The World Around Us

Chemicals in Our World

What makes a rubber band stretchy?

Rubber bands are made up of long, tangled-up, chainlike molecules called polymers. These long chains prefer to be tangled up because it maximizes their entropy or just the number of ways they can arrange themselves (see “Physical and Theoretical Chemistry” for more on entropy or “Polymer Chemistry” for more on polymers). When we stretch a rubber band, it straightens out these long chain molecules into a state with less entropy, so basically there are fewer stretched-out conformations possible than there are tangled-up ones. When we release the rubber band, it contracts to a more disordered state, primarily just because there are more possible conformations associated with the contracted length.


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