Question detail
Why does high‑density poly(ethene) have a higher melting point than low‑density poly(ethene) produced from the same monomer ethene?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
Question
Type
exam_style
Style
Topic
Using materials
Question
Why does high‑density poly(ethene) have a higher melting point than low‑density poly(ethene) produced from the same monomer ethene?
Answer
High‑density poly(ethene) has a linear structure with few branches, allowing the chains to pack tightly and form strong van der Waals forces between chains. This close packing requires more energy to disrupt, giving a higher melting point. Low‑density poly(ethene) has many branches that hinder close packing, resulting in weaker inter‑chain forces and a lower melting point.
Explanation
The answer links polymer structure to physical property (melting point), showing application of knowledge about how branching affects packing and intermolecular forces, which is required by the objective.
Common mistake
Confusing Poly(ethene) Types
Students often confuse the production processes of low density and high density poly(ethene), thinking they are produced under the same conditions.
Remember that low density poly(ethene) is produced at high temperatures and pressures, while high density poly(ethene) is produced at lower temperatures and pressures with a different catalyst.
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