A chemical reaction in which simple molecules combine to form long chain molecules is called?

• A. Polymerization
• B. Crystallization
• C. Combustion
• D. Deterioration

Answer: (A)

Polymerization is a chemical reaction in which simple molecules join together to form long chain molecules. In this process, small units called monomers link up to create polymers, which are large, chain-like molecules. There are different ways this happens: addition (chain-growth) polymerization where monomers add onto a growing chain without byproducts, and condensation (step-growth) polymerization where bonds form and a small molecule such as water is released with each step. This is how everyday polymers are built, like polyethylene from ethylene or proteins from amino acids.

Crystallization, by contrast, is the process of molecules arranging into a highly ordered solid lattice, not about linking chains. Combustion is burning that rapidly reacts with oxygen, releasing heat, light, and reaction products. Deterioration refers to the gradual breaking down or degradation of materials, which is a different kind of change than building long chains.