Which process joins small hydrocarbons to form larger molecules?

Which process joins small hydrocarbons to form larger molecules?

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

Answer: (A)

Joining small hydrocarbon units into larger molecules happens through addition polymerization. In this process, monomers—often unsaturated hydrocarbons like ethene—open their double bonds and link end-to-end to build long chains, forming polymers such as polyethylene. This is how small, simple molecules become large, repeating structures. Other processes do different things. Cracking splits large molecules into smaller ones, so it reduces molecular size. Fractional distillation separates mixtures into components based on boiling points, without forming new bonds. Reforming rearranges the carbon skeletons of molecules to improve fuel properties, rather than building longer chains. So, the method that creates larger molecules from smaller ones is addition polymerization.

Joining small hydrocarbon units into larger molecules happens through addition polymerization. In this process, monomers—often unsaturated hydrocarbons like ethene—open their double bonds and link end-to-end to build long chains, forming polymers such as polyethylene. This is how small, simple molecules become large, repeating structures.

Other processes do different things. Cracking splits large molecules into smaller ones, so it reduces molecular size. Fractional distillation separates mixtures into components based on boiling points, without forming new bonds. Reforming rearranges the carbon skeletons of molecules to improve fuel properties, rather than building longer chains. So, the method that creates larger molecules from smaller ones is addition polymerization.