Hello Ray! Experimenting with Rubber Bands (Part Two) – CBS Pittsburgh

PITTSBURGH (KDKA) — Last time we showed you an interesting rubber band, or as we call it “rubber band” science, where you heat up when you stretch.

(Image credit: Ray Petelin)

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This week we’re going to find out what happens when you add heat to a stretched rubber band, and just to “let the cat out of the bag” it will likely be the opposite of what you think!

(Image credit: Ray Petelin)

To do this, we attach a weight to a rubber band. Here we used a partially filled water bottle. We clamped the elastic to our counter and we want the elastics to stretch, but we also want it to stay suspended off the floor.

(Image credit: Ray Petelin)

So we have reference points for this experiment, we drew some lines on a piece of old cardboard.

(Image credit: Ray Petelin)

At this point we will use the hair dryer to heat the elastic.

Well what do you think will happen?

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(Image credit: Ray Petelin)

By adding heat to the elastic, it shrinks and our weight rises! Many things expand when heated, but in the case of polymers or molecular chains, shrinkage occurs.

(Image credit: Ray Petelin)

Remember that the polymers in rubber when stretched are like chain lines.

(Image credit: Ray Petelin)

When these polymer chains are stretched and heated even more, they begin to vibrate. As these chains vibrate, they become shorter, causing the rubber bands to tighten or shrink. This will raise the water bottle!.

(Image credit: Ray Petelin)

This is just another complex thing about a seemingly simple rubber band!

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(Image credit: Ray Petelin)