A Level Chemistry OCR Practice Exam

In addition polymerization, the process involves the formation of long chains of polymer from individual unsaturated alkene monomers, which contain double bonds. During this process, these double bonds in the alkene react to form single bonds as the monomers link together in a repetitive manner, resulting in a very long molecular chain. This reaction typically does not produce any byproducts, making it a straightforward method of synthesizing polymers like polyethylene or polypropylene.

The other options do not accurately describe the process of addition polymerization. Short carbon chains are not characteristic of this kind of polymerization since the end product is a long polymer chain. The description of forming a long polymer chain from saturated compounds does not align with addition polymerization, which specifically involves the reaction of unsaturated monomers. Fragmentation producing small molecules is more related to other chemical processes rather than the continuous addition of monomers in polymerization. Thus, the key characteristic of addition polymerization being highlighted here is the transformation of unsaturated alkene monomers into a long chain without byproducts, which aligns perfectly with the correct answer.