Which of the following is an example of a condensation reaction?

• A. Nylon
• B. Ethanol
• C. Methane
• D. Water

Answer: (A)

A condensation reaction is when two molecules join to form a larger molecule with the loss of a small molecule, usually water. In polymerization, many small monomers link up, and water is released each time a new bond forms.

Nylon fits this idea because it is made by linking a diamine with a diacid to form amide bonds, and each linking step releases water. That pattern—monomers joining with loss of water to make a larger molecule—is the hallmark of a condensation reaction, used here in making a polymer.

EthanoL, by contrast, comes from the hydration of ethene, which is an addition reaction where atoms are added across a double bond rather than two molecules joining with water loss. Methane isn’t formed by a condensation-type process, and water is a product of many condensation reactions rather than an example of the reaction itself.