sci_chem
Polymers
Chapter summary, hard words and model exam answers for ICSE Class 10 Hindi.
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Chemistry · CBSE 10 · ICSE 10 · GCSE (AQA, Edexcel, OCR)
Summary
Polymers are giant molecules built from thousands of small repeating units called monomers. Natural ones include starch and proteins; synthetic ones are the plastics.
Ethene (CH2=CH2) gives poly(ethene). The repeat unit is (-CH2-CH2-)n. No other product is ever formed.
A diol plus a dicarboxylic acid makes polyester; a diamine plus a diacid makes nylon. Each new link releases water.
Thermoplastics like poly(ethene) melt and remould. Thermosetting polymers have covalent cross-links, so they char rather than soften and cannot be recycled.
Hard words & meanings
| polymer | a giant molecule made of many small repeating units joined in a chain |
| monomer | the small molecule that links with others to build a polymer |
| addition polymerisation | alkene monomers join by opening their C=C double bonds with no other product |
| condensation polymerisation | monomers with two functional groups join, losing a small molecule (usually water) |
| repeat unit | the smallest section of a polymer that repeats, drawn in brackets with subscript n |
| thermoplastic | a polymer with weak forces between chains that softens and remoulds on heating |
| thermosetting polymer | a polymer with covalent cross-links forming a rigid network that never softens |
| biodegradable | able to be broken down by microorganisms into simpler substances |
Model exam answers, grammar & audio
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