube. Therefore, you recognize that her skin issensitive to heat flow. In this experiment, you will certainly detect heat flow using few of your most sensitiveskin, that on your forehead or on her lips.

Place her thumbs v the hefty rubber band, one on each end. Without extending the band, hold it to your forehead or lip. Does the band feeling cool or heat or around the very same as your skin? Repeat the test several times until you room sure the the result. relocate the rubber tape slightly away from your face, so the is not poignant your skin. Quickly stretch the band around as much as you have the right to and, holding the in the stretched position, touch the again to your forehead or lip. Go it feel warmer or cooler or about the exact same as that did when it to be relaxed? move the stretched rubber band away from girlfriend face. Conveniently let that relax come its initial size and also again hold it to her skin. Does that feel warmth or cool? Repeat the stretching and also testing, and also relaxing and also testing number of times until you are sure the the results.

An object feels cool or cold come you when warm flows from your skin come the object. Conversely, things feels warmth or warm when warmth flows native the object right into your skin. If the stretched rubber tape feels cool, climate it absorbs warm from your skin. If the feels warm, climate it gives off warmth to her skin. If the tape feels neither heat nor cool, climate there is no detectable warmth flow. These three situations can be represented as follows:
Case 1. tranquil Band + warm stretched Band Case 2. relaxed Band stretched Band + warmth Case 3. serene Band extended Band (No Heat)
Which the these 3 cases finest describes what you observed?
There is another means to test which the the three statements is correct. We can see what wake up to thelength of a rubber band if we heat or cool it.
cave one end of the rubber tape from the wall surface or ceiling and suspend a weight from the other finish of the rubber band. (What you use for a weight will rely on what is available. The weight should be heavy sufficient to stretch the rubber band, but not so heavy that that is most likely to break the band. Because that example, hang the band over a door knob and also suspend a hammer indigenous the band.) warm the rubber band with a hair dryer. Start the dryer and, once it has warmed up, revolve its heat on the stretched rubber band. Go the stretched rubber band come to be longer or shorter when the is heated?
Does this monitoring agree with what you discovered in the an initial part that the experiment? law an experiment numerous ways and checking for agreement in the results is an important strategy in science.

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When rubber is heated it behaves in different way than most acquainted materials. Most materials expandwhen they room heated. Think about the liquid in a thermometer. The thermometer works since the liquidexpands once its temperature increases. Similarly, a cable made of metal, such together copper, i do not care longeras it it s okay hotter. The growth of steels with raising temperature is the principle behind thefunctioning of home thermostats and also of jumping discs.
Whether a material increases or contracts as soon as it is boil is mainly a as result of the structure of the molecule it is made of. When power is included to a material, it is distributed throughout the product and, ~ above average, each atom or molecule will have much more energy and also will be moving more energetically 보다 it was prior to the power was added. In materials made up of small, compact molecules, e.g., the liquid in a thermometer, together the molecule move about more, they press their neighboring molecules away. Rubber, top top the various other hand, contains an extremely large, threadlike molecules. As soon as rubber is heated, part of the molecules relocate about more vigorously. In order for one component of the molecule to move an ext vigorously as it is heated, it have to pull its bordering parts closer. Come visualize this, think the a molecule that the extended rubber band together a item of string set out straight on a table. Heating the stretched rubber band causes segments that the molecule to move more vigorously, which deserve to be stood for by wiggling the middle of the string earlier and forth. Together the center of the string moves, the end of the string obtain closer together. In a similar fashion, the end of the rubber molecules acquire a bit closer together the rubber is heated, leading to the extended rubber tape to contract.

After Prof. Shakhashiri prove this experiment in one of his live shows, one attendee sent him this picture. "The children grabbed rubber bands as soon as they gained home, to experience the warmed-when-stretched phenomenon."
For extr information, see CHEMICAL DEMONSTRATIONS: A Handbook for Teachers that Chemistry, Volume 1, by Bassam Z. Shakhashiri, The college of Wisconsin Press.Back to home Experiments