A Level Chemistry OCR Practice Exam

What process involves multiple unsaturated alkene molecules adding to form a polymer?

1. Condensation polymerization

2. Chain growth polymerization

3. Addition polymerization

4. Step growth polymerization

The correct answer is: Addition polymerization

The process of multiple unsaturated alkene molecules adding together to form a polymer is known as addition polymerization. In this reaction, the double bonds of unsaturated alkenes are broken and new single bonds are formed, linking the monomer units together into long chains. This process typically involves the initiation, propagation, and termination stages, where the reaction starts with an initiator that forms radicals, which then react with the alkene, allowing the chain to grow. This method is particularly effective for alkenes because the reactive nature of the double bond facilitates the continuous addition of more monomers, leading to the formation of high molecular weight polymers. Addition polymerization is commonly used for the synthesis of polymers such as polyethylene, polystyrene, and polyvinyl chloride (PVC).