Why does rubber stretch and return?

Answer: Long polymer chains coil and uncoil

Rubber full of tiny air bubbles — Wrong. Rubber's elasticity comes from its molecular structure, not air. Rubber consists of long, coiled polymer chains (polyisoprene). When stretched, chains straighten; when released, they coil back up. This molecular behavior creates elasticity.

Rubber molecules are very small — Wrong. Rubber molecules are actually very long polymer chains (polyisoprene). Elasticity comes from these long chains being coiled—they straighten when stretched and spring back when released. Long chains, not small molecules, create rubber's unique properties.

Long polymer chains coil and uncoil ✓ — Correct! Rubber is made of long, tangled polymer chains (polyisoprene). These chains naturally coil up randomly. When you stretch rubber, you straighten the chains. When released, entropy (natural disorder) causes chains to coil back up, returning rubber to its original shape. Vulcanization (adding sulfur) creates cross-links between chains, improving elasticity and durability.