Assessment and Qualifications Alliance (AQA) GCSE Biology Paper 2 Practice Exam

The production of high density poly(ethene) (HDPE) is characterized by its molecular structure, which allows the polymer chains to line up more closely. This is because HDPE is typically produced using a low-pressure process and has a linear structure with minimal branching. The closely packed chains in HDPE contribute to its strength and rigidity, making it suitable for applications that require high tensile strength and durability.

In contrast, other options are not characteristic of HDPE. The application of heat in the production process varies, and while molecular weight can differ between types of poly(ethene), the defining feature of HDPE is its chain structure rather than merely its molecular weight or the amount of heat applied. The presence of fewer branching points in HDPE compared to low density poly(ethene) (LDPE) further enhances its packing efficiency, contributing to the overall properties that distinguish HDPE.