ymbol represented by the letter $B$.","location":"specification"}]}]}],"generatedAt":"2026-07-21T04:24:38.464Z","modelVersion":"gpt-5.6-terra","explanationVersion":"v3"},"options":[]},{"id":"85c630e3-a21c-447d-8fdd-80dc980fd9bf","label":"b","content":"Poly(phenylethene) is classified as a thermosoftening polymer. Contrast the structural features of thermosoftening polymers like poly(phenylethene) with thermosetting polymers, and explain how this structural difference affects their response to heating.","markscheme":"- Explains that thermosoftening polymers consist of individual/separate polymer chains held together by weak intermolecular forces with no cross-links, whereas thermosetting polymers contain strong covalent cross-links between chains M1\n- Explains that upon heating, the weak intermolecular forces in thermosoftening polymers are easily overcome (allowing chains to slide and melt/be reshaped), whereas the covalent cross-links in thermosetting polymers do not break on heating, causing them to char or decompose rather than melt A1","marks":2,"order":1,"markingRubric":null,"explanation":{"methods":[{"id":"compare_polymer_structures","label":"Compare the polymer structures","steps":[{"type":"text","order":1,"title":"Describe separate chains","content":"Start with poly(phenylethene): it has **individual, separate polymer chains**. There are **no covalent cross-links** joining one chain to another; instead, the chains are held together by weak intermolecular forces.","highlights":[{"text":"Poly(phenylethene) is classified as a thermosoftening polymer.","location":"specification"}]},{"type":"text","order":2,"title":"Compare cross-links","content":"In a thermosetting polymer, the chains are joined together by **strong covalent cross-links**. Together with the separate, non-cross-linked chains in a thermosoftening polymer, this completed structural contrast earns **M1**.","highlights":[{"text":"Contrast the structural features of thermosoftening polymers like poly(phenylethene) with thermosetting polymers","location":"specification"}]},{"type":"text","order":3,"title":"Heat thermosoftening polymer","content":"When a thermosoftening polymer is heated, the weak intermolecular forces between its chains are overcome. The separate chains can then slide past each other, so the polymer **melts** and can be **reshaped**.","highlights":[{"text":"explain how this structural difference affects their response to heating.","location":"specification"}]},{"type":"text","order":4,"title":"Contrast heating responses","content":"In a thermosetting polymer, heating does not break the strong covalent cross-links between chains. The polymer therefore does **not** melt; it **chars or decomposes** instead. This full contrast in heating behaviour earns **A1**.","highlights":[{"text":"explain how this structural difference affects their response to heating.","location":"specification"}]}]}],"generatedAt":"2026-07-21T04:26:37.628Z","modelVersion":"gpt-5.6-terra","explanationVersion":"v3"},"options":[]},{"id":"4f5340a4-cf79-45ac-bcd3-7fd97f8baae1","label":"c","content":"Rigid plastic items like water bottles are often made from high-density poly(ethene) (HDPE), whereas flexible plastic squeeze bottles are made from low-density poly(ethene) (LDPE). Explain, in terms of their structures and intermolecular forces, why HDPE has a significantly higher density and melting point than LDPE.","markscheme":"- States that HDPE consists of straight, unbranched polymer chains, whereas LDPE consists of highly branched polymer chains B1\n- Explains that unbranched chains in HDPE can pack much more closely together than the branched chains of LDPE, leading to higher density (more mass in a given volume) M1\n- Explains that the closer packing in HDPE results in stronger/more intermolecular (van der Waals) forces between chains, which require more energy to overcome, resulting in a higher melting point A1","marks":3,"order":2,"markingRubric":null,"explanation":{"methods":[{"id":"structure_

Organic chemistry

Question 30

Organic chemistry Questions

Organic chemistry

Question 30

Organic chemistry Questions