Which term describes the process in which a small molecule is released during polymerization?

• A. Fractional distillation
• B. Condensation polymerization
• C. Addition polymerization
• D. Cracking

Answer: (B)

Releasing a small molecule during polymerization points to condensation polymerization. In this type of polymerization, monomers with two or more reactive groups join and a small molecule—commonly water, methanol, or hydrogen chloride—is eliminated with each bond formed. This step-growth process builds the polymer while byproducts are given off, which is the hallmark of condensation polymerization. For example, forming a polyester from a diol and a diacid releases water; similarly, polyamides like nylon involve byproduct water or HCl depending on the route.

In contrast, addition polymerization builds long chains by adding monomers across a double (or triple) bond without releasing small molecules, so no byproduct is formed. The other terms describe processes unrelated to polymerization with byproduct release: fractional distillation separates mixtures by boiling points, and cracking breaks large hydrocarbon molecules into smaller ones using heat.