Question detail
Explain how the same monomer, ethene, can give rise to both low‑density and high‑density poly(ethene) when polymerised under different conditions.
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
Explain how the same monomer, ethene, can give rise to both low‑density and high‑density poly(ethene) when polymerised under different conditions.
Answer
Low‑density poly(ethene) is produced when ethene is polymerised in the presence of a free‑radical initiator at relatively low pressure, giving a highly branched polymer. The branches prevent close packing of chains, resulting in a low density. High‑density poly(ethene) is made by polymerising ethene under high pressure and in the presence of a catalyst such as Ziegler–Natta, which gives a linear polymer with very few branches. The linear chains pack closely together, giving a higher density.
Explanation
The answer demonstrates understanding of how reaction conditions (pressure, catalyst) control polymer structure (branching) and thus density, directly addressing the learning 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.
Related flashcards
Flashcard 1 of 5
Related practice questions
Question 1 of 5
Choose an answer, get feedback, then move sideways through the set.