A Level Chemistry OCR Practice Exam

The process of addition polymerization specifically involves the formation of long-chain molecules, known as polymers, from monomers that are typically unsaturated compounds, such as alkenes. During this process, the double bonds present in the alkene monomers open up, allowing these monomers to link together to form a saturated molecular chain. This results in a polymer that possesses a repeated structural unit derived from the original monomer.

This understanding highlights how addition polymerization is fundamentally about creating a larger, more complex structure from simpler unsaturated molecules, thereby converting them into a saturated form by breaking the multiple bonds in the process. The context of the question refers to the transformation from individual unsaturated monomers to a continuous polymer chain, which makes option A an accurate description of the addition polymerization process.

The other choices, though mentioning relevant chemistry concepts, do not accurately describe the specific nature of addition polymerization. For instance, forming a saturated molecule from an unsaturated one can happen through reactions not limited to polymerization. The attachment of a gas to a solid refers to adsorption, which is unrelated to polymerization. Furthermore, hydrocarbons joining in a ring structure relates to cyclization, a different chemical concept.